wood is good - user oriented material, technology and design

October 18th

2013

ZAGREBCROATIA UNIVERSITY OF ZAGREB

FACULTY OF FORESTRYINNOVAWOOD

October 18th, 2013ZAGREB, CROATIA

WOOD IS GOOD - USER ORIENTED MATERIAL, TECHNOLOGY AND DESIGN

24th International Scientific Conference

ORGANISERSORGANISERSORGANISERSORGANISERS

INNOVAWOOD

FACULTY OF FORESTRY ZAGREB

WOOD SCIENCE AND TECHNOLOGY DEPARTMENT, BIOTECHNICAL FACULTY,

LJUBLJANA UNIVERSITY

ZAGREB FAIR

CROATIAN FORESTRY SOCIETY

SLOVENIAN ASSOCIATION OF WOOD TECHNOLOGISTS

THE SCIENTIFIC COUNCIL FOR AGRICULTURE AND FORESTRY – CROATIAN ACADEMY OF

SCIENCES AND ARTS

CROATIAN ACADEMY OF ENGINEERING

ACADEMY OF FORESTRY

CROATIAN CHAMBER OF ENGINEERS OF FORESTRY AND WOOD TECHNOLOGY

SUPPORTED BYSUPPORTED BYSUPPORTED BYSUPPORTED BY

MINISTRY OF AGRICULTURE

COCOCOCO----SPONSORSHIPSPONSORSHIPSPONSORSHIPSPONSORSHIP

MINISTRY OF ENTREPRENEURSHIP AND CRAFTS

CROATIAN FOREST RESEARCH INSTITUTE

CROATIAN FORESTS d.o.o.

CROATIAN CHAMBER OF ENGINEERS OF FORESTRY AND WOOD TECHNOLOGY

CROATIAN CHAMBER OF ECONOMY

CROATIAN CHAMBER OF ECONOMY - ZAGREB

ZAGREB COUNTY

VIROVITICA-PODRAVINA COUNTY

UNIVERSITY OF ZAGREBUNIVERSITY OF ZAGREBUNIVERSITY OF ZAGREBUNIVERSITY OF ZAGREB FACULTY OF FORESTRYFACULTY OF FORESTRYFACULTY OF FORESTRYFACULTY OF FORESTRY

INNOVAWOODINNOVAWOODINNOVAWOODINNOVAWOOD

ZAGREB FAIRZAGREB FAIRZAGREB FAIRZAGREB FAIR

24th International Scientific Conference

WOOD IS GOOD – USER ORIENTED MATERIAL, TECHNOLOGY AND DESIGN

PROCEEDINGSPROCEEDINGSPROCEEDINGSPROCEEDINGS

ZagZagZagZagreb 1reb 1reb 1reb 18888tttthhhh of October 201of October 201of October 201of October 2013333

A CIP catalogue record for this book is available A CIP catalogue record for this book is available A CIP catalogue record for this book is available A CIP catalogue record for this book is available inininin the the the the Online Catalogue of the Online Catalogue of the Online Catalogue of the Online Catalogue of the National and University National and University National and University National and University LibraryLibraryLibraryLibrary

in Zagreb in Zagreb in Zagreb in Zagreb asasasas 855287855287855287855287

PublisherPublisherPublisherPublisher:::: FACULTY OF FORESTRY, ZAGREB UNIVERSITY

OrganizOrganizOrganizOrganizersersersers::::

INNOVAWOOD FACULTY OF FORESTRY ZAGREB

WOOD SCIENCE AND TECHNOLOGY DEPARTMENT, BIOTECHNICAL FACULTY, LJUBLJANA UNIVERSITY ZAGREB FAIR

CROATIAN FORESTRY SOCIETY SLOVENIAN ASSOCIATION OF WOOD TECHNOLOGISTS

THE SCIENTIFIC COUNCIL FOR AGRICULTURE AND FORESTRY – CROATIAN ACADEMY OF SCIENCES AND ARTS CROATIAN ACADEMY OF ENGINEERING

ACADEMY OF FORESTRY CROATIAN CHAMBER OF ENGINEERS OF FORESTRY AND WOOD TECHNOLOGY

OrganizOrganizOrganizOrganizing committeeing committeeing committeeing committee::::

Professor Marian Babiak, PhD (Slovakia), Assistant Professor Christian Brischke, PhD (Germany), Mariano Perez Campos, PhD (Spain), Damir Felak, BSc (Croatia), Professor Ivica Grbac, PhD (Croatia), Associated Professor Miha Humar, PhD (Slovenia), Ivan Ištok, BSc (Croatia), Associated Professor Vassil Jivkov, PhD (Bulgaria), Nada Banek, MSc (Croatia), Petar Jurjević, MSc (Croatia), Borut Kričej, univ. BSc (Slovenia), Professor Trajče Manev, PhD (Macedonia), Associated Professor Assia Marinova, PhD (Bulgaria), Božica Marković, BSc (Croatia), Academic Slavko Matić, PhD (Croatia), Professor Milan Oršanić, PhD (Croatia), Professor Marko Petrič, PhD (Slovenia), Professor Jerzy Smardzewski, PhD (Poland), Milan Trbojević (Croatia), Mr. Gus Verhaeghe, (Belgium), Nikica Šprem, PhD (Croatia), Professor Joris Van Acker (Belgium), Dijana Vuletić, PhD (Croatia), Associated Professor Silvana Prekrat, PhD (Croatia), Professor Stjepan Pervan, PhD (Croatia), Professor Vladimir Andročec (Croatia)

EditorEditorEditorEditor----inininin----chiefchiefchiefchief::::

Professor Ivica Grbac, PhD

AssistantAssistantAssistantAssistantssss to Editorto Editorto Editorto Editor----inininin----chief:chief:chief:chief: Professor Stjepan Pervan, PhD

Associate Professor Silvana Prekrat, PhD

Technical editorTechnical editorTechnical editorTechnical editor:::: Miljenko Klarić, MEng in Wood Technology

Cover design:Cover design:Cover design:Cover design:

Associate Professor Silvana Prekrat, PhD Professor Stjepan Pervan, PhD

Miljenko Klarić, MEng in Wood Technology

ProgramProgramProgramProgramme committee and reviewers:me committee and reviewers:me committee and reviewers:me committee and reviewers: Professor Andrija Bogner, PhD (Croatia), Professor Stanislaw Dziegielewski, PhD (Poland), Professor Ivica Grbac, PhD (Croatia), Professor Vladimir Jambreković, PhD (Croatia), Professor Vlatka Jirouš-Rajković, PhD (Croatia), Associated Professor Vassil Jivkov, PhD (Bulgaria), Professor Boris Ljuljka, PhD (Croatia), Professor Marko Petrič, PhD (Slovenia), Professor Andreas Rapp, PhD (Germany), Professor Milan Šernek, PhD (Slovenia), Associated Professor Silvana Prekrat, PhD (Croatia), Professor Stjepan Pervan, PhD (Croatia)

EDITIONEDITIONEDITIONEDITION 200 copies

ISBN: 978-953-292-031-4

FOREWORDFOREWORDFOREWORDFOREWORD

Although the profit and how it will be provided will stay in this time of crisis one of main topics, this year’s conference “WOOD IS GOOD – USER ORIENTED MATERIAL, TECHNOLOGY AND DESIGN” draws attention to the end user as a vital participant in creating profitable products. Attention is still focused on to the still large number of products that are focused only on profit, which in long term will cause loss to the society.

Creative potentials are opened for new insights and innovative processes, whose

primary goal is adjustment to the customer and environment, and their main task has to be a conscious conservation of the environment and natural resources. These are the preconditions for the increase of competitiveness and flexibility of all industrial branches in both the world and the Croatian wood processing industries.

Proceedings of this conference is a great source of answers to questions about the

new achievements in the field of design, construction, economics, ergonomics, wood and non-wood materials and their properties. Papers in proceedings are outcome studies of domestic and foreign experts in wood technology, economics, ergonomics and design, who wanted to draw attention to the end user and their needs in the design, selection of materials and technologies of designed products.

The concept of sustainable development as the vital concept of the economic

development strategy of modern Europe and the European Union is based on creating a competitive market of knowledge, research processes and experiences. This concept aims at better social relations, prevention of effects of serious climate changes, preservation of nature and creation of healthy environment.

By accessing to the European Union, in this year the Croatian forestry and wood

processing sector in cooperation with INNOVAWOOD organisation will be connected with countries that have experience of designing and manufacturing products based on meaningful synergy interdisciplinary work of various experts focused on users without neglecting the profit as the basis for market survival.

Joining the European Union this year will provide new possibilities to Croatian

forestry and wood processing sectors for a better development in the future

Professor Ivica Grbac, PhD

CONTENTSCONTENTSCONTENTSCONTENTS

1. 1. 1. 1. BARBOUTIS Ioannis – KAMPERIDOU Vasiliki :::: KLISMOS - THE STYLE AND FORM OF THE ANCIENT GREEK CHAIR

1

2. 2. 2. 2. DOMLJAN Danijela – VLAOVI Ć Zoran – ŽUPČIĆ Ivica – ŽIVKOVI Ć Vjekoslav – JIROUŠ-RAJKOVI Ć Vlatka – GRBAC Ivica: QUALITY OF THE WOODEN PRODUCTS FOR DESIGN AND EQUIPPING EDUCATIONAL INSTITUTIONS

9

3. 3. 3. 3. ESEN Raşit – YAPICI Fatih :::: THE EFFECTS OF PRESS TIME AND PRESS PRESSURE ON THE SCREW STRENGTH PROPERTIES OF ORIENTED STRENGTH BOARD (OSB) MANUFACTURED FROM POPLAR WOOD

15

4444. . . . FABISIAK Beata – KŁOS Robert – MAĆKOWIAK Katarzyna :::: ANALYSIS OF USER PREFERENCES CONCERNING E-TREND IN KITCHEN FURNITURE DESIGN

19

5. 5. 5. 5. GORNIK BUČAR Dominika – MERHAR Miran – GOSPODARI Č Bojan:::: INFLUENCE OF TOOL WEAR ON THE QUALITY OF THE NEWLY FORMED SURFACE IN THE DRILLING OF WOOD COMPOSITES

29

6. 6. 6. 6. GRLADINOVI Ć Tomislav – PERIĆ Ivana – STASIAK-BETLEJEWSKA Renata – ŠKODA Petar:::: INCREASING THE PRODUCTIVITY OF ENTERPRISES WITH THE 20 KEYS METHOD

35

7. 7. 7. 7. HROVATIN Jasna – VIŽINTIN Jože :::: KITCHEN FURNITURE - ACCESSIBILITY OF STORAGE AND WORKING SPACE

41

8.8.8.8. JIVKOV Vassil – SIMEONOVA Ralitsa – MARINOVA Assia – GRADESVA Galina :::: STUDY ON THE GLUING ABILITIES OF SOLID SURFACE COMPOSITES WITH DIFFERENT WOOD BASED MATERIALS AND FOAM PVC

49

9. 9. 9. 9. KAMPERIDOU Vasiliki – BARBOUTIS Ioannis :::: LATHE TOOL - IT’S DEVELOPMENT FROM THE ANCIENT TIMES TO NOWADAYS

57

10. 10. 10. 10. KITEK KUZMAN Manja – ŠERNEK Milan – KARIŽ Mirko :::: DESIGN AND MANUFACTURING OF ORGANIC SHAPE FURNITURE

65

11. 11. 11. 11. KLARI Ć Miljenko – PERVAN Stjepan:::: IMPORTANCE OF BOTANICAL BINOMINAL NOMENCLATURE FOR HYDROTHERMAL WOOD PROCESSING

71

12. 12. 12. 12. KUTNAR Andreja – KUŠAR Tomaž – KITEK KUZMAN Manja :::: ENVIRONMENTAL IMPACT ASSESSMENT AS PART OF FURNITURE DESIGN

81

13. 13. 13. 13. KYUCHUKOV Georgi – GRUEVSKI Georgi – MARINOVA Assia – KYUCHUKOV Borislav – JIVKOV Vassil :::: COMPARATIVE ANALYSIS OF STIFFNESS COEFFICIENTS OF END AND T-SHAPE CORNER JOINTS OF FRAME STRUCTURAL ELEMENTS WITH TWO TYPES OF CROSS SECTIONS MADE OF SWEET CHESTNUT WOOD

87

14. 14. 14. 14. MIKLE ČIĆ Josip – JIROUŠ-RAJKOVIĆ Vlatka – ŠPOLJAR Marin :::: DURABILITY OF WATERBORNE COATING SYSTEMS FOR WOODEN WINDOWS

95

15. 15. 15. 15. NESTOROVIĆ Biserka – GRBAC Ivica – NESTOROVIĆ Predrag:::: NUMERICAL ANALYSIS OF LAMINATED WOOD STRUCTURES - CHAIRS BY APPLICATION OF FEA

101

16. 16. 16. 16. PALIJA Tanja – VU ČKOVI Ć Aleksandar – JEVTIĆ Petronije – JAIĆ Milan :::: THE IMPACT OF WOOD STAINING ON THE ADHESION OF CERTAIN TYPES OF COATING

111

17. 17. 17. 17. PERIĆ Ivana – GRLADINOVI Ć Tomislav – STARČEVIĆ Igor – STASIAK-BETLEJEWSKA Renata:::: ON ENHANCING OF PRODUCTION PLANNING IN WOOD PROCESSING AND FURNITURE MANUFACTURING

119

18. 18. 18. 18. SMARDZEWSKI Jerzy – MAJEWSKI Adam – PREKRAT Silvana :::: EFFECT OF CELL-WALL ANGLE ON THE UNIAXIAL CRUSHING BEHAVIOUR OF PAPER HEXAGONAL HONEYCOMBS

127

19. 19. 19. 19. STANKEVIK SHUMANSKA Mira – MELOSKA Živka – EFREMOVSKA Violeta :::: IMPACT OF THE ECONOMIC CRISIS ON THE WOOD INDUSTRY PRODUCTION IN REPUBLIC OF MACEDONIA

137

20. 20. 20. 20. STASIAK-BETLEJEWSKA Renata :::: CONSTRUCTIONS OF THE ENERGY-SAVING WOODEN HOUSES AND ITS ADVANTAGES ON THE EXAMPLE OF POLISH CONSTRUCTION

143

21. 21. 21. 21. SVOBODA Jaroslav – TAUBER Jiří:::: MICROCLIMATIC CONDITIONS FOR HEALTHY SLEEP AND REST – INFLUENCED BY SCIENCE, PSYCHOLOGY AND DESIGN

151

22. 22. 22. 22. ŠIMEK Milan – KO ŘENÝ Adam – DLAUHÝ Zdeněk – MIHAILOVI Ć Stefan:::: POSSIBILITIES OF CNC MANUFACTURING WITH REGARD TO FURNITURE DESIGN

157

23. 23. 23. 23. ŽUPČIĆ Ivica – GRBAC Ivica – BOGNER Andrija – ŽULJ Ivan – LJ ULJKA Boris: INFLUENCE OF MOISTURE CONTENT ON THE STRENGTH OF WELDED JOINTS

167

24. 24. 24. 24. YAPICI Fatih – ESEN Raşit :::: THE EFFECTS OF PRESS TIME AND PRESS PRESSURE ON MODULUS OF RUPTURE AND MODULUS OF ELASTICITY PROPERTIES OF ORIENTED STRENGTH BOARD (OSB) MANUFACTURED FROM POPLAR WOOD

175

25. 25. 25. 25. YORUR Huseyin – YAPICI Fatih – ESEN Rasit:::: THE EFFECTS OF CAST-POLYAMIDE ON THE MODULUS OF RUPTURE AND MODULUS ELASTICITY OF ORIENTED STRENGTH BOARD (OSB) MANUFACTURED FROM SCOTCH PINE

179

WOOD IS GOOD USER ORIENTED MATERIAL, TECHNOLOGY AND DESIGN

1

Klismos - The Style and Form of the Ancient Greek Chair

BARBOUTIS Ioannisa*– KAMPERIDOU Vasilikia a Aristotle University of Thessaloniki, Faculty of Forestry and Natural Environment, Laboratory of Wood

Products and Furniture Technology, Thessaloniki, Greece *Corresponding author: [email protected]

Abstract - The Greek furniture tended to be round, curved, ornamental, comfortable, supportive to the body and functional. The most characteristically Greek furniture form was the klismos chair. Prior the Greek klismos, chairs had hard stiff backs and arms, while klismos is a less extravagant piece of furniture, an elegant Greek chair with a curved backrest and legs. Characterized by grace and symmetry, klismos was essentially plain, with legs curving out from the seat and a back support consisting of a simple rectangular panel curved inward from sides to centre. The chair acquired a broad horizontal back slat at the top that encircled the shoulders of the seated person, establishing a fixed form of the classic chair. It offered a new type of support for the back than the straight back, or slanted back chairs of earlier times, while its light weight made it easily moveable. In this study the form and style of ancient Greek chair klismos are presented and analysed, the evolution of the architecture and designs of ancient Greek chair through the ages, while valuable information is also recorded about the methods, the materials and types of connection used in klismos construction.

ancient / chair / design / furniture / Greek / klismos 1. INTRODUCTION

As the years went by, primitive man having satisfied the basic needs and having solved some of his basic problems like food, clothing and shelter, he embarked on a synthetic task and manufacturing operation, in which raw materials were manufactured and transformed into useful objects, among them also furniture. He realized that the human body performs a serious task, probably that it is a living organism which gets tired and needs to rest, so he invented constructions for repose, which nowadays are called beds, chairs, stools, etc. In order to meet other human needs other kinds of furniture was created respectively, for example to store and deposit fruits and other goods such as shrines, lockers, banks etc. were created.

In the ancient Greek house there were no complex and multicomponent furniture. There were few pieces of furniture and among them there was the klismos, a chair that is well known for its harmony and beauty, since it erects from the floor with calm curves and results in deep elliptic back (SARIDIS, 1982). Klismos is an autonomous Greek creation that does not have its origins in Egyptian or Assyrian patterns, as with some other types of ancient Greek furniture like stools, tables, beds, etc. (RICHTER, 1959).

As it is known, in ancient Greece the son or daughter that was going to marry, was taking as dowry from the family home, among other things also furniture. Undoubtedly, among other things, the furniture in Ancient Greece was also a means of social promotion and demonstration object. Quite remarkable is the fact that the production of elegant furniture of best fit and quality was a source of enrichment for ancient cities or regions like Chios, Miletus and Thessaly. The Greek furniture tended to be round, curved, ornamental, comfortable, supportive to the body and functional. From the 6th century BC, already formed Greek furniture are presented, which are clearly of Greek inspiration, elaborate, full of grace and harmony, elegant and simple (SARIDIS, 1982).

The image of the excavation material in relation to the architecture of the Late Classical and Hellenistic houses indicates that the amount of furniture in homes is proportional to the house area, the availability of materials in the surrounding area, the cost and of course the time one spending in the house. The quantity of perishable furniture cannot be accessed, but


2

some assumptions could be made: wooden furniture was used widely in areas where wood is abundant (e.g., Macedonia), and possibly the construction did not require in all cases professional carpenters or joiners. The daily life did not necessarily require furniture in house, and there are iconographies that depict also dinners on the floor. Reports such as Menander declare that the furniture that we see most often depicted in the vessels were in homes of most privileged and was not the rule in all homes. The time of being inside the house was the other reason for not having too many furniture in the house. It is a fact that many household work takes place in the backyard or outdoors because of limited light in the house, which is the reason probably that they used furniture of easy transportation. Although some windows were found in Hellenistic Greece in Vergina Palace (houses of late Hellenistic Delos imitation windows on the grave of Lefkada) to name a few examples, large windows, bringing light into the house, appear only after the 1st century B.C. There is also vagueness about the placement of furniture in the house, which indicates that the areas of the house were not dedicated to a single occupation, like today. The practice of separating specific spaces as bedrooms, kitchens, bathrooms, living rooms, etc. belongs to the 18th century and even more in the 1930s. Therefore, the house in antiquity should be seen as a vague space where everything happens according to the time of the day, the climate, the mood of owners, dimensions of the room, the number of persons who are at home that time etc. (ANDRIANOU, 2009).

The necessity, usability and the main types of furniture did not changed materially from the ancient times to the present. Klismos was selected to be analysed and presented in this paper because it presents great interest from manufacturing point of view in relation to other types of furniture. From the existence of some klismos can be derived the metrology, their detailed dimensions and evidence of typological evolution, elements which help us in substantial study and conclusions about this seat. As often happens with archaeological data since the material remains of furniture of the houses are not enough to form a complete picture, researchers try to fill in the gaps, as far as possible, by combining findings from various geographic excavation places literary sources and iconography (ANDRIANOU, 2009). 2. HISTORY AND MORPHOLOGY OF KLISMOS

Generally, available material for information about the furniture of ancient Greece offer apart from the written tradition and the ancient monuments (sculptures, reliefs, vase paintings, frescoes, mosaics, coins, jewellery and stamps). The word klismos is a compound word with the first component «κλι-»(kli) coming from «κλίνειν» (klinin) which means recline and has a direct relation to the «κλίνη» (klini) (bed). The word klismos was basically used to describe the comfortable chairs with curved backrests and legs that are not thrones.

Klismos is presented only in sculpted works or reliefs, as well as, angiography. Paradoxical and difficult to interpret remains the facts that while other archaeological sources depicted innumerable forms of other types of furniture, klismos was not shown.

From the earliest Neolithic period (6000 - 5000 BC) the type of a seated male figure has already formed, as evidenced by the clay effigy of seated man from Pyraso of Thessaly, which sits majestically on the stool with his hands resting on the thighs and knees. Respectively, identical seats were found in many Neolithic settlements in Thessaly. The two curved legs stool illustrated in that effigy are constructed with curved branches and have a flat mounting for the man who is seated (ALEXIOU, 1992).

During the Bronze Age that follows (2800 - 1100 BC) several metals were widely used (copper, gold, silver), and therefore, more powerful, bronze tools were constructed and used. The general intellectual, cultural and tooling development and realization of anatomical needs, such as support and rest of the user's back seat contribute in the evolution of the seat in a seat bearing a backrest. The form of klismos probably came from the evolution of some type of seat of the geometric or archaic period (RICHTER, 1959).


3

A. B.

C.

Figure 1. A., B., C. Klismos illustrated in angiography

The addition of the backrest is an important innovation because it shows that cabinetmakers comprehend that the furniture is a "nest" or "embrace" or "template" that accepts man to sit down, work or rest. It is true that the seat without backrest (stool) still remains in use, just like today. Great importance held that the manufacturers were aware of the anatomy of movement and function of the human body (ergonomics - anthropometry), as evidenced by the proportions of a chair and the dent on the top surface of the seat for better hospitality of buttocks. Klismos has often integrated a footrest/footstool between the two front legs, in order to place the feet and rest them and it was mainly used by mortal people that are socially superiors. Usually, this small piece of furniture was separate from the furniture of klismos. In ancient literature the form of a klismos was not fully described as we know it from the ancient Greek artworks, possibly because Homer often refers to another Mycenaean chair that is tripod.

Klismos was being used by men and women of any age and post, equipping homes, workplaces, palaces, in which case apart from simple chair it functioned as throne. The basic construction material of klismos was wood, and there were more lavish klismoi made of gold, either solid gold or of gold leaves, or silver with ivory in the back of the chair. Often a chair was covered with precious fabrics and animal skins, which is illustrated also in pots or tombstones.

Klismos consists of two front outwards curved legs, which are wide at the top and narrow at the bottom. The two rear legs are also curved outwards and here there is a progressive reduction of the leg width from the height of the seat and downwards. The hind legs extend over the height of the seat, creating a curve inwards. Thus, the elongated upwardly hind leg has the shape of "S" with gentle curves. The front legs are connected with the hind ones at the height of the seat with four edge beams-transoms, with joints of mortise and tenon, pegs or dowels. In the upper part of the rear leg rests a curved plank, that nowadays is called "omitis", in order, on the one hand, the seated person to rest the shoulders and on the other hand, for structural, static purposes and support of the furniture. In the interval between the lower part


4

of "omitis" and the highest point of the rear beam-transom, there is a slightly curved plank, which now is called “label”, which supports the backbone of the seated person. The chair of klismos is usually austere; it does not bear a particular decoration, such as lion feet, heads of swans etc. nor transoms between the legs (ALEXIOU, 1992). Mainly in the first appeared klismoi, the backrest often bended backwards, where a head swan or a palmette overtopped. The morphology of klismos is based on specific set of curved elements, so it is easily recognizable furniture. Nevertheless there are variations in the heights, the dimensions of the “omiti”, the curvature of the legs etc. Frequently, we observe ancient Greek furniture that folds, such as folding stools, thrones etc., while klismos does not present this kind of folding design.

A. B.

Figure 2. A., B. Configuration of klismos with wide “omitis”

Klismos is mainly illustrated in pottery within everyday life scenes, which demonstrates that it was not used as a throne. It also stands out for its simple and rectangular form and it got its basic form elements from the throne. From mid 5th century BC when klismos started to be widely used, it replaced to some extent the use of throne. The stone klismos was destined for outdoor environment, whereas the wooden one for indoor use. Unfortunately no wooden klismos survived till our times, because through the years this wood has been found under the appropriate conditions for growth of decay fungi, which totally destroyed these furniture pieces. Wood was used dry by the craftsmen, since they had already known that wet wood causes checks, bending and distortions to the final structures. Furthermore, the ancient craftsmen used to dry out the wood naturally, covering it sometimes with manure, to protect it from the abrupt changes in weather conditions. In 475 BC, according to the ancient monuments of Greek art, the classic type of klismos was established, that specific type with the “omiti” which rests at the top of the rear legs (ALEXIOU, 1992).

Based on the illustrations of klismos and on the stone klismoi that were rescued, one could declare that the height of a klismos was 46 centimetres ±2. The acceptance of the height of existing stone chairs as a base for the metrology of such furniture is essential, since the depictions of klismos in other monuments such as vases, tombstones etc. do not reflect the real dimensions. Based on the dimensions of existing chairs, the proportions seem to create a sense of order and harmony among the elements of the chair synthesis. Thus, the imaginable rectangle with dimensions of 23x26 cm, in which the low backrest of a chair and the seat surface are two times smaller than that which the surface of the seat with the legs are included and has dimensions of 46x46 cm.

The unfussy morphology of the classic klismos, derived from all the curved elements that are comprised by, makes it undoubtedly one of the most beautiful creations in the field of furniture, combining relaxation with morphological simplicity and grace. Over the years, the shape of klismos evolves and the proportions are modified. Thus, the narrow “omitis” that


5

eminently dominated in the late Archaic and early Classical era, widens considerably during the Hellenistic era. The morphological relations between the seat, in relation to the other proportions of the furniture and the bowing of the legs etc. are all improved. Each piece of klismos is a unique chair and its construction is not precisely repeated, because it is difficult to achieve this, but also because of manufacturing specialties of klismos. Several attempts have been made to make a classification of klismos, based mainly on dimensions and proportions each one has. “Omitis” is characterized to be “narrow”, when it is narrower than the ½ of the height of the seat, regardless of the total height of klismos or the height of seat. Mainly during the late classical and Hellenistic era the wide “omitis” predominates. Typical example of a klismos with a narrow “omiti” is the famous chair, the klismos of Hegeso («Ηγησώ»), depicted in a relief on the famous Attic Tombstone and dates from the late 5th century BC. There are also klismoi with “omiti” of “equal size”, in which the “omitis” height is equal to the half of the seat height, regardless to the total height of a chair, the slope of the seat backrest or the legs curving. This type is established in 450 BC and does not appear often, but still appears till the Hellenistic era (ALEXIOU, 1992).

A. B.

Figure 3. A., B. Characteristic pictures of Ancient Greek klismos: A. in tombstone of Hegesus, B. tombstone found in Viotia (late 5th cent. BC)

In the klismos category with a back rest of “equal dimensions” belong the chairs, whose

backrest height is equal to the height of the seat. This type probably first appeared in the early 5th century BC and was repeated continuously on pottery, tombstones and votive columns up to the first fourth of the 4th century BC. In fact, in some klismoi also the depth of the seat corresponds and complies with these dimensions.

The most common type of klismos is that in which the backrest height is greater than the height of the seating surface. The very high backrest first appeared in the early types of klismos (around 520 BC), which had a decoration with swans heads, as has been mentioned earlier. The presence of this klismos type continues to appear until the end of the 1st century BC, as evidenced in tombstones, depictions on vases and the surviving stone chairs. Several times this klismos type presents narrow “omiti”, probably in order the harmony to be achieved in this klismos, which is considered the one of lower aesthetics (ALEXIOU, 1992). The backrest of a chair, regardless of its height, forms an angle to the seating surface, which differs from klismos to klismos. Klismos with a vertical backrest, where the seat back forms an angle of 90o to the seating surface is a relatively rare type of klismos and is found mainly in seats of prehistoric period. A seat of this kind makes the body form a right angle with thighs, an attitude that nowadays is considered to be not at all ergonomic for rest. It could be more suitable for occasional seating in dining rooms or in short time gatherings. During the


6

more suitable for occasional seating in dining rooms or in short time gatherings. During the Classical era this klismos type reappears after 475 BC and continues to be met until the mid-3rd century BC.

The klismos with canted backrest is one of the most popular used klismos. The backrest is inclined about 110o±5o, from the seating surface. Klismoi with canted backrest appear since the prehistoric era. This slope allows the relaxation and rest of the body, which is compounded even more when the slope of the seating surface is 5-7o upwards, even though the seating surface of klismos was usually completely horizontal. A rare type of klismos is that, in which the backrest forms an angle of about 130o±5o with the seating surface. This extreme slope of the backrest, which actually transforms the furniture into a cline, can offer the absolute rest, only under the basic condition that the seating surface is inclined 5 – 15o, in order the seated person to avoid sliding forwards. The specific type of klismos appeared only during the 5th century. The horizontal label is already found in klismoi of prehistoric era, when the prehistoric craftsmen quite wisely considered it necessary to have this item in the middle of the backrest to support the human backbone. Unfortunately, most of klismoi are laterally depicted on the monuments, so the presence of the label is not always visible. On the other hand, there is a small but sufficient number of klismoi represented on their front side or designed prospectively, as in seated statues, or in the surviving stone klismoi that can be substantiated both the existence and morphology of the label.

The curving of the legs, irrespectively of the height or the seating surface depth, corresponds to an arc of a circle or an ellipse, most of times. The curved legs of klismos of “Hegeso” are arc of ellipse with major axis of 39.5 cm and a minor axis of 25 cm. However, the chord of the arc of the front leg is longer (38 cm) than that of the rear leg (36.5 cm). The curved legs of that type of klismos are normal, since most of klismoi are found to have similar sizes and carvings, while only minor deviations have been detected. It is extremely rare the phenomenon klismos to obtain vertical legs. However, from 510 BC a klismos type appears which has vertical hind legs and curved front legs. This type of klismos still appears until the end of the 5th century BC, perhaps even later (ALEXIOU, 1992).

The surface of seating is created using several bands which are placed and fixed from one edge to the opposite, thus they often cross with each other, creating a comfortable seating surface. Careful observation of klismos illustrations on pottery revealed the following four different ways, in which the leather bands were tied in rows to create the seating surface of klismos: 1. in doubles, triples or hexads, which is the most usual way of tying the bands, 2. in series, which is quite common way 3. combination of the above tying ways with cross way, 4. only cross wisely. The last two ways are much complicated and therefore, are not so commonly used in tying the bands of the seating of klismos (ALEXIOU, 1992).

The curved wooden members of klismos were not manufactured by carving a bigger wooden element to smaller, but with other more advanced techniques. The technique of bending the board mechanically was widely applied in ancient Greece (evidenced by Theophrastus). The bending was implemented using steam or soaking the piece for a long period in amorgos-olive, a substance that was used by the ancients as therapeutic - demulcent substance, and also to soften skin and wood. Afterwards, the wood was placed in a special mould in order to achieve the desired shape. Another version for the manufacturing of curved wooden elements is the use of laminated timber technique, which was already known in ancient Egypt.

The use of curved legs imposed the use of very resistant to loadings forest species. Mainly hardwoods were selected (beech, oak, etc.) rather than softwoods (pine, fir, cypress, etc.). The hardwoods were more easily rubbed, polished, bent, while they are also more durable and dense wood species. Several adhesives were being used in klismos assembly and construction. Various glues of plant origin were used, such as starch paste, Arabic gomi, gluten, glue of Semolina and pollen or of animal origin, such as casein, glue coming from blood, collagen protein etc.


7

For the preservation of klismos or other furniture of those times, two types of protective substances must have been used. Firstly, substances applied on surface or varnishes that have little penetrating potential and create a very thin film on its surface. These substances were usually originated from vegetable and pathological or traumatic tree secretions, such as gum of acacia, the balsam, generally komeoresines, derived from coniferous trees etc. These substances, however, can be also of animal origin, such as beeswax or the white part of egg. Secondly, there were impregnating substances that were totally absorbed by the wood pores, such as animal fat, oil derived from the cedar pith and amorgos from olives (ALEXIOU, 1992). The tools used most frequently were the axe, the saw, the deception, the hammer and lathe. Besides the classical joints of wood, such as mortise and tenon, dowels etc., used in the construction of klismos, metal studs and adhesives were also used (RICHTER, 1959). The joints of wooden elements in a chair were hidden and covered wisely with precious wood or metals. The decoration of klismos could be accomplished by the same the klismos craftsman, but the elaborate decoration of luxurious klismoi certainly would be undertook by a chair specialist/ decorator (gold-plating, ivory craftsman, painter etc.) who knew the art of decorating these furniture. Frequent decorative element of Classical and Hellenistic periods klismos were glyphs (grooves) that were carved on the four corners of the front and rear legs, as in the klismos of “Hegeso”. As mentioned earlier, palmettes, heads of swans and spirals often adorned the ends of the backrest, while the label was often adorned with various representations, satyr’s pictures, grapes and other relief decorations. Klismos often displayed a decoration of paints or written representations, while part of the decoration could be also regarded the intonation or discoloration of a cheap wood, which after the appliance of paints and varnishes gives the impression of quite luxurious furniture.

3. CONCLUSIONS

During the Bronze Age (2800-1100 BC) a backrest was added to the plain stool and the first type of klismos started to appear and be formed, which is a seat of simple morphology and does not bear hand props. klismos is illustrated in numerous ancient Greek artworks from the Archaic, Classic and Hellenistic periods. Over the years, there has been recorded a rich typological evolution of klismos and while initially it was characterized by a rich and heavy ornamentation (archaic period), due to the fact that it was derived from a throne, then it was turned into a simple, attractive and comfortable seat (classical era). The major importance of klismos for people everyday life is proved, except for the ancient Greek literary sources, also by its frequent depiction on tombstones, which indeed indicates funerary luxury, which could be demonstrated only socially prominent and wealthy people. 4. REFERENCES ANDRIANOU, D. (2009): The Furniture and Furnishings of Ancient Greek Houses and Tombs. New

York: Cambridge UP, 2009. SARIDIS, Ε. (1982): The ancient Greek furniture. Archaiologia, Issue 2: pp. 65-67. ALEXIOU, P. (1992): The ancient Greek Klismos. Doctoral thesis dissertation. RICHTER, G. (1959): A handbook of Greek art. Phaidon Press Ltd., London.


9

Quality of the Wooden Products for Design and Equipping Educational Institutions

DOMLJAN Danijelaa*– VLAOVIĆ Zorana – ŽUPČIĆ Ivicaa – ŽIVKOVI Ć Vjekoslava

JIROUŠ-RAJKOVIĆ Vlatkaa – GRBAC Ivicaa a Department of Furniture and Wood Products, Faculty of Forestry, University of Zagreb, Zagreb, Croatia

*Corresponding author: [email protected]

Abstract – Equipping educational institutions with quality and contemporarily designed furniture and equipment is a serious problem in Croatia. There are many inconsistencies and the quality of furniture and equipment is rather low (e.g. dimensions, materials, etc.). All these problems are partially a consequence of inadequate technical descriptions and lack of quality attributed to the products in use, especially in cases where companies bid on public tenders. With the aim to improve the conditions for equipping educational institutions with furniture and equipment, a team of experts at the Department of furniture and wood products of the Faculty of Forestry in Zagreb published the Manual for Wood Products Quality for Educational Institutions in the framework of the project entitled Wood Is Good. The intention of the Manual is to stimulate and introduce high-quality furniture, equipment, construction products as well as other wooden products into the public procurement system, actively involve architects and designers in the production and motivate responsible methods for monitor and control production and delivery of wood products for equipping educational institutions. The authors believe that this document can serve as the platform for interdisciplinary analysis of various problems related to equipping educational institutions and preserving health of users.

furniture / educational institutions / equipment / design / technical description 1. INTRODUCTION

One of the most important problems noticed over a longer period of time in Croatia is primarily related to inconsistency and lower quality of products procured for the educational institutions along with inadequate materials used in production which prove to have harmful effects on health (DOMLJAN, 2011). The existing written documents about pre-school, primary and secondary education in most cases do not pay enough attention to quality of adequate furniture and equipment or other products needed in educational institutions for all activities related to the educational process and psycho-physical, cognitive and other needs of children and youth (PASALAR, 2003; HIGGINS et al., 2005; DUDEK, 2005; GRBAC – DOMLJAN, 2007; DOMLJAN, 2011; DOMLJAN – VLAOVIĆ, 2011). Aside from non-quality materials, problems often arise because of disproportioned dimensions of furniture in relation to end-users which can even result in health problems such as MSD/LBP (LINTON, 1994; KNIGHT – NOYES, 1999; PARACELLS et al., 1999; HAVIAROVA et al., 2001; WATSON et al., 2002; DOMLJAN, 2011). Producers hold certificates on the tested furniture quality proving that all precondition have been met and such documents are delivered in public procurement procedures but thus procured furniture very soon gets ruined and proves to be inadequate for users’ needs. The biggest problems result from non-observation of required descriptions contained in the technical specifications or inadequacy of technical descriptions lacking clarity and detailed elaboration. This results in self-willed interpretation on the behalf of incompetent investors who often do not consult experts. In many cases public procurement procedures for equipping educational institutions do not control the quality of procured products since they do not demand delivery of product samples or at least photographs showing the elements of an offer. The result is a wide range of products delivered for facilities that are rarely controlled in the final phase of the delivery and usually do not correspond with the basic standards of quality in respect of preservation of children and young people’s health (DOMLJAN – VLAOVIĆ, 2011).


10

1.1. Problem

Croatian educational system comprises pre-school, primary, secondary and high school education and institutions of higher education (***, 2012) and education takes place in facilities for a designated purpose such as kindergartens, schools or colleges. There are several documents clearly describing the procedures to be applied in equipping and defining the type and quantity of furniture for every room also stating information about how the interiors and exteriors of educational institutions should look like (AUF – FRANIĆ et al., 2003; AUF – FRANIĆ et al., 2004). From an architectural point of view, such interiors and exteriors in most cases have modern designs and responsible construction. However, the selection of furniture, equipment, flooring, doors, windows and other wood products used for interiors very often leaves this important segment for decision-making in hands of incompetent professions. Croatia lacks adequate and sufficient literature describing possible procedures for equipping educational and pedagogical facilities, defining quality, dimensions, requests and regulations for particular types of furniture, design and construction solutions as well as other details about how to equip educational facilities with quality furniture and wood equipment, floors, carpentry and other wood products (DOMLJAN, 2011; Case study for the 2002-2013 period). In general, the influence of products on the overall educational and pedagogical process and end-users is insufficiently taken into consideration. Over the past twenty years the Croatian educational system has introduced some important reforms that, among other things, intend to introduce co-working methods for learning and research. Unfortunately, those reforms have not changed the perception and design of furniture and equipment so that children work on old-fashioned, poorly designed furniture that does not correspond to functional and ergonomic requirements and use equipment that prevents them from participating in the new teaching and learning processes (DOMLJAN, 2009; DOMLJAN, 2011). This is mostly the case in primary and high school facilities and very often in kindergartens, too. All the above-mentioned factors indicate the most important problem conditioning the present situation where children and young people remain exposed to products that reflect negatively on their healthy development.

Aiming to improve the conditions for procuring furniture and equipment in educational institutions, the team of experts at the Department of furniture and wood products of the Faculty of Forestry, in Zagreb in the framework of the project entitled Wood Is Good and financed by the Croatian Chamber of Economy, Hrvatske šume d.o.o. and the Ministry of Agriculture, carried out the project named Publication of the wood products technical description book. The project took place from April 2012 to April 2013 and included cooperation between interdisciplinary experts from various fields such as medical science, ergonomics, economy, public procurement, wood constructions and technology, architecture, design and other. Field research, data collected from the existing documents and scientific research resulted in the Manual for Quality Preparation of Technical Descriptions for Wood Products Used in Educational Institutions.

This paper reflects on the Manual, its objective, aim and application.

1.2. Project purpose

The purpose of this Project is to stimulate the introduction of high-quality furniture, equipment, construction, products (doors, windows and floors) as well as other products made of wood and wooden materials in line with the HRN EN norms into the public procurement system and other procedures related to equipping kindergartens and primary and secondary schools in Croatia. This can be done by means of technical descriptions, recommendations, norms and specialized product descriptions for wood products and materials used for equipping educational facilities. Apart from the above-stated, the purpose is also to engage other professions, such as architects and designers, in the creation of wood products and stimulate responsible mechanisms for monitoring and controlling production process and


11

delivery of wood products used in equipping. Thus, all procedures related to decision-making, procuring and equipping necessarily have to involve not only investors and producers/suppliers of furniture and other wood products, but also other professionals such as architects, designers, constructors, quality experts, medical specialists, experts in ergonomics and other in order to improve product quality and competitiveness as well as to find a solution for the problem related to inconsistency noticed in the present procedures used for equipping educational facilities. The intention is also to stimulate the application of the new solutions (in terms of design, construction, technology and so on) for wood products founded in contemporary scientific research and expertise.

1.3. Project objective

The main objective of the Manual is to provide a framework for defining quality in technical descriptions for particular wood products that are most often used for equipping kindergartens and schools and which are defined in the existing regulations and documents on the national level. To be more precise, the main objective is to introduce a unified and comparative quality system for wood products that could be used by producers/suppliers in order to competitively participate in public procurement procedures for equipping educational facilities and improve the quality and better use of wood products. 2. RESULT OF THE PROJECT – THE MANUAL

Manual for Quality – Preparation of Technical Descriptions- Wood Products - Tome I – Educational Institutions is a result of the project named Publication of the wood products technical description book. It is composed of three main parts.

The FIRST PART is composed of chapters entitled About the manual, which contains some basic remarks and explains the purpose, objective and expected results of the Project, whereas the second chapter entitled Contemporary findings serves as an introduction in various problems linked to equipping educational facilities, lists all the existing documents in Croatia and analyses the results of scientific research in the field of contemporary educational processes, etc.

The SECOND PART represents the main part of the Manual and contains three chapters. The chapter An introduction to wood product quality describes general conditions and quality factors and provides explanations for some of the basic terms contained in the Glossary. This part of the Manual also gives recommendations for the norms applied in the field of furniture and furniture parts as well as characteristics for construction and other wood products. Next chapter Furniture and equipment lists the most important requirements and recommendations for designing furniture and equipment. These include specifications for technical quality, constructional and safety regulations, ergonomic and anthropometric factors, pedagogical and esthetical requirements, application of wood and non-wood materials, surface finishing, upholstering and other. The most important examples are given and described for various types of furniture used for storing, working and consuming food, sitting and lying together with equipment elements. Technical descriptions are also given for some of the typical examples for each particular type of furniture. The last chapter of the Second part Construction products also provide a list of requirements and recommendations and describe some exemplary prototypes in this category: doors, windows and wooden floors.

The THIRD PART and the chapter Visions and new proposals for equipping is intended for all types of users, i.e. children, young people, parents, teachers and others but mostly for those who participate in designing and equipping educational facilities or designing and producing furniture and equipment that will be used inside of such facilities. Follows Conclusion and References with more than 120 quotations.


12

3. QUALITY OF THE WOODEN PRODUCTS

The biggest problem in equipping facilities is quality of furniture and wooden products with their technical descriptions. If a particular technical description is incorrect and written unambiguously there is a possibility that investors, producers, procurers and other interested parties in the process of procuring and equipping educational institutions simply cannot understand the overall process.

Aiming to achieve a unified quality of technical descriptions for particular wood products that are most frequently used for equipping educational institutions, the Manual lists some of the basic elements of furniture and equipment whose typology is founded in the Croatian Pedagogical Standards (***2008a, ***2008b, ***2008c), together with expended variants for each type.

Wood products used for equipping educational institutions in most cases comprise furniture for sitting and working (chairs, armchairs, tables and other), furniture for lying (beds), furniture for storing (cabinets, shelves, glass cabinets and other), and construction products (doors, windows, wooden floors). The Manual contains more than one hundred wood products described as possible but not single solutions. Various specificities and characteristics are defined for each group (type) along with relevant explanations for individual product typology. Each individual product belonging to a particular type is presented spatially (sketch) and described in a way it contains dimensions, purpose, construction description, materials, processing, safety requirements and enforceable norms and product variants (if there are any).

The items for furniture description on example of school cabinet are given in Table 1.

3.1. Product description example

This chapter contains a simplified example of a product technical description for a school cabinet together with main defining categories (Table 1).

Table 1. Items for furniture description (e.g. cabinet)

TECHNICAL DESCRIPTION:

PRODUCT NAME: PRODUCT USE AND BRIEF DESCRIPTION: DESIGN AND QUALITY STANDARD: FUNCTIONAL (OVERALL) DIMENSIONS: COMPOSED (w×l×h) / PACKED TYPE AND QUALITY OF WOOD MATERIALS: TYPE AND QUALITY OF NON-WOOD MATERIALS: PROCESSING ACCURACY (FINESS) OBRADE: CONSTRUCTIONS AND ASSEMBLING: SURFACE PROCESSING: PACKAGING:

4. CONCLUSION

Interiors used for education are not generic. Each new project should take into consideration time, place and users as well as dimension of children and young people’s healthy development. The entire process should be rational, responsible and defined by norms, which does not presuppose their inflexibility. Thus, the Manual does not define single solutions and designs but rather provides a set of recommendations, requirements and research data for use in the production of quality wood products offering various possibilities for design and further development and research.


13

Furniture and equipment are by no means the most important elements of educational process but they strongly influence its methods and overall quality. Sometimes furniture and equipment play a decisive role in motivating or discouraging students from learning and participating in school work and protecting their health together with other factors listed in the Manual. The authors believe that further research in the field should take that direction.

Present research indicates that most of attention, energy and resources were invested in analysing working environments mostly used as offices and problems encountered by the working population sitting in offices. Now is the time to reconsider healthy development of

children and young people in educational institutions where comfort, motivation, communication and well-being play the most important role. New programmes, technologies and working processes in all segments of educational system require changes. It is up to as, as socially responsible beings, to stimulate, adopt and apply such changes for the well-being of the youngest population and the society as a whole.

The Manual presented in this Paper is, hopefully, a contribution to such intentions.

5. REFERENCES AUF-FRANIĆ, H.; OLUIĆ, V.; ŽARNIĆ, T.; BERTINA, M.; KORLAET, L.; RISTER, V.; ROTH-ČERINA, M.

(2003): Nurseries and kindergartens – guidelines for programming, planning and designing. (in croatian) University of Zagreb - Faculty of Architecture, Zagreb, acta architectonica.

AUF-FRANIĆ, H.; OLUIĆ, V.; ŽARNIĆ, T.; BERTINA, M.; KORLAET, L.; RISTER, V.; ROTH-ČERINA, M. (2004): Primary schools. Programming. Planning and designing. (in Croatian) Golden marketing, Tehnička knjiga, University of Zagreb - Faculty of Architecture, Zagreb.

DOMLJAN, D. (2011): Designing school furniture as a precondition for preserving pupils’ health. (in Croatian) Doctoral thesis. University of Zagreb, Faculty of Forestry, Zagreb.

DOMLJAN, D.; VLAOVIĆ, Z. (2011): Technical documentation for equipping kindergartens, Project: Introducing standardized equipment and furniture in the pre-school educational system. (in Croatian) University of Zagreb - Faculty of Forestry.

DUDEK, M. (2005): Children Spaces. Architectural Press, An imprint of Elsevier, Oxford, Burlington, UK.

GRBAC, I.; DOMLJAN, D. (2007): Furniture for a healthy life, Sigurnost 49 (3): pp. 263-279. HAVIAROVA , E.; ECKELMAN , C.; ERDIL, Y. (2001): Design and Testing of Environmentally Friendly

Wood School Chairs for Developing Countries. Forest Products Journal 51 (3): pp. 56-64. HIGGINS, S.; HALL , E.; WALL , K.; WOOLNER, P.; MCCAUGHEY, C. (2005): The Impact of School

Environments: A literature review. Design Council. The Centre for Learning and Teaching. School of Education, Communication and Language Science, University of Newcastle, UK. URL: http://www.cfbt.com/PDF/91085.pdf

KNIGHT, G.; NOYES, J. (1999): Children’s behaviour and the design of school furniture. Ergonomics 42 (5): pp. 747-760.

LINTON, S.J.; HELLSING, A.L.; HALME , T.; ÅKERSTEDT, K. (1994): The effects of ergonomically designed furniture on pupils’ attitudes, symptoms and behaviour. Applied Ergonomics 25 (5): pp. 299-304.

PARACELLS, C.; STOMMEL, M.; HUBBARD, R.P. (1999): Mismatch of classroom furniture and student body dimensions. Empirical findings and health implications. Journal of Adolescent Health 24 (4): pp. 265-273.

PASALAR, C. (2003): The effects of spatial layouts on students' interactions in middle schools: multiple case analysis. Doctoral dissertation, Faculty of North Carolina State University, USA.

WATSON, K.D.; PAPAGEORGIOU, A.C.; JONES, G.T.; TAYLOR, S.; SYMMONS, D.P.M.; SILMAN , A.J.; MACFARLANE, G.J. (2002): Low back pain in schoolchildren: occurrence and characteristics. Pain, 97, pp. 87-92.

*** (2008)A: National pedagogical standard for pre-school education, Croatian Parliament, 16 May 2008. URL: http://narodne-novine.nn.hr/clanci/sluzbeni/2008_06_63_2128.html

*** (2008)B: National pedagogical standard for elementary school education, Croatian Parliament, 16 May 2008. URL: http://narodnenovine.nn.hr/clanci/sluzbeni/2008_06 63 2129.html


14

*** (2008)C: National pedagogical standard for high school education RH, Croatian Parliament, 16 May 2008, URL: http://narodne-novine.nn.hr/clanci/sluzbeni/339619.html

*** (2008)D:. HRN EN 1729-1: Furniture – Desk and chairs for educational institutions – 1st part: Functional dimensions (EN 1729-1:2006), HZN Zagreb, CEN Brussels.


15

The Effects of Press Time and Press Pressure on the Screw Strength Properties of Oriented Strength Board (OSB) Manufactured from Poplar

Wood

ESEN Raşita*– YAPICI Fatihb a Karabük University-Technical Education Faculty- Department of Furniture and Decoration Education Karabuk

and Turkey b Karabük University- Forestry Faculty- Department of Forest Industry Engineering Karabuk and Turkey

*Corresponding author: [email protected] Abstract – The effects of press time and press pressure on the screw strength properties of oriented strength board was investigated. For this purpose, 80mm long strands made of Poplar were bonded with phenol-formaldehyde resin at (9 %) with three-layer cross-aligned OSBs. The strands used for the production of test panels were made up 50 % of core layer and 50 % of outer layers. The panels were pressed for three different press times (3, 6 to 9 minutes), under 30, 40, and 50 kg/cm2 bar pressure, aiming for a target density of 0.67 g/cm3. It was observed that the screw strength values were changed between 637-945 N.

oriented strand board / phenol-formaldehyde / screw strength / mechanical properties 1. INTRODUCTION

Oriented Strand Board (OSB) is an engineered structural wood panel. OSB is made by processing small diameter, fast growing trees into thin strands which are bonded together under heat and pressure with an exterior resin binder. OSB panels are used various applications such as building construction, furniture, roofing and flooring.OSB parts join with nut, nail, and screw at using area (YAPICI et al., 2009).

In a previous study on OSB, wooden composite materials which are to contain panel products such as medium-density fiberboard,particleboard, plywood, and (OSB). Besides, the diminished supplies of larger dimension timbers have created high pricing (HU, 2000; GRIGORIU, 2000). OSB has been found to have mechanical properties equal to those of plywood for structure and to be manufactured comparatively cheaply (BROCHMANN et al., 2004). It was reported that an increase of coment-wood ratio resulted in increase of all but MOR values of OSB (ANTONIOS et al., 2006).

There are many important factors which affect physical and mechanical properties of wood composite materials (GALBRAITH , 1986).When OSB roof or wall sheathing is exposed to environmental moisture, it is degraded (BROCHMANN et al. 2004).

Researchers have studied the screw strength properties of wood composite materials by using various processing variables. It is well known that the resistance of a nail or screw shank to direct withdrawal from wood based materials is a function of several factors, including nail diameter, and depth of penetration (FPL, 1999). It was reported that demountable joints were more successful than stable joint in “T” joints used for the production of frame construction furniture (IMIRZI , 2000).

In another study, since the middle layer structure of the particleboard embeds the screw body, both mentioned parameters are considered important in the aspect of the quality of the edge screw holding performance. In order to have further insight into the conformation of the middle layer, the image survey was obtained on the split board section presenting the surface of the middle layer (MILJKOVIĆ et al., 2007).

YAPICI et al. (2009) stated that as the increase of adhesive ratio, pres time and pres pressure, which were used to production of the oriented strength board, the nail withdrawal


16

strength increases. They also, reported that the nail withdrawal strength values were changed between 124.60 and 334.81 N.

The production conditions of OSB panels are effective on mechanical and physical properties of OSB. The most important parameters affecting the properties of OSB are press pressure and pressing time. In this study, the aim is to evaluate the effects of press time and press pressure on screw strength of OSB. 2. MATERIAL AND METHODS

Mature Poplar wood was used in the production of the (OSB). The strands dimension in

usage was approximately 80 mm long, 20 mm wide and 0.7 mm thick. Firstly, the wood strands were dried until 3 % moisture content before adhesive was sprayed on them for three minutes. Then, the adhesive material within 47 % liquid phenol- formaldehyde resin, was applied in 9 percent ratios based on the weight of oven dry wood strands.

The press periods and press pressure were 3, 6 and 9 minutes under the 30-40 and 50 kg/cm2 press pressure, respectively. The shelling ratio was 50 % for core layer and 50 % for face layer, and density of the boards was aimed at 0.67 g/cm3 density. OSB panels, which were dimensioned as 56x56x1.2 cm were made for experiments, in the nine conditions. They were 18 in total as two for each. Hand formed mats were pressed in a hydraulic press. These panels were labeled from 1 to 6. All mats were pressed under automatically controlled conditions at 195±2 ºC. After pressing, the boards were conditioned to constant weight at 65±5 % relative humidity and at a temperature of 20±2 ºC until they reached stable weight (TS 642 1997). The density, moisture content, modulus of rupture and modulus of elasticity values of OSBs were determined according to the related standards (TS-EN 323 1999; TS-EN 322 1999; TS EN 310 1999).

During the measurement of screw strength values were determined using Zwick/Roell Z050 universal test device with capacity of 5000 kg and measurement capability of 0.01Newton in accuracy. In testing, loading mechanism was operated with a velocity of 10 mm/min. Data for each test was statistically analyzed. The analysis of variance (ANOVA) was used (α<0.05) for testing significant difference between factors. When the ANOVA indicated a significant difference among factors, the compared values were evaluated with the Duncan test to identify which groups were significantly different from other groups.

3. RESULT, DISCUSSION AND CONCLUSION The density (D) and moisture content (MC) values of OSBs were determined according

to the related standards. The average density and moisture content of panels were obtained as 0.67 g/cm3 and 7.4 %, respectively. It was seen that the aimed and acquired D and MC values within the ranges specified in the related standards. The average and standard deviation of the values of the screw strength of produced panels are shown in Table 1.


17

Table 1. Summary of the test results of the OSBs

Screw Strength (N) Press Pressure (kg/cm2 )

Press Pressure (Minute)

Mean Std. Deviation

30 3 735,86 45,10 6 1.006,24 83,81 9 1.093,43 31,82

40 3 453,75 39,40 6 892,36 126,44 9 842,35 112,42

50 3 722,75 92,04 6 613,09 35,62 9 823,36 228,60

It was found that the screw strength values of the test panels varied between 453.75 and

1093.43 N. The lowest value for screw strength of produced panels was 453.75 N (40 kg/cm2 and 3 minutes press time). The variance analysis of screw strength based on manufacturing circumstances of test panels was done by using multi variance analysis (Table 2).

Table 2. The result of variance analysis

Screw Strength (N/mm2)

Source Type III Sum of

Squares Df Mean Square F-Value

Sig.Level (p<0.5)

Corrected Model 1521914,64(a) 8,00 190239,33 16,74 0,00 Intercept 28665980,28 1,00 28665980,28 2523,05 0,00 Press pressure 487212,75 2,00 243606,37 21,44 0,00 Press time 631928,70 2,00 315964,35 27,81 0,00 Press press. *press time

402773,20 4,00 100693,30 8,86 0,00

Error 409018,20 36,00 11361,62

Total 30596913,12 45,00

According to the variance analysis, the effects of the both press time and press pressure

on the modulus of elasticity values were significant statistically. Duncan test results conducted to determine the importance of the differences between the groups are given in Table 3.

Table 3. Duncan test Results

Application Type Screw Strength (N)

Mean HG

Press Pressure (kg/cm2 )

50 719,73 A 40 729,49 A 30 945,18 B

Press Pressure (Minute)

3 637,45 A 6 837,23 B 9 919,71 C

It can say that screw strength values changed between 637 and 945 N according to

Duncan’s test. Some homogenous groups were given the same column. It was seen that screw strength values were affected by changing press time and press pressure.

In this study, the values of screw strength which were among the most important mechanical features of oriented strand boards were determined according to related standard. Especially, it can be stated that as the press time increased, the screw strength of test panels


18

improved at the both press pressures. Although the highest screw strength related to 945.18 N was obtained from experimental samples by applying 30 kg/cm2 press pressure, the lowest screw strength of value related to 637.45 N was obtained from samples by applying 3 minute press pressure time.

4. REFERENCES BROCHMANN, J.; EDWARDSON, C.; SHMULSKY , R. (2004): Influence of resin type and flake thickness

on properties of OSB. Forest Prod. J. 54 (3): pp. 51–55. FPL, (1999): Wood Handbook-Wood as an Engineering Material. Gen. Tech. Rep. FPL-GTR 113,

Madison, WI, Department of Agriculture, Forest Service, Forest Products Laboratory, 463 pp. GRIGORIOU, H.A. (2000): Straw-Wood Composites Bonded With Various Adhesive Systems. Wood

Science And Technology 34, pp. 355-365. İMIRZI , Ö.H. (2000): Mechanical Properties Of Massive Furniture “T” Joints With Frame

Construction. M.Sc. Thesis, Gazi University Institute of Science And Technology, Ankara. MILJKOVIĆ, J.; POPOVIĆ, M.; MOMČILOVIĆ, D.M.; GRMUŠA, G.I. (2007): Edge Screw Withdrawal

Resistance In Conventional Particleboard And Osb - Influence Of The Particles Type. ГЛАСНИК ШУМАРСКОГ ФАКУЛТЕТА, БЕОГРАД BIBLIB: 0353-4537 95, pp. 109-117.

PAO-JEN, (STEVE) H. (2000): Bending Stiffness Prediction For Oriented Strandboard By Classical Lamination Theory, University of Toronto, 1-2.

PAPADOPOULOS, A.N.; NTALOS, G.A.; KAKARAS, I. (2006): Mechanical and physical properties of cement-bonded OSB. Holz als Roh- und Werkstoff 64 (6): pp. 517–518.

TS 642/ISO 554 (1997): Standart atmospheres and /or testing; Specifications TS-EN 323 (1999): Wood-Based panels,-Determination of density, TSE, Ankara. TS-EN 322 (1999): Wood-Based panels,-Determination of moisture content, TSE, Ankara TS EN 310 (1999: Wood-Based panels-Determination of modulus of elasticity and of bending strength,

TSE, Ankara. YAPICI, F.; GÜNDÜZ, G.; ÖZÇIFÇI, A.; LIKOS, E. (2009): Prediction of Screw and Nail Withdrawal

Strength on OSB (Oriented Strand Board) Panels With Fuzzy Classifier. Technology, 12 (3): pp. 167-174.


19

Analysis of User Preferences concerning e-trend in Kitchen Furniture Design

FABISIAK Beataa*– KŁOS Roberta – MAĆKOWIAK Katarzynaa

a Department of Furniture Design, Faculty of Wood Technology, Poznan University of Life Sciences, Poznan, Poland


Abstract – The aim of the study was to collect information concerning evaluation of requirements for furniture design created in e-trend. An additional practical objective was to propose examples of selected concepts of kitchen furniture representing discussed trend. Based on the questionnaire studies and direct interviews the data concerning lifestyle and using of new technology devices by users aged 40-60 and over 60 were gathered in order to identify the demand and need for providing furniture meeting the requirements of e-trend way of living. The results of the comprehensive statistical analysis performed on the collected data were presented, being the basis for creation of furniture concepts for kitchen. The selected solutions of kitchen furniture design representing e-trend and aiming at increasing the comfort of living were described.

design / kitchen furniture / e-trend in furniture design 1. INTRODUCTION

In consistence with the considerable technical progress in recent decades and the related change in consumers’ lifestyles, the perception of domestic space has also been modified. Designers have to follow these changes and respond to them adequately, creating products potentially most effectively meeting the needs of contemporary consumers. In view of the above the e-trend has been established in interior design, consisting in the implementation of state-of-the-art communication technologies in traditional furniture and furnishings. Application of such solutions in the kitchen space makes it possible e.g. to facilitate and shorten the time required to prepare meals or to provide meals adequate for the diet of a given user. When analysing the environment in which IT and communication technologies are used it need to be remembered that the information and social space are formed by interdependent networks of computers, devices and electronic media (PALCZEWSKA et al., 2011). Thus a characteristic feature for e-trend kitchens will be connected with the virtual digital space, facilitating for the room e.g. remote control over household appliances, communicators or interactive surfaces. Moreover, this will provide constant access to the Internet, which according to forecasts will become a window to the world, particularly for the elderly, thus improving their quality of life in terms of e.g. professional career, interests or social contacts, up to being completely independent (BATORSKI, 2010; BRADLEY – POPPEN, 2003).

In the future not only the kitchens, but also the entire living spaces will be transformed. Flats will be changed into multifunctional spaces combining four basic fields of life connected with the public sphere, home, work and leisure. The above mentioned spheres will overlap thanks to the development of new technologies, products and services, which will meet and satisfy the dreams, wishes and perceptions of users (JĘDRZEJCZAK – SPRYCHA, 2011). These actions will be reflected in flats in the future. Thus the bedroom will be combined with the bathroom, to be used for toilet, yoga, fitness, meditation and sleep, becoming a kind of an oasis for physical and emotional health (SKALSKA , 2010; WANNINGER, 2009). Taking into account the kitchen space it will be as compact as the bedroom and thanks to the new Air Purifying technology (removal of aroma particles from it) it may be combined with the living room. The same space will become the place to prepare meals, to work and to meet friends


20

(QUINN, 2011; EDELKOORT, 2011). The kitchen space will thus considerably gain in importance in comparison to its current status.

Most studies on the subject focus on the development of innovative devices used in the kitchen, i.e. economical dish-washers, ovens indicating when a given dish is ready or fridges monitoring the amounts and expiry dates of stored products (KRISHNAMOORTHY, 2001). Many projects aiming at the application of computer technologies in the kitchen have focused on the development of applications dedicated to e.g. interactive cook books or manuals establishing the most nutritious menu (KRISHNAMOORTHY, 2001).

Taking the above into consideration the aim of the study was to collect information concerning evaluation of requirements for furniture design created in e-trend. An additional practical objective was to propose examples of selected concepts of kitchen furniture representing discussed trend.

2. MATERIAL AND METHODS

It was decided to divide the methodology into two stages. The first stage will consist in conducting surveys and direct interviews in a group of 300 respondents aged over 40 years. Due to the assumed futuristic character of the planned kitchen and the application of state-of-the-art technologies in the project design it was decided for the share of respondents aged 40 - 60 years in the analysed population to be over 50 %. In the second stage the design assumptions will be formulated and the concept for the furniture and interior design in the e-trend will be established.

The survey questionnaire will consist of closed, open and semi-open questions. The subject will cover problems concerning the use of computer tools by the users in the analysed age group, activities performed in the kitchen and their preferences concerning the kitchen of the future.

Collected data will be coded and next subjected to a comprehensive statistical analysis using STATISTICA 10.0. Results of the investigations will constitute the basis for the development and proposals of new solutions for kitchen furniture created in the e-trend, which will potentially enhance the comfort of living of future users. They will be created using the Google SketchUp. The final design of kitchen furniture will be presented using the V-ray rendering programme.

3. RESULTS AND DISCUSSION 3.1. Results and discussion of survey research

In view of the percentage of returned questionnaires, the degree of their completeness and the number of direct interviews the direct statistical analysis was conducted on data coming from 281 respondents. The shares of individual age groups in the analysed population are presented in Figure 1. Women accounted for 63 % respondents and predominated quantitatively in each analysed age group.


21

Figure 1. The structure of the analysed group of respondents in terms of age and sex

Source: Own elaboration based on performed investigations

When designing furniture in the e-trend it is crucial to collect information on the computer and Internet skills of the users in the analysed age groups. Results of conducted analyses show that - as it could have been expected - the highest percentage of computer users is found for individuals aged 40 - 50 years (84 %). However, a 38 % group of respondents aged 61 - 70 using computers also need to be considered (Figure 2).

Figure 2. The structure of the analysed group of respondents in terms of age and computer skills

Source: Own elaboration based on performed investigations

A relationship was shown between white-collar work and computer skills. As many as 90 % individuals performing white-collar work in the period of their professional activity have computer skills. The analysed values are different in the case of individuals performing manual jobs, among which it is true in case of 55 % respondents.

It needs to be stressed that among individuals using computers most (from 88 % in the case of individuals aged 60 - 70 years up to 96 % users aged 40 - 50) also use the Internet.


22

What is interesting, such a situation is found in all analysed age groups (Figure 3). An increasing number of individuals aged 50+ uses the Internet, which indicates changes occurring among Polish 50-year olds (KRZYŻANOWSKA – DANIELEWICZ, 2010). According to the forecasts for the year 2030 these values will increase considerably, e.g. due to the fashion in highly developed countries and the EU initiative aiming at the creation of integrated digital society (EC COMISSION, 2007).

Figure 3. The structure of the analysed group of respondents in terms of age and Internet use

Source: Own elaboration based on performed investigations The need to include issues connected with new information and communication

technologies in the futuristic furniture design and interior design is also indicated by the analysis of the frequency of Internet use. In the group of respondents aged 40 - 50 years and 51 - 60 years among Internet users 44 % respondents log in to the Internet several times a day, while in the oldest analysed group this percentage drops to 40 % (Figure 4).

In the conducted analyses it was also decided to collect information on the usage of touch-screen operated devices. It was shown that 56 % respondents aged 40-50 years and as little as 14 % respondents aged 61 - 70 use such a mode of operation. This confirms the fact that with age problems appear in the operation of touch-controlled surfaces, connected with limited manual capacity of the elderly. Among respondents using such solutions household appliances ranked second after mobile phones as the most frequently touch-screen operated products.

Figure 4. The structure of the analysed group of respondents in terms of age and Internet use

frequency Source: Own elaboration based on performed investigations


23

When analysing consumer preferences concerning the e-trend in kitchen furniture design the application of modern solutions facilitating the use of different internet applications for foodstuff purchases, analyses of calorie content of individual dishes or operation of electrical appliances need to be taken into consideration. It was decided in this study to verify the level of respondents’ interest in on-line purchases of foodstuffs. Results showed that most respondents are not interested in this service (68 %). It is of interest that this group includes also individuals using the Internet at present (Figure 5). However, it is not connected with a lack of belief in the applicability of Internet solutions in shopping, but first of all a lack of confidence in the quality of food products offered in Internet shops.

Direct interviews indicated a lack of trust in the quality of thus purchased products among the individuals not interested in on-line shopping of foodstuffs. They showed distrust in relation to retailers. It turned out that the respondents prefer personal choices offering a chance for personal and direct evaluation of quality of a given product and the whole offered range of products. Results indicate a present-day lack of popularity of the described service in Poland, which will obviously change in the future. From year to year an increasing interest in on-line shopping among Poles in relation to products, which so far have not been treated by many consumers as typical on-line purchase options, e.g. food products may be observed (FRONTCZAK, 2012). The other respondents consider this offer to be interesting, among which 26 % surveyed individuals at present use the above mentioned service and 6 % would like to start using this option.

Figure 5. Interest of respondents in on-line shopping

Source: Own elaboration

Modern information and communication technologies are becoming a window to the world for contemporary users, providing extensive opportunities to follow the press and the news, listen to music, watch TV or talk or conduct video-conferences with the family, friends and colleagues. In view of the fact that the kitchen has always been and according to forecasts will continue to be the centre of the entire house, its design and furnishings should provide it with a multifunctional character and make it a multimedia centre. The need to create space with such properties is indicated by the results of an analysis of activities performed by the respondents when staying in the kitchen. The tasks most frequently performed in the kitchen, next to the traditional tasks connected with meal preparation (94 %) and consumption (75 %), should also include listening to the radio, reading newspapers and playing with children/grandchildren. Respondents also mentioned such activities as watching TV or using the computer. It needs to be stressed that among computer users in the kitchen as many as 60 % were individuals aged 40-50 years. Thus it may be expected that with an increasing popularity of IT solutions among the younger generations of users the use of computers also in the kitchen space will be increasing. The justification for the future transformation of the kitchen space into a multifunctional room is also indicated by results of studies showing that


24

51 % respondents aged 40-50 years would like to combine the kitchen with the dining room, the living room or another room.

An important stage in the analysis of user preferences was connected with the collection of information concerning the number of respondents willing to use the kitchen equipped with modern solutions aiding work in the kitchen, including Internet access. The study showed that as many as 60 % respondents were willing to buy kitchen furniture designed in the e-trend.

A combination of entertainment, social life and gathering information with basic activities performed in the kitchen provides the kitchen space with multifunctionality and confirms the justification for the commonly assumed thesis that it is the heart of each house. Among trend watchers these activities will not cease and will continue to increase in importance. It is even possible to move the office to the kitchen space (WANNINGER, 2009).

3.2. Selected solutions of e-trend kitchen furniture design

Analysis of housing needs indicates that in contemporary interiors objects combining more than one utility function are considered increasingly more desirable. In the future multifunctional products will gain in importance to an unprecedented degree (SKALSKA , 2010; EDELKOORT, 2011). According to SMARDZEWSKI (2008), a multifunctional piece of furniture in contemporary design has gain a new role and new quality, among other things thanks to its being saturated with electronics and automation, which significantly improves quality, comfort and safety of its use. Moreover, when presented in modern proportions and design – in contrast to previous periods – it is associated with luxury and safety. Designing of multifunctional concepts for kitchen furniture, with strongly integrated and interdependent functions, has made it possible to apply state-of-the-art technologies characteristic of the type of the designed e-kitchen.

In relation to the adopted design assumptions a concept of the e-kitchen was established, within the framework of which original and functional kitchen furniture was designed. In an ergonomic and intelligent manner it combines several functions, at the same time constituting a framework case for household appliances and modern technological solutions. The design project incorporates two types of furniture, a cabinet and a kitchen island, which due to its controlling functions and household appliances may be considered the centre of the designed kitchen. Moreover, the island is a centre for three mobile kitchen islands which may be assembled on its basis, which facilitates the creation of arbitrary arrangements of kitchen layouts (Figure 6).

Figure 6. Visualisation of the concept of designed kitchen furniture with separate islands



25

An important step in the design project was to develop kitchen furniture, which arrangement would provide the kitchen space the potential for a sterile workplace, in which all tools would be within easy reach, at the same time providing no obstacle for the smooth realisation of the user’s tasks. For this purpose a hexagonal shape of the kitchen island was divided into three identical rhomboid kitchen islands, thanks to which it would be possible to isolate three basic working areas in the kitchen, such as the washing area, the product processing area and the thermal processing area (Figure 7).

Providing dynamics to kitchen furniture thanks to the mobility of the islands, apart from the possibility to create an ergonomic work triangle, makes it possible for users to adopt any given utility area arrangement in the kitchen. This assumption makes it possible to offer various arrangements in the kitchen, including space for communal cooking with invited guests with the possibility to divide it into individual zones, a playground for children or space for exercise.

While attributing functions to individual islands it was decided to follow opinions of the respondents concerning the preferred type of lower cabinets and household appliances. In view of the fact that a vast majority of respondents (61 %) aged 40-60 years would like to have lower cabinets with drawers and some mentioned drawers as the missing piece of kitchen furnishings, it was decided to install them in all designed islands.

Figure 7. Visualisation of the concept for the island divided into 3 working areas Source: Own elaboration

In the modern world state-of-the-art solutions are frequently connected with the

elimination of furniture handles or buttons in household appliances, being replaced by touch panels to control the appliance mechanisms. A popular solution is to apply a touch system opening drawers in the kitchen space. In view of the results it was observed that the above mentioned solutions are used by as many as 51 % analysed group of individuals aged 40-60 years. For this reason it was decided to apply them in the proposed solution.

It needs to be mentioned here that a concept for the design of the e-kitchen in the form of kitchen cabinets composed of five zones: a fridge, a mini-conservatory and a specially arranged storage space for vegetables, fruits or dishes (Figure 8). It offers a possibility to arbitrarily arrange storage zones and enlarge them depending on consumers’ needs. An additional function is connected with lighting under the cabinet segments, which previously selected and coded colour would identify individual zones for product storage, in a simple manner signalling the cabinet contents to the user.


26

Figure 8. Functionality of the concept for kitchen cabinet


Based on information of users’ preferences obtained during direct interviews it was decided to design this innovative kitchen cabinet in the form of a traditional showcase. The visibility of the cabinet contents may be limited or completely obscured thanks to the interactive fronts. Moreover, an additional task for the interactive fronts would be to provide multifunctionality of the kitchen space. It may be concluded from the results of the survey that in modern households the users, apart from the performance of basic activities in the kitchen, are also involved in leisure activities. When selecting functions which would be assigned to the kitchen space the results of the questionnaire survey, showing that respondents most frequently listen to the radio, watch TV and read newspapers in the kitchen were taken into consideration. The above mentioned functions are served by the tablet mounted in the kitchen island, which through the digital environment makes possible videoconferencing with family and friends, medical consultations with doctors or physiotherapists in combination with exercise. Moreover, entertainment will be provided in the form of films, music and access to the latest news thanks to such media as television or radio. Moreover, the tablet mounted in the working surface will make it possible to switch images to a larger screen found in the pre-selected fronts of kitchen cabinets. The most important applications which were used in the designed kitchen concern first of all the field of health care, they facilitate consultations with doctors with no need to leave the house and the most advanced will take blood pressure measurements and measure blood sugar levels. These solutions due to the increasing costs of medical care will be valuable and commonly applied in the future. Other solutions affecting health protection are applications connected with maintenance of physical activity using a specially prepared exercise programme. The concept of the design also includes basic applications expected in the kitchen, related with recipes and required products, i.e. The photo cookbook - Quick&Easy. This e-cook book in a comprehensive manner, using photographs, presents individual stages of dish preparation shown by an experienced cook. 4. SUMMARY

Interest of respondents in the introduction of modern solutions in the kitchen space, its mechanisation and computerisation, ensuring user safety, functionality, easy performance of kitchen tasks and maintenance of cleanliness confirm the advisability of the developed concept of the e-kitchen. It results from these investigations that the proportions of computer and Internet users increase in the following groups aged 61-70, 51-60 and 40-50 years. Thus it needs to be expected that this trend will be maintained in the next years in accordance with


27

the growing popularity of IT solutions among young generations in highly developed countries.

Collected survey results and evaluation of the design phase by the users made it possible to design the kitchen of the future, perfectly matching the e-trend. Taking into consideration users’ preferences made it possible to develop a concept corresponding aesthetic preferences of the analysed group of users and furniture fittings with modern IT solutions improving the standard of life.

The study focused on the application of state-of-the-art IT and communication technologies in the design, thus incorporating the latest design trends in this project. A design of ergonomic, functional and original kitchen furniture was created, facilitating development of social interactions, motivating to be active and increasing physical activity of the kitchen users.

Acknowledgements: These examined issues constitute a part of the project: StarDust of the Baltic Sea Region Programme 2007 – 2013: The Strategic Project in Trans-national Commercial Activities in Research & Innovation, Clusters and in SME- Networks. This work was part-financed by the European Union (European Regional Development Fund and European Neighbourhood and Partnership Instrument). 5. REFERENCES BATORSKI, D. (2010): Między alienacją a adaptacją. Polacy w wieku 50+ wobec Internetu. Raport

Otwarcia Koalicji „Dojrz@łość w sieci” Warszawa. BRADLEY, N.; POPPEN, W. (2003): Assistive technology, computers, and Internet may decrease sense

of isolation for homebound elderly and disabled persons. Technology and Disability 15: pp. 19–25.

EDELKOORT, L. (2011): Design for the future. Compasses 15: pp. 44-53. FRONTCZAK, J. (2012): Handel internetowy w Polsce 2012. Analiza i prognoza rozwoju rynku e-

commerce 2012-2014.PMR Publications, Kraków. JĘDRZEJCZAK – SPRYCHA, A. (red.) (2011): Konsument przyszłości - kierunki rozwoju wzornictwa

przemysłowego w Polsce do 2030 roku. Raport Instytutu Wzornictwa Przemysłowego w Warszawie.

KOMISJA WSPÓLNOT EUROPEJSKICH (2007): Komfortowe funkcjonowanie osób starszych w społeczeństwie informacyjnym. Inicjatywa i2010. Plan działania w sprawie technologii teleinformatycznych i starzenia się społeczeństwa. Komunikat Komisji Parlamentu Europejskiego, Rady Europejskiego, Komitetu Ekonomiczno- Społecznego oraz Komitetu Regionów. Bruksela: COM (2007) 332.

KRISHNAMOORTHY, S. (2001): A smart video assistant for the kitchen. Massachusetts Institute of Technology, Cambridge, 20-21.

KRZYŻANOWSKA, Ł.; DANIELEWICZ, M. (2010): Mobilny Internet 50+. Nowe media w rękach starszych użytkowników. Instytut Socjologii Uniwersytetu Warszawskiego.

PALCZEWSKA, I.; BOCHIŃSKA, B.; BRYNDAL, D. (2011): Analiza stanu wzornictwa usług świadczonych drogą elektroniczną i perspektywy ich rozwoju w Polsce. Raport Instytutu Wzornictwa Przemysłowego w Warszawie.

QUINN, B. (2011): Design Futures. Merrell, London, 6-7, 42-45, 56-62. SKALSKA , Z. (2010): Światowe trendy w designie. Czy polskie produkty za nimi podążają? O!to

design. Spotkanie z polskim designem: pp. 20 - 29. SMARDZEWSKI, J. (2008): Projektowanie mebli. PWRiL, Poznań, 90-101, 112-113, 137-143. WANNINGER, C. (2009): Laying out the future. Architecrure and Design. Imm Cologne: pp. 87 – 93.


29

Influence of Tool Wear on the Quality of the Newly Formed Surface in the Drilling of Wood Composites

GORNIK BUČAR Dominikaa*– MERHAR Mirana – GOSPODARIČ Bojana

a Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana, Slovenia *Corresponding author: [email protected]

Abstract – The geometry of a drilling tool largely affects the quality of the newly formed surface. When drilling through a composite panel, the hole edge quality on the outlet side is significantly worse than on the inlet side, so the choice of the appropriate tool geometry is crucial. Even if the tool geometry is correct, tool wear also has a strong influence on the quality of the newly formed surface of the holes. With the tool wear, the force in the direction of drilling and torque around the axis of drilling are increasing which can affect to the delamination of particle board on the outlet side. The proposed model for hole edge quality prediction on the outlet side was tested on an experimental model where the cutting forces and torque in the drilling direction were measured, and the quality of the newly formed surfaces was evaluated every 180 holes using a visual method.

drilling / cutting forces / particle board / surface / delamination / quality of the edge 1. INTRODUCTION

In the furniture industry, furniture is most frequently made from surfaced, composite panels of medium (MDF) and low (PB) density. The drilling of holes through composite panels presents considerable problems in the assurance of a high quality edge on the outlet side of the hole. If the loads involved in drilling the hole through the composite are higher than the delamination value of the composite, the composite delaminates on the outlet side is most frequently unacceptable. Drilling loads depend on the technological parameters of machining, i.e., feed rate, tool rotation speed, tool geometry, and specimen properties. The structure and composition of the composite in particular have a strong influence on the tool wear as well.

Today, composite panels can contain a large portion of recycled old furniture, and thus also contain a relatively great amount of particles that are not of a wood and lignocellulose origin. Most frequently, these are ground metal structural elements (screws, door hinges, metal guides, etc.) of the recycled furniture or sand and stones which were introduced into the composite raw material during transport and handling of waste furniture before the recycling process. In the event that during the process of drilling the tool comes in contact with such a foreign body in composite panel, the tool is instantaneously damaged, which considerably changes the tool geometry and increases the thrust force, consequently affecting the composite delamination on the outlet side of the hole. In the case of automated production it is therefore reasonable to use a tool monitoring system, and if the tool is damaged, stop the production until the damaged tool is replaced.

Many researches have been conducted to determine the optimum technological parameters of drilling and their influence on the delamination of the layer on the outlet side of the hole can be found in literature. Most frequently the authors used MDF boards in their research (VALARMATHI et al., 2012; PAULO DAVIM et al., 2008; GAITONDE et al., 2008 and PALANIKUMAR et al., 2009). However, in 2013 a study of the analysis of drilling technology parameters in drilling particleboards (VALARMATHI et al., 2013) was published, where thrust force was also measured and analysed. The studies take no consideration of tool wear which, however, strongly and immediately affects the magnitude of thrust force in drilling.


30

2. EXPERIMENTAL SYSTEM

The measurements were performed using a three-axis, experimental CNC machine tool in the Laboratory of Mechanical Processing Technologies at the Biotechnical Faculty of the University of Ljubljana. The rated power of the tool spindle of the CNC machine tool is 3.2 kW at a nominal speed of 18000 rpm. A clockwise rotating tool intended for drilling holes, produced by Leitz, with designation 34077, 8 mm in diameter and with maximum drilling depth of 70 mm was used for drilling into a white, 18 mm thick, laminated particleboard. A cyclic drilling programme was used to drill series of 180 holes into the panels of 500 mm x 700 mm in size. The distance between holes was 15 mm, the tool feed rate was 1800 mm/min, and the tool speed was 6000 rpm. After each completed series of drilling, the thrust force was measured in the direction of drilling axis on the previously prepared five specimens, which were subsequently also used to determine the particleboard delamination factor. The thrust force was measured by a three-axis, piezo-dynamometer by Kistler, with designation 7292, which was connected to a Kistler 5019 amplifier. The amplifier output was connected to a multifunctional PCI interface with designation NI USB 6351, made by National Instruments, which made it possible to store force measurements with the sampling frequency of 100 kHz for further analysis. The measurement system block diagram is shown in Figure 1.

Figure 1. Measurement system block diagram

3. RESULTS OF MEASUREMENT

Equation 1 was applied to determine the particleboard delamination factor for the specimens used to measure the thrust force. Each specimen was photographed and the area of particleboard delamination was measured using the photo processing program, which is shown in Figure 2.

d

dF d

d = (1)

Fd - delamination factor dd - diameter of the circle drawn around delamination area [mm] d - hole diameter [mm]

The results of calculated delamination factors are recorded in Table 1.


31

Figure 2. Graphic presentation of determining the delamination factor

Table 1. The measured composite delamination factor of five test specimens after N drilled holes

N 185 1110 2220 3330 4440 5550

s1 1.00 1,21 1,24 1,31 1,44 1,28 s2 1.00 1,30 1,36 1,25 1,26 1,33 s3 1.00 1,24 1,25 1,45 1,32 1,26 s4 1.00 1,00 1,15 1,22 1,22 1,35 s5 1.00 1,16 1,43 1,20 1,35 1,34 1.00 1,18 1,29 1,29 1,32 1,31

Figure 3 shows the time course of the average of five measured thrust forces which were

measured in five specimens after the completed cycle of drilling 180 holes. However, the time course of the force, on the assumption of constant feed rate, shows that during the phase of drilling the force reaches two peaks, and both peaks represent structural properties of particleboard or its density profile. Thus, the two denser layers on the surface of particleboard have a greater specific cutting and thrust force. The somewhat lower first peak, as compared to the second one which is on the outlet side of the hole, can be attributed to the geometry of the tool used which was intended for drilling holes and therefore had a very small point angle. The second force peak which is encircled in Figure 3 occurs in the phase of drilling the bottom layer of particleboard, and in the event that it exceeds delamination value of the layer, it causes delamination of the particleboard on the outlet side of the hole. Figure 3 also shows the influence of tool wear on the magnitude of thrust force; i.e., after 5550 drilled holes the thrust force is increased by 84.2 %. Figure 4 presents the dependence of thrust force and the delamination factor on the number of drilled holes. The measurements show that the maximum permissible thrust force which has no influence on the delamination of outlet hole is 60 N.


32

Figure 3. Measured averages of force in the direction of drilling

Figure 4. The course of delamination factor Fd (red) and maximum thrust force F (green) of

drilling depending on the number of drilled holes

4. CONCLUSION

The results of measurements show a relatively good relation between thrust force magnitude and particleboard delamination factor, which also means that the maximum value


33

of thrust force can be used to determine the surface quality on the outlet side of the hole or the degree of particleboard delamination. It is assumed that similar results can also be expected in a different evaluation of the particleboard quality or the delamination degree on the outlet side of the hole and torque around the axis of drilling. The results of preliminary measurements indicate the possibility of using the thrust force measurement as a starting point in the regulation of adapting the technological parameters of the feed rate or the rotational speed of the tool to the optimum, or still the satisfactory degree of composite delamination on the outlet side of the hole. 5. REFERENCES GAITONDE, V.N.; KARNIK , S.R.; PAULO DAVIM , J. (2008): Taguchi multiple-performance

characteristics optimization in drilling of medium density fibreboard (MDF) to optimize delamination using utility concept. Journal of materials processing technology 196: pp. 73-78.

PALANIKUMAR , K.; PRAKASH, S.; MANOHARAN, N. (2009): Experimental Investigation and Analysis Delamination in Drilling of Wood Composite Medium Density Fiber Boards. Materials and Manufacturing Processes 24: pp. 1341-1348.

PAULO DAVIM , J.; CLEMANTE, V.C.; SILVA , S. (2008): Drilling investigation of MDF. Journal of materials processing technology 203: pp. 537-541.

VALARMATHI , T.N.; PALANIKUMAR , K.; SEKAR, S. (2012): Modelling of thrust force in drilling of plain medium density fibreboard (MDF) composite panels using RSM. Procedia Engineering 38: pp. 1828-1835.

VALARMATHI , T.N.; PALANIKUMAR , K.; LATHA , B. (2013): Measurement and analysis of thrust force in drilling of particle board composite panels. Measurement 46: pp. 1220-1230.


35

Increasing the Productivity of Enterprises with the 20 Keys Method

GRLADINOVIĆ Tomislava – PERIĆ Ivanaa*– STASIAK-BETLEJEWSKA Renatab – ŠKODA Petara a Wood Technology Department, Faculty of Forestry, University of Zagreb, Zagreb, Croatia

b Institute of Production Engineering, Faculty of Management, University of Technology, Poland


Abstract – Each production has its own specifics. These depend on many variables of both global and local character (e.g. global: roads, proximity of mills and forests, etc., local: availability of staff and necessary connections, production space, machines, etc.). All these particular characteristics affect production to a different extent. The role of managers is to put them all in balance, i.e. to create the most suitable climate for the development and growth of their company, production or trade. For quality problem-solving, the state of all production processes must first be determined, because only a systematic and realistic identification of problems results in long-term success. Wood-processing industry requires a very deep understanding of a specific problem and a cautious approach. The research polygon for this study was a furniture manufacturing enterprise, in which time and material flow were monitored and workplaces involved in the production process examined. Based on that, a proposal was put forward with solutions for improving the enterprise productivity. As a guide through the reengineering method, the 20 Keys Method was used.

furniture manufacturing / wood processing / the structure of time / flows of materials / reengineering / 20 keys method 1. INTRODUCTION

Reengineering is defined as the fundamental rethinking and radical redesign of production and business processes to achieve improvements in the effects related to costs and business quality (HAMMER – CHAMPY, 1994). This definition reconsiders businesses in a new way with the aim of remaping dramatic improvements in business performance and measuring business performance indicators. These indicators are designed for end user and focus on them. Reengineering radically changes some traditional ways of process improvements.

From the standpoint of business strategy, reengineering claims to optimize the performance of administrative and supportive processes, as well as optimize the performance of operative processes. The goal is to achieve competitive advantage and switch the nature of competitive struggle towards changing the industrial structure in the direction favourable for an enterprise. The innovative potential of information technology and a better use of human potential provide the main sources of competitive advantage; hence, they play a crucial role in reengineering.

The introduction of reengineering requires from individuals and working teams to perform the majority of business processes independently; in other words, all their know-how and skills are fully engaged. For this reason, employees enjoy the rights which in a traditional organisation are given only to managers. It should be emphasised that reengineering requires a different approach to employee treatment. The employees are treated in a „more relaxed“ manner, there is no pressure on them and their achievements are highlighted and awarded, all with the goal of enhancing their creativity and thinking and making them the key generators of ideas and innovations. An enterprise is public-oriented rather than closed in its own business and production frames. Reengineering refutes processes which, either directly or indirectly, do not create value-added products (degree of customer satisfaction).

According to FIGURIĆ (2000), the central place in the reengineering philosophy is given to processes. Thus, a company's approach to processes and more superior organisation is


36

primarily prompted by the fear of their competitors' „catching up with and outrunning them“. The globalisation of furniture markets, the rapidly changing world, the ever more demanding customers and increasing competition constantly drive companies to reconsider their business operations. 2. THE 20 KEYS METHOD

One of the reengineering methods is the 20 Keys Method. Created by Iawo Kobayashi of Japan and based on the Toyota production system, this programme of measures is geared towards permanent business development. The 20 Keys Method has been adopted by more than 500 companies worldwide (e.g. Sanyo, Gillete, Seiko), including some companies in the neighbouring countries. This method consists of very simple measures which business systems should apply in practice. The keys and tasks are presented in the form of advice, which, implemented and adhered to lead to a higher organisational level and diminish the needs of production resources, at the same time increasing the efficiency.

Key 1 The task is to clean and organize a workplace (Table 1). At first sight, this is an absurd advice. However, a more careful examination of companies shows that this first key is absolutely necessary. Order is the condition of making work easier, but in a large number of cases it has not been achieved.

Key 2 Rationalizing the System, Goal Alignment. A clear and well organized goal alignment system is the key to efficient guidance. This is what Key 2 is all about. Particular emphasis is put on team work and guidance towards the goal, as it integrates the interests of a company and an individual.

Key 3 Small Group Activities. Work in small groups enhances innovations, increases company adaptability and strengthens readiness to participate. This is why Key 3 leads to better efficiency and success.

Key 4 Reducing Inventory. Major savings can be made in the field of inventory and products reductions. Key 4 envisages improvements in this field.

Key 5 Quick Changeover Technology. Adaptability is the key to survival. Changeover technology is a must in this field. However, organisational conditions to reach this goal are often neglected. This is why Key 5 advises savings by shortening production cycles.

Key 6 Manufacturing Value Analysis. Cutting down on unnecessary tasks and on work that does not add to product value saves time and other resources needed for useful work. This is why this Key proposes value analysis in order to eliminate superfluous work.

Key 7 Zero Monitor Manufacturing. Monitoring and supervision is unproductive work per se. If eliminated without any harm, we have done a useful act. Although not completely possible with systematic work, it can still be achieved to a great measure.

Key 8 Coupled Manufacturing. Coupled manufacturing is easier to plan, supervise and guide. This is why the goal of a good organization is to achieve coupled manufacturing. Key 8 proposes a method of linking production processes and decreasing inventories.

Key 9 Maintaining Machines and Equipment. Maintaining machines is the core condition of continuous production. It is not surprising therefore, that Key 9 proposes exactly this. Preventive maintenance will allow for easier accomplishment of production processes.

Key 10 Work time Control. Work time control is an important factor in every production and business process, and this is why it requires particular attention. Efforts are geared towards full use of work time, as suggested by this Key.

Key 11 Quality Assurance. Quality assurance is the key to success. This is why the Key suggests a set of tasks intended to eliminate mistakes and increase self-control.

Key 12 Developing Supplier Cooperation. A supplier is not a partner. A partner participates in business results; hence, the relationship between partners is more intimate and


37

responsible. Rationalization of the suppliers' production processes directly benefits the customer. Key 12 is all about this issue.

Key 13 Eliminating Wasteful Human Activities. Perform only those activities that increase value and decrease resource use. Every unnecessary activity is irrational. This Key expands this idea to the entire business and not only to the product referred to in this Key.

Key 14 Empowering Employees to Make Improvements. Improved rationalization should not be in theory only. Employees should be trained to introduce improvements.

Key 15 Skill Versatility and Cross Training. Production will be more versatile if employees are trained to perform different tasks. It will also be possible to deploy them to different workplaces. This requires additional training.

Key 16 Production Scheduling. Planning is given particular attention. This is understandable, since planning entails predicting the events and avoiding mistakes.

Key 17 Efficiency Control. Efficiency control is the condition of success. It forms the basis for a motivation and stimulation system and enables more efficient and realistic planning.

Key 18 Using of IT Systems confirms that the introduction of microprocessors enhances rationalisation.

Key 19 Conserving Energy and Materials. It is not surprising that conserving energy and materials enhances rationalization.

Key 20 advises the implementation of Leading Technologies, provided that the guidelines contained in the keys described above are on the required developmental level and degree. Otherwise, there may easily be negative effects (HAMMER – CHAMPY, 1994). Table 1. Cleaning and Organising to Make Work Easy (HAMMER – CHAMPY, 1994)

Key 1 Cleaning and Organising to Make Work Easy Level 1 Level 2 Level 3 Level 4 Level 5

Characteristic Characteristic Characteristic Characteristic Characteristic

Cigarette butts, rolls of paper and tools are scattered

around.

Litter and different items are scattered on the floor and walls. Transport routes

are not free.

Transport routes are free. The tools

are still visibly scattered around.

The machines and equipment are

clean. The storage spaces are defined

and organized.

Cleaning is done regularly and constantly.

Workplaces are clean and the

tools are stored and clean.

Step up to a higher level





Check all the spaces. Check the workplaces and remove all litter, superfluous tools

and materials.

Check all the walls and put

away litter and superfluous tools

and materials.

Check the drawers and

cabinets and sort out the tools and other items. Do

not lock the offices.

Regularly tidy up, clean and keep

your workplace in order. Visually check the tools and inventory.

Important steps

Important steps

Important steps

Important steps

Important steps

Do not store things on the

floor. Discard all the things you

know you will not need.

Share the responsibility for

order. Make it clear that

employees are responsible for

the cleanliness of their workplaces.

All things should be immediately at

hand. The frequently used tools should be easily accessible and other tools should be put

away.

Introduce an experimental line, but the workplace

with parts and tools should be arranged on a self-service principle.


38

3. REENGINEERING OF THE STUDIED PLANT USING THE 20 KEYS METHOD

After careful data examination and analysis of the condition in the observed plant, the 20 Key Method was proposed with the goal of improving productivity and launching a competitive assault on the market, since this method systematically and favourably affects all manufacturing processes. Improvement is achieved by following the keys that determine the characteristics of different levels (from the poorest 1 to the best 5). Based on these levels, the climb to a higher level is suggested and important steps are made into higher levels of business production.

Key 1 Cleaning and Organizing the Workplace. Level 2 was detected – different items scattered across the workplace. Transport paths are not free. Workplaces should be examined and all unnecessary items, materials and tools should be put away. An important step is to share the responsibility for order and make it clear to the employees that they are responsible for their workplaces.

Key 2 Organizing the System, Goal Alignment. Level 2 was found – the organisation is clear, but the tasks are set down imprecisely. Goals should be set and decisions made on who should do what and how. Clear goals should be made to match the level that corresponds to the department, stage of work or an individual.

Key 3 Small Group Activities. Level 1 was detected - there is no willingness to work in groups. A formal system of improvement adoption should be implemented. Proposals should be rewarded and the importance of joint employee effects per group should be emphasised.

Key 4 Reducing Inventory. Level 3 was detected – inventories are being reduced (but not sufficiently). All the machines and lines should be rearranged (related to technological processes for room doors, wardrobes and kitchens), and production should be organized so that fewer interphase inventories are needed. An important step involves the introduction of a material ordering system and simplifying of semi-finished products.

Key 5 Quick Changeover Technology. Level 2 was detected –responsible employees understand the importance of quick tool change. Participation at all levels should be encouraged and methods of achieving systematic improvement should be implemented.

Key 6 Manufacturing Value Analysis. Level 3 was found – in some processes improvements are being systematically prepared. A plan of implementing improvements should be drawn up and documentation for an organized approach to improvements should be prepared. An important step involves setting the goals to shorten manufacturing time.

Key 7 Zero Monitoring Manufacturing. The plant was found not to posses the machines needed to implement Key 7.

Key 8 Coupled Manufacturing. Level 2 was detected – the importance of continuous, integrated production is understood. Strategies to integrate production should be developed and studied. An important step involves reducing the inventories and controlling them in order to enable coordinated activity.

Key 9 Maintaining Machines and Equipment. Level 1 was found – machines operate until they break down. Preventive machine maintenance should be introduced. Important steps involve detecting and singling out the machines that affect production flows most and prepare checking lists for preventive maintenance.

Key 10 Work time. Level 1 was detected – work time and rest periods are left to employee discretion. The beginning of work time should be determined by e.g. introducing morning meetings. Meetings should be well prepared and purposeful.

Key 11 Quality Assurance. Level 2 was detected – workers control their products. However, one of the characteristics of a particular type of production is that every manufactured part is “tested”, which requires setting the machine for every part individually. Accordingly, quality assurance is at level 4. It should be pointed out that effort should be directed towards establishing a system of eliminating mistakes.


39

Key 12 Developing Supplier Cooperation. Level 5 was found – the supplier becomes a partner in the proper sense of the word.

Key 13 Eliminating Wasteful Human Activities. Level 1 was found – there is no awareness of the importance of detecting superfluous work. It should be made clear to the employees that effort without effect is meaningless and represents a waste of time. Only those operations which the customer is ready to pay for should be performed.

Key 14 Empowering Employees to Make Improvements. Level 2 was found – it is possible to prepare minor improvements. It would be important to accept the fact that the 20 Keys Method increases the available space for company innovations.

Key 15 Skill Versatility and Cross Training. Level 5 was detected – the company freely deploys employees, thus successfully meeting environment demands.

Key 16 Production Scheduling. Level 1 was detected – terms of deliveries are not obeyed. Production should be planned and orders followed. It is important to set down the time needed for production.

Key 17 Efficiency Control. Level 1 was detected – an indirect system of efficiency control is in use. The necessary number of operations and times per group of products should be determined. Groups of products should be shaped according to the number of type of operation.

Key 18 Implementing IT Systems. Level 2 was detected – computers are used for simple jobs. The importance of microprocessors should be enhanced. The employees should be trained to use microprocessors and computers.

Key 19 Conserving Energy and Materials. Level 2 was found – the employees are aware of the importance of saving energy and materials. Some obvious savings should first be made. The awareness that knowledge is the key to success is very important.

Key 20 Implementing State-of-the-Art Technology. Level 2 was detected – the company does not have the possibility to implement new technologies. The financial construction should be closed and programmes of technology development proposed. It is important to coordinate technology development with product development. 4. CONCLUSION

The 20 Key Measures and Methods have been implemented in the studied plant with the

goal of improving and optimizing production. Guidelines for further growth and development of production and business have been installed.

Manufacturing processes in the company were analysed and a solution was made by setting a clear organisation of the company’s mission and vision through a business and production function. Examination of the current state of the company revealed low levels of the majority of business standpoints. It is difficult to analyse manufacturing with traditional methods, which are formulated for serial industrial and mass production systems. The reasons for this are found in the characteristics of the observed manufacturing plant. This is the reason that plant reengineering is proposed to address decision-making processes, whereby the 20 Keys Method would constitute the main reengineering tool.

The procedures and methods of increasing productivity that are developed at given entries and presented in the subject material make it possible to achieve considerable improvements and better effects through systematic work. 5. REFERENCES BIZJAK, F. (1994): Inovativno vođenje in gospodarenje podjetja. Univerza v ljubljani, Biotehniška

fakulteta, Oddelek za lesaravo, Ljubljana.


40

BIZJAK, F. (1997): Reinženjering in razvoj podjetja. Educa, Nova Gorica. BIZJAK, F.; PETRIN, T. (1996): Uspešno vođenje podjetja. Gospodarski vestnik, Lubljana. FIGURIĆ, M. (1987): Organizacija rada u drvnoj industriji. Narodne novine, Zagreb. FIGURIĆ, M. (2000): Proizvodni i poslovni procesi u preradi drva i proizvodnji namještaja. Šumarski

fakultet Sveučilišta u Zagrebu, Zagreb. FIGURIĆ, M. (2003): Menadžment troškova u drvnotehnološkim procesima. Šumarski fakultet

Sveučilišta u Zagrebu, Zagreb. GOJANOVIĆ, J., (1977): Ekonomika i organizacija proizvodnje. Informator, Zagreb. HAMMER, M.J.; CHAMPY, J. (1994): Reengineering corporation. Harper Business, New York. TAKEDA, H. (2006): The Synchronized Production System. Kogan Page, London, Philadelphia ZELENOVIĆ, D. (1973): Proizvodni sistem. Naučna knjiga, Beograd. ZELENOVIĆ, D.; RADLOVAČKI , S. (1984): Program za rast produktivnosti. FTN-Institut za industrijske

sisteme, Novi Sad.


41

Kitchen Furniture - Accessibility of Storage and Working Space

HROVATIN Jasnaa*– VIŽINTIN Jožeb a Faculty of design - associated member of University of Primorska, Ljubljana, Slovenia

b University of Ljubljana, Faculty of Mechanical Engineering, Ljubljana, Slovenia *Corresponding author: [email protected]

Abstract – The number of senior citizens is rapidly increasing. According to statistical prognoses, 36 % of world population will be older than 60 years by the year 2030. The share of people older than 80 years will increase to 11.4 % by 2050. We were interested in the suitability of commercially affordable furniture for the needs of the elderly, because a comfortable apartment is particularly important for the elderly who spend most of the time in their homes. The aim of this study was to determine to what extent kitchens manufactured are suitable for elderly people regard to the accessibility of goods stored in the cupboards. The study was carried out using a computer simulation model. The results show that the efficacy of the volume in wall cabinets is not optimal for the elderly. Also problematic are the height and depth of the kitchen counter. Due to the large differences between male and female height and between races it is impossible to determine the optimal dimensions of the elements, since the size of kitchen elements is closely related to the size of the people. Based on the measurement analysis, we will show same proposals how to improve the kitchen furniture for the elderly people.

furniture / dimensions / ergonomics / kitchen / elderly / design 1. INTRODUCTION

Higher standard, nutrition and well regulated health care enables a high increase of the share of the elderly each year. According to statistical prognoses, 36 % of world population will be older than 60 years by the year 2030 (HILDERBRAND, 2002). This sets completely new demands for residential and public facilities. The decrease of the birth rate and the mortality rate are also changing the age structure of Slovenians.

In the field of furniture designed for elderly are very important anthropometry and ergonomics. Few studies have focused on the correlation between ergonomics and kitchen furniture design for the elderly. Some authors (HROVATIN, 2002; TRAJKOVIĆ – PREKRAT, 2002; PISSAREVA – JIVKOV , 2009) have addressed the issues of kitchen design by means of inclusive design, which generally includes the elderly and special needs individuals. KIRVESOJA et al. (2000) have found that the elderly have greater difficulty in adjusting to inappropriately high worktops than people under the age of 65. The fact is that kitchen work could be significantly eased with the appropriate design and suitable arrangement of kitchen cupboards. In designing kitchens, the optimal depths and heights of worktops and storage places should also consider accessibility and spinal load.

PENNATRHUR and DOWLOING (2003) state a limit of vertical accessibility of 180 cm. Of course, accessibility of wall cabinets is lower if a person is standing in front of low cupboards on the floor or by the kitchen worktop. Accessibility also depends on the size and the age of the user. The optimal storage zone is between 800 and 1100 mm. Both visibility and accessibility are reduced at heights between 1400 and 1700 mm. At this height, the majority of men and women are able to store light items on the edges of shelves, however, accessibility above 1700 mm is considerably reduced for most people. Apart from height, the depth of the cupboards and cabinets plays an important role in accessibility and visibility. Pheasant recommends that the depth of shelves at heights between 800 and 1400 mm should not exceed 600 mm. At heights below 800 mm, the depth of the shelves should be up to 450 mm and at heights above 1400 mm, the depth should be up to 300 mm (PHEASANT – HSDRIGRAVE, 2006).


42

PHEASANT (2006) state that a shelf depth of 300 mm and height of up to 1400 mm are suitable for 95 % of the elderly. Nevertheless, if there is an obstacle in front of the cupboard, like a worktop, the height should not exceed 1350 mm. Shelves placed below 300 mm are not suitable for people who have problems kneeling or bending (KIRVESOJA et al., 2000) Deep shelves are particularly impractical, and the author suggests that shelves be placed above a height of 500 mm for the elderly.

The elderly have greater problems in reaching objects than younger people (PANERO –

ZELNIK , 1979), due to the occurrence of arthritis and other conditions that restrict joint movement. Also, elderly users have reduced muscular strength and joint mobility due to the ageing process. To the greatest possible extent, the majority of items should be stored between the knuckle and shoulder heights so that elderly users are not subjected to bending and overreaching demands (KOTHIYAL – TETTEY, 2001). Anthropometric evaluation of vertical accessibility in a standing position for British adults shows that accessibility between the young and the elderly differs by an average for 170 mm for males and 147 mm for females. The difference until the age of 80 is considerably smaller, namely, 120 mm for males and 80 mm for females.

An article from PENNATHUR et al. (2003) described the functional limitations of the elderly. Objects in wall cabinets in their kitchens could be reached without difficulty or assistance by 26.67 % of females involved in the research, with assistance by 56.67 %, while 16.67 % of females could not reach the objects. In the low cupboards, 12.9 % of females did not have problems reaching the objects, 35.48 % of females were able to reach the objects with assistance, whereas 35.48 % of females found the objects in the low cupboards almost unreachable. Accessibility of food in the refrigerator is better, since 87.1 % of females did not have any problems, 9.68 % required assistance and for 3.23 % of females, the food was almost unreachable. For this reason is recommended that, it is better to use a lower percentile (5th percentile) in order to accommodate as large a share of the population as possible.

A 900 mm high worktop is too low for about half of the females and almost all males, which is why work in the kitchen is often related to pain. (PHEASANT – HSDRIGRAVE, 2006) Nevertheless, a higher worktop means that wall cabinets should be placed higher, making the upper shelves even more difficult to reach, especially for the elderly. Furthermore, it is necessary to consider that the height of the elderly is getting smaller over time. Therefore, the height of the worktop for the elderly should be lower than for young people.

The objective of this study was to determine the extent to which kitchen furniture manufactured by the Slovenian furniture producers is suitable for users of different age groups and the accessibility of objects in the wall cabinets. Furthermore, basic principles upon which kitchen furniture should be designed to meet the needs of the elderly are proposed based on the measurement analysis, so as to enable maximal productivity with minimal time and energy consumption without harmful consequences for health.

According to our analysis Slovenia does not have manufacturers of standard furniture for the elderly people. Orders for individual clients carry small carpenter’s workshops. In this paper we present some results of our analysis. Based of the analysis results we will show same proposals how to improve the kitchen furniture for the elderly people.

2. MATERIAL AND METHODS The research was carried out using a computer simulation model. 3D modelling

technology is already being integrated into the design of other products (MIJOVIĆ et al., 2008). A similar research was also carried out by SMARDZEWSKI (2009). A standardised kitchen furniture manufacture was included in this study and one typical kitchen set was selected. The 3D CAD programme (MegaCAD, manufacturer MegaTECH and Megatischler


43

manufacturer Planles, version 2009) was used to design the kitchen furniture as life-size furniture. In the study, the focus was on the accessibility of objects in the wall cabinets.

Accessibility was tested using a person designed in three sizes. The data for males and females of three age groups (19–25 years, 26-45 years and 45–65 years old) was used in determining sizes. The model person was placed into the kitchen designs and we detected height accessibility in the wall cabinets (Figure 1). The model was placed beside the worktop so that the end of the foot was 30 mm from the line of the low cupboard base.

Figure 1. 3D model of a person and the kitchen furniture 3. RESULTS

Using the computer simulation model of a person and the kitchen furniture, we observed

the intersection of accessibility in wall cabinets for different male and female age groups in the selected kitchen. In Figure 2 the area of accessibility is hatched and in Graph 3 the calculation of accessibility is presented as a percentage.

Figure 2. Placement of the female and male models, ages 19–65

50 %ile Area of

accessibility (dm²)

Total area (dm²)

Accessibility (%)

Female, 19–45 years 4.9 21.7 22.6

Female, 45–65 years 4.7 21.7 21.7

Male, 19–45 years 11.0 21.7 50.7

Male, 45–65 years 9.4 21.7 43.3


44

Figure 3. Accessibility in wall cabinets

Height accessibility depends on the height of the wall cabinets and the distance of the wall cabinet’s lower edge from the floor. This dimension depends on the height of the worktop and the height of the interspace between the worktop and the bottom of the wall cabinet. The interspace is 536 mm. The height of the space between the worktop and the bottom of the wall cabinet depends on the high cupboards if the top of the high cupboard is intended to be at the same level as the top of the wall cabinet. Nevertheless, it is desirable that the height of the interspace is larger so that the wall cabinets do not obscure the view on the workspace, while on the other hand, the height should not be too high due to accessibility of the objects in the wall cabinets.

Graph 3 shows that the height accessibility is lower for the elderly than for young people as a result of decreasing height in the elderly. It should also be noted that if the worktop is placed at a higher level, the wall cabinets are moved higher, which will, again, reduce accessibility. If we consider the recommendation of (PISSAREVA – JIVKOV , 2009) that the recommended height of the worktop is from 80–100 mm measured under the curved elbow, we can see that the worktop is too low for both males and females.

Figure 4 shows accessibility with the height of the worktop as found in tested kitchen, and the height accessibility if we adapt the height of the worktop to the height of the users, namely to 50 % of males and females (Table 1). If the height of the worktop is adapted to the height of the user, the difference in height accessibility between males and females is decreased, although males are on average taller than females (Table 2, Figure 5).

Figure 4. Height accessibility for females and males, ages 19–45 in test kitchen (a, c), where the height of the worktop meets ergonomic requirements (b, d).

Table 1. Accessibility at the height of the worktop that meets ergonomic requirements

50 %ile Area of accessibility

(dm²) Total area

(dm²) Accessibility (%)

Female, 19–45 years 3.6 21.7 16.6

Male, 19–45 years 7.1 21.7 32.7


45

Table 2. Difference in accessibility concerning the height of the worktop and gender

50 %ile Accessibility at the height of the worktop in tested kitchen

(%)

Accessibility at the height of the worktop that meets the

ergonomic requirements (%) Difference (%)

Female, 19–45 years 22.6 16.6 6

Male, 19–45 years 50.7 32.7 18

Difference in accessibility between man and women

28.1 16.1

Figure 5. Graphical display range depending on the amount of counter and gender

3.1. Same proposals for improving design

Considering the results of analysis we have designed same kitchen furniture elements for people which are older than 65 years. In the interdisciplinary design group designers, architects, mechanical engineers, electric engineers, wood engineers and ergonomics experts have taken active part. As a result of the work different kitchen elements for the elderly were designed with personal security and the ability to perform kitchen tasks faster and more easily in mind. Figure 6 shows the solutions how to solve the problem with the kitchen dishes which are located higher than 150 cm or lower than 65 cm.

Figure 6. New proposal for kitchen elements design

The optimal storage zone is between 800 mm and 1100 mm (PENNATHUR – DOWLING, 2003) thus in the area of the worktop which is without cabinets, as in standard kitchen furniture the cupboards are positioned under the worktops and above as wall cabinets. The solution to this problem is high cupboards or cabinets placed on a deeper worktop. Figure 7 shows accessibility in a cabinet placed on the worktop with a body inclination of 30° and 55°.


46

Figure 7. Placement of the female model, ages 19–45, in kitchen, with a body inclination of 30° and 55°

Since the cupboards under the worktop are deeper, the volume of these cupboards is 48 %

greater, meaning that by increasing the depth of these cupboards, the storage space has increased. Nevertheless, considering that the elderly commonly have problems with bending and kneeling, shelves placed below 300 mm should be avoided, and deep shelves are especially impractical (KIRVESOJA, 2000). A better solution would be cupboards with drawers that can be fully pulled out or with lift drawers.

With cabinets placed on the deeper worktop, additional storage space with good accessibility has been acquired. Accessibility is increased by 70 % if the body is inclined forward by 30° and by 91 % if the body is inclined by 55°.

4. DISCUSSION

Accessibility is higher for males than for females, which is logical due to differences in their body heights. On the other hand, accessibility in the wall cabinets also depends on the height of the cupboards under the worktop and the distance from the lower edge of the wall cabinet from the floor. If the height of the worktop is adapted to the height of the user, the wall cabinets are placed higher and the difference in height accessibility is no longer as prominent (Figure 5).

This study has shown that in wall cabinets higher than 600 mm, the efficiency of the volume where objects are easily accessible is less than 30 % for females. The percentage is even smaller if the height of the worktop is 100 mm under the curved elbow, meaning the space in the wall cabinets is used inefficiently, especially if the wall cabinets are higher.

The results coincide with the results of a study (PHEASANT – HSDRLGRAVE, 2006) that found that accessibility is reduced at heights between 1400 and 1700 mm. Since the lower edge of wall cabinets is usually above 1400 mm, this means that wall cabinets are problematic in terms of comfortable accessibility. It is evident in the figures showing a 3D model of a person that accessibility on the lower shelf is satisfactory, whereas the objects stored on the second shelf are difficult to reach.

Accommodation for the elderly should take their physical and emotional characteristics into consideration. Muscle strength decreases by 40–50 % between the ages of 40 and 80 (KIRVESOJA, 2000). The changes in muscle function are even more apparent after the age of 70. Besides this, the majority of the elderly cannot actively carry out plantar flexion in their ankle (tiptoeing), which results in even lower height accessibility. In comparison with young people, the area of comfortable accessibility is decreased for the elderly due to their reduced musculoskeletal abilities. That is why it is even more important for the elderly to have


47

ergonomically designed equipment, which considers anthropometry and enables comfortable accessibility. It is even more important for the elderly than for young people to have kitchen furniture that is especially designed to meet their needs. We believe that the cabinets placed on the worktops are undoubtedly a better solution for the elderly than wall cabinets, since the accessibility in the wall cabinets is even lower for the elderly than for people up to the age of 45. Therefore, we believe that cabinets placed on a deeper worktop are for the elderly much more suitable as wall cabinets, the solution also represent a drop-down shelves. 5. CONCLUSIONS

Most elderly who would like to renovate their kitchen in order for it being used for the

rest of their lives, do not have adequate supply in the market. The kitchen furniture produced by the Slovene manufacturers is not suitable for the elderly. This study has shown that the efficiency of volume, where objects are comfortably accessed in the wall cabinets higher than 600 mm, is lower than 30 % for females, indicating that the storage space in the wall cabinets is used inefficiently. The study conclusions are as follows:

- Objects stored in the wall cabinets higher than 600 mm are accessed with difficulty and therefore a version of the kitchen furniture with deeper worktops and cabinets positioned on the worktops is recommended if the room size enables such a solution. Good solution is also a drop-down shelf.

- Cupboards placed under the worktop should have drawers that can be fully pulled out or lift drawers that allow for a better view of the displayed objects, easier loading and emptying without having to remove other objects, better efficacy of volume and loading and emptying without the need for bending.

- Incorporate the intelligent technology a much as possible. 6. REFERENCES HILDERBRAND, H. (2002): Für Ältere und Behinderte. BM 57. (3): 36. HROVATIN, J. (2002): Ergonomics in the kitchen – Theory and practice, International symposium . “Wood is good – Furniture, human, design”. Croatia, Zagreb, oct, 2002. pp. 51-58. KIRVESOJA, H.; VÄYRYNEN, S.; HÄIKIO . (2000) Three evaluations of task-surface heights in elderly . people's homes. Applied Ergonomics 31. (4): pp. 109-119. KOTHIYAL , K.; TETTEY, S. (2001): Anthropometry for Design for the Elderly. International Journal of . . Occupational Safety and Ergonomics. 7. (1) pp. 15-34. MIJOVIĆ, B.; UJEVIĆ, D.; BAKSA, S. (2001): Visualisation of anthropometric measures of workers in . computer 3D modelling of work place. Collegium Antropol. 25. (1): pp. 639 – 650. PANERO, J.; ZELNIK , M. (1979): Antropološke mere i enterier. Novi Dani, Beograd, 1979. PENNATHUR, A.; DOWLING, W. (2003): Effect of age on functional anthropometry of older Mexican . American adults: a cross-sectional study. International Journal of Industrial Ergonomics, 32. (1): . pp. 39-49. PHEASANT, S.; HSDRLGRAVE, C.M.; (2006): Bodyspace, Antropometry, Ergonomics and the Design of . Work. Third edition. London, Taylor and Francis 332. PISSAREVA, E.; JIVKOV , V. (2009): Kitchen furniture design for people with physical disabilities, International symposium. “Wood is good – new materials, quality and design of products”. Croatia, Zagreb, Oct, 2009. pp.85-90. SMARDZEWSKI, J. (2009): Anthropotechnical aspects of furniture design. Drvna Industrija, 60 15 TRAJKOVIĆ, J.; PREKRAT, S. (2002): Furniture for mobility-impaired persons, International . symposium “Wood is good –Furniture, human, design”. Croatia, Zagreb, oct, 2009. pp. 111-120.


49

Study on the Gluing Abilities of Solid Surface Composites with Different Wood Based Materials and Foam PVC

JIVKOV Vassila*– SIMEONOVA Ralitsaa – MARINOVA Assiaa – GRADESVA Galinaa

a Department of Interior and Furniture Design, University of Forestry, Sofia, Bulgaria *Corresponding author: [email protected]

Abstract – The present study is related to the gluing abilities of solid surface composites with different wood based materials and foam PVC boards. Acrylic based solid surface material with thickness of 6 mm were bonded to five types of different substructure materials – laminated and non laminated particleboards, plywood, MDF and foam PVC boards. Three types of adhesives were used – one component polyurethane, rubber based and PVAc. The test has been done according to BDS EN 205. The results show that the type of adhesive and the type of the material of the substructure have significant influence on the adhesion strength. The highest measured tensile shear strength was achieved by rubber based adhesive and substructure from plywood. As a substructure the highest abilities for gluing have wood based materials. For PVAc adhesive with wood based materials as adherent, different from BDS EN 205 test method should be used.

solid surface composites / gluing abilities / adhesion tensile shear strength / wood based materials 1. INTRODUCTION

Solid surface is a generic name given to a polymerised decorative surfacing material. Solid surface material has been invented by DuPont™ in the 1967 and is known as Corian®. It is a solid, non-porous, homogeneous surfacing material composed of ±1/3 acrylic resin (also known as PolyMethyl MethAcrylate or PMMA) and ±2/3 natural minerals. The main mineral is Aluminium TriHydrate (ATH) derived from bauxite, an ore from which aluminium is produced. Aluminium Trihydrate is a common primary ingredient present in most solid surface materials and accounts for as much as 70 % of the total product. In the last decades solid surface material became well known and very popular and is generally made, but not limited to, using an acrylic or polyester resin as bonding agent. Such materials are made in a variety of nominal thicknesses, for example 3, 4, 6, 8, 10, 12 mm etc. depending on the type of applications and market requirements. Due to their properties solid surface materials have many advantages: moisture resistance, resistance to household chemicals and boiling water, safe for food contact, seamless joints, surface is renewable, easy to clean, thermo formable, colourful, non-toxic and etc. That is why it is an advanced composite product used as a decorative material in a variety of residential and commercial applications. Solid surface material offers design versatility, functionality and durability.

Solid surface composites are widely used in furniture. As a decorative surface material they are glued to a substructure which could be wood based material or plastics. Typical application of this kind of sandwich panel is kitchen worktops or bathroom worktops. Another possibility is a combination of a different structural materials and one of them is solid surface material. Recommendation of the manufacturers is when the solid surface material has to be glued to a substructure made of MDF or plywood to be used flexible silicone, rubber based or polyurethane elastic adhesive. This is because of different thermal expansion of the materials. Many studies have been done in the field of bonding strength of wood and wood-based materials. Some of them were investigating the type of testing (KONNERTH et al., 2006; KYUCHUKOV, 2010). The test for bond strength of scarf joint and lap, as well the joint testing method for beech and spruce solid wood shows different type of failure with different test methods (KONNERTH et al., 2006). The failure mode with standard lap joints is mainly wood


50

failure and scarf joint failed in the bond line. Predicting of shear strength of test specimens of wood adhesive bonds have been studied by SERRANO (2004) and it was found that the prediction of bond line strength was highly depending on both the specimens’ type used and adhesive properties, such as strength fracture energy, and the shape of stress slip behaviour of the adhesive layer. But it was not found any information in the technical and scientific literature about the gluing ability and adhesion strength of solid surface materials with other materials. Glue bond quality and durability can be affected in many ways, such as density, porosity and smooth surface of the adherent (DUNKY et al., 2002) or non water absorption ability of the solid surface material. Therefore, it is very important enough knowledge about the gluing ability and adhesion strength of solid surface materials with other wood based and non-wood materials with different type of adhesives to be established. 2. METHODS AND MATERIALS

There is no standard which is intended to establish test methods for evaluating the gluing

ability or adhesion strength between wood based materials and composites like solid surface. Due to the fact that the adhesives manufacturers are giving recommendations about the strength characteristics of adhesives according to BDS EN 205 for the purpose of this study this standard was used as test method. Another possibility is to be used BDS EN 13354:2008 (KYUCHUKOV, 2010)

2.1. Materials

Acrylic based solid surface material made in sheets with thickness (S2) of 6 mm was used for this test and was purchased from Kolpa, Slovenia. Material has density of 1700 kg/m3, MOE – 9700 N/mm2 and bending strength – 70 N/mm2.

Laminated (S1=18 mm) and non laminated particleboards (S1=16 mm), MDF (S1=6 mm) and plywood (S1=17 mm) as a mass produced panels were used as wooden substructure materials. Foam PVC boards (S1=19 mm) were used as non-wooden materials. They are light, high-strength alternative to a wooden materials, which is designed to eliminate heavy and hard to handle materials. PVC foam board is waterproof and do not distort in moisture or water, so it is good choice to do furniture like bath cabinet and kitchen worktops.

2.2. Adhesives

Tree types of adhesives have been used for the purpose of this study – one component polyurethane, rubber based and PVAc. A commercial product Sikaflex®-11FC+ was selected as PUR adhesive. It is one part, moisture curing elastic joint and multipurpose adhesive based on polyurethane, suitable for indoor and outdoor application. The joint width must be at least 10 mm but less than 35 mm. Hand pressure were used to set the element to be bonded in the correct position.

Rubber based adhesive with commercial name Moment Express Fix PL 600 was used as a second type. It is solvent base, styrene-butadiene copolymer, fast gluing and multipurpose adhesive.

Folco Lit X 3000 PVAc based adhesive was taken as representative of the most commonly used adhesives in the woodworking industry. It is an unfilled adhesive with cross linkable groups with an application for surface bonding and assembly gluing as well gluing of softwood and particleboards. Folco Lit X 300 PVAc adhesive has good water resistance with a durability class D3 according to BDS EN 204 and good heat resistance: ≥ 7 N/mm2 according to DIN EN 14257 (WATT 91).


51

2.3. Methods

2.3.1. Description of tests sample

Test samples have been prepared according to BDS EN 205 (Figure 1). The single-lap joint, in which two sheets of different material were jointed together with an overlay of 10 mm have been produced. All five substructure materials were bonded with one component polyurethane and rubber based adhesive. Plywood, non laminated particleboard and MDF were bonded additionally with PVAc adhesive. All together 13 series of test samples have been produced at 20 ºC room temperature. For each type of adhesive and substructure were prepared 20 test samples. All the requirements given by the adhesive producers have been met. Test samples have been conditioned for 7 days at 20 ºC and 65 % relative humidity.

Figure 1. Test sample for evaluating the tensile shear strength of glued materials (units: mm)

Figure 2. Test sample for evaluating the tensile shear strength of glued materials

2.3.2. Test method

All tests were carried out on universal testing machine. Tension load was applied to the test specimens (Figure 2). The loading was continued until a non recoverable drop in load occurred.

Ultimate loads were converted to tensile shear strength value by means of the expression

. (1)

where T – tensile shear strength, N/mm2

Fmax – ultimate force, N A – gluing area, mm2 l – length of tested gluing surface, mm b – width of tested gluing surfaces

Additionally the elastic deformation was recorded for each test sample.


52

3. RESULTS AND ANALYSIS

The data from the research carried out to determine tensile shear strength of solid surface materials with different wooden materials and foam PVC boards are processed statistically. In the Table 1 and Figure 3 are shown the results of the test.

Table 1. Statistical data for tensile shear strength of solid surface material with: 1- Sikaflex®-11FC+ and plywood; 2 - Sikaflex®-11FC+ and MDF; 3 - Sikaflex®-11FC+ and laminated PB; 4 - Sikaflex®-11FC+ and PB; 5 - Sikaflex®-11FC+ and foam PVC; 6 - Moment Express Fix and plywood; 7 - Moment Express Fix and laminated PB; 8 - Moment Express Fix and foam PVC

Type of adhesive and material

1 2 3 4 5 6 7 8

Mean value N/mm2 0.99 1.36 1.19 1.23 0.24 4.95 1.96 1.67 Number of test samples

no 16 16 15 15 12 15 17 15

Standard deviation

N/mm2 0.20 0.18 0.21 0.23 0.05 1.03 0.38 0.30

Coefficient of variation

% 19.9 13.4 17.2 18.3 20.3 20.9 19.2 18.0

Max N/mm2 1.30 1.60 1.60 1.50 0.31 6.60 2.80 2.10

Min N/mm2 0.70 1.00 0.90 0.90 0.19 3.90 1.20 1.00

Median N/mm2 1.00 1.30 1.10 1.30 0.22 4.50 1.90 1.70

Results for tensile shear strength for samples bonded with PVAc adhesive are not given

in the data. The reason is that the test method according BDS EN 205 has some disadvantages, especially when good adhesion of the glue is performed. For these test groups shear strength was equal or exceeded shear strength of the wood based or solid surface materials and no significant differences between different bonding conditions can be proofed. Test samples with substructure of MDF and particleboards bonded with rubber based adhesive are also not included because the wood based materials had less strength compared to the bonding line. For both combinations discussed above another type of testing should be used.

One component polyurethane adhesive with a commercial name Sikaflex®-11FC+ shows relatively good bonding strength (tensile shear strength from 0.99 to 1.36 N/mm2), close to the recommended from the manufacturer value of 1.5 N/mm2. The only one exception is for the test samples with foam PVC boars, where the strength is 0.24 N/mm2. For this substructure either a different adhesive or a primer before gluing must be used. The highest strength was observed for test samples made of solid surface and MDF. Based on a t-test the differences between test samples 2 and 4, and 3 and 4 are not significant. With all the other results the differences are statistically significant (p=0.05). The observed way of destroying of the bonding line at this group of test samples showed that less adhesion is achieved with the solid surface material. As it is non porous substance, for better results the surface should be processed with fine abrasive pad. An exception is only the group of foam PVC where the adhesion with solid surface material is higher compared to the PVC.

Rubber based adhesive with a commercial name Moment Express Fix PL 600 gives in generally highest bonding strength compared to the one component adhesive. For the plywood substructure the difference is five times. The same situation is with Foam PVC where the bonding strength is 1.67 N/mm2. For MDF and particleboards bonding strength was higher than the strength of the wood based materials which were destroyed. The highest measured tensile shear strength nearly 5 N/mm2 was observed for the test samples of solid


53

surface and plywood. This corresponds to the recommended from the manufacturer value of 5 N/mm2. This result may be due to a fact that the adherent is solid wood as veneer. All differences are statistically significant (p=0.05).

Figure 3. Tensile shear strength of solid surface materials with different wooden and non-wooden materials: 1- Sikaflex®-11FC+ and plywood; 2 - Sikaflex®-11FC+ and MDF; 3 - Sikaflex®-11FC+ and laminated PB; 4 - Sikaflex®-11FC+ and PB; 5 - Sikaflex®-11FC+ and foam PVC; 6 - Moment Express Fix and plywood; 7 - Moment Express Fix and laminated PB; 8 - Moment Express Fix and foam PVC

Elasticity of the bond line is an important characteristic for the gluing ability of different adhesives to solid surface materials with wood based and non-wood based materials. It is clear visible from the Figure 4 and 5 that one component polyurethane adhesive with commercial name Sikaflex®-11FC+ has higher bond line elasticity. Opposite, the stronger bond line, obtained with rubber based adhesive has lower elasticity. No data has been recorded for PVAc adhesive because for this test groups shear strength were equal or exceeded shear strength of the wood based or solid surface materials.

Figure 4. Deformation of the bond line of test samples bonded with one component polyurethane

adhesive Sikaflex®11FC+

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

1 2 3 4 5 6 7 8

Ten

sile

she

ar s

tren

gth,

N/m

m2

050

100150200250300350400450

-0,5 0,5 1,5 2,5

For

ce F

, N

Deformation ɛ, mm

Sikaflex®-11 FC+ -plywoodSikaflex®-11 FC+ -MDF


54

Figure 5. Deformation of the bond line of test samples bonded with one component rubber based adhesive Moment Express Fix PL 600

This study shows that the investigation on the gluing ability and adhesion strength of

solid surface materials and wood based and non-wood based material with different adhesives put a lot of questions which has to be aim of a further researches in this field. 4. CONCLUSIONS 1. The test results indicated that, in general, all the tested adhesives – one component

polyurethane (Sikaflex® 11 FC+), rubber based (Moment Fix Express) and PVAc (Folco Lit X 3000) are suitable for gluing solid surface materials to wooden materials as decorative elements.

2. For establishing a high strength bond for a structural joint has to be used a combination of plywood and solid surface materials bonded with one component polyurethane (Moment Fix Express) or PVAc adhesives.

3. For better adhesion strength is recommended solid surface material to be bonded with rubber based adhesive to the substructure material made of foam PVC board.

4. One component polyurethane adhesive with a commercial name Sikaflex® 11 FC+ has better elasticity of the bonding line compare to the rubber based tested adhesive.

5. For evaluating the adhesion strength of solid surface materials with wood based materials with PVAc adhesive a test method different to BDS EN 205 should be used.

6. For determination of adhesion strength of solid surface materials with other wood based and non-wood materials BDS EN 205 test method is suitable for adhesives with bonding strength less than 6 N/mm2.

5. REFERENCES ADAMS, R.D.; COMYN, J.; WAKE, W.C. (1997): Structural adhesive joints in engineering. Chapman &

Hall. DUNKY , M. (2003): Adhesives in the wood industry. Handbook of Adhesive Technology, 2.

0

50

100

150

200

250

300

350

400

450

0 0,5 1 1,5 2 2,5

For

ce F

, N

Deformation ɛ, mm

MEF PL 600 - plywood

MEF PL 600 - LPB

MEF PL 600 - FPVC


55

KONNERTH, J.; GINDL , W.; HARM, M.; MÜLLER, U. (2006): Comparing dry bond strength of spruce and beech wood glued with different adhesives by means of scarf-and lap joint testing method. Holz als Roh-und Werkstoff, 64 (4): pp. 269-271.

KYUCHUKOV, G. (2010): Test method of the adhesive strength of solid wood panels. DMT – Design, Materials, Technology, XII, 66, (3): pp. 62-66.

KYUCHUKOV, G.,; KYUCHUKOV, B.; JIVKOV , V.; MARINOVA, A. (2001): Influence of wood species, type of adhesive and the method of testing on the adhesive strength. Proceeding of the XVth International Symposium “Adhesives in Woodworking industry”. Slovakia, Zvolen, 97-100

DUNKY , M., A. PIZZI , M.VAN LEEMPUT: (2002): State of the Art-Report. COST- Action E13, part 1 (working group I, Adhesives), European Commission, Brussels, Belgium.

SERRANO, E. (2004): A numerical study of the shear-strength-predicting capabilities of test specimens for wood–adhesive bonds. International journal of adhesion and adhesives, 24 (1): pp. 23-35.

EN 205:2006 Adhesives – Test methods for wood adhesives for non-structural applications - Determination of tensile shear strength of lap joints.

DU PONT URL:http://www.dupont.co.uk/products-and-services/construction-materials/surface-design-materials/brands/corian-solid-surfaces.html


57

Lathe Tool - It’s Development from the Ancient times to Nowadays

KAMPERIDOU Vasilikia*– BARBOUTIS Ioannisa a Aristotle University of Thessaloniki, Faculty of Forestry and Natural Environment, Laboratory of Wood

Products and Furniture Technology, Thessaloniki, Greece *Corresponding author: [email protected]

Abstract - One of the most important wood processing machines from ancient times till our times is the lathe. The tool of lathe occupies a prime position in the group of wood cutting machine tools and is a valuable invention for human mankind, since it offered the possibility of constructing a huge variety of objects and surfaces. The specific work indulges in the history of the lathe, the progress and evolution of this tool from the past time to the present. Additionally, the construction and operation of the lathe is analysed, presenting also some general information on lathes, the key components, types of lathes, the main turning types, the cutting tools and the tool holder’s axis of the lathe and how some of them changed through the years.

CNC / lathe / revolver lathe / tool / turning / wood processing 1. INTRODUCTION

Over the centuries, mankind has recorded very significant progress, part of which was the development of a range of tools and machines that contribute to the use of different materials, such as wood, metal, etc. satisfying in that way several human needs. For the treatment of materials and the production of various products, various tools were devised and implemented in machines, using energy to achieve the work with much less effort and time.

Such tools are mainly used in the treatment of materials (wood, metal, etc.) in such a way as to obtain the desired configuration of shapes, forms and dimensions, by means of material removal. Apart from the conventional tools that work manually, now there are also automatic tools (CNC, NC, etc.) connected to a computer, which are characterized by accuracy and clearly greater efficiency. There are several tools which work by removing material, such as “cutting” machine tools, that basically cut the raw material into smaller pieces or cut shaped pieces of the material, in order to avoid creating much waste during the process, while the material is being transformed into an accomplished in form and dimensions product. Also, in recent years, there is a confluence of several separate machines that work on a production line or a flexible machining system.

The lathe occupies an important position in the group of cutting tools and a valuable invention for humans, since it offers the possibility of constructing a huge variety of objects and surfaces. The specific work indulges in the history of the lathe, the progress and evolution of this tool from the past time to the present. Additionally, the construction and operation of the lathe is analysed, presenting also some general information on lathes, the key components, types of lathes, the main turning types, the cutting tools of the lathe and how some of them have changed through the years. 2. HISTORY OF LATHE

Lathe is one of the first tools used and very useful to mankind, even nowadays that the technology has been recorded a great progress (STEEDS, 1964). The lathe took its name by the prefix «τορ-» («tor»), which comes from the verb «τείρω» («tiro»), which means rub (or chagrin intensively) and the suffix «-νος» («nos»), and basically, it is a tool built with the


58

intention of formulating a material through the clamping and rotation of the force under appropriate cutting means.

The operation of the lathe is based on a very simple and understandable principle. Wood is forced to rotate on an axis, while a sharp tool cuts, scrapes or smoother it, in order to give the final shape to the product. The wooden element is fastened at two points, which form the axis of rotation (STEEDS, 1964). This simple machine, the machine of lathe, is used for thousands of years and some of the reasons are listed below. Essentially, with pretty much ease, lathe produces objects of round surface, it is a machine of inestimable value and contribution to the construction of wheels for carriages, windmills or pumps. With the help of the lathe, rotating spindles are easily assembled in structures of high complexity, such as chairs, tables, beds and other furniture. From an aesthetic standpoint, the lathe helps in creating aesthetic, decorative objects and surfaces, which would be impossible to be constructed without the use of lathe. Combining simplicity in engineering, adaptability, and high aesthetics, turning has been proven to be a valuable practice adopted and strongly requested by the market, while it is part of the European culture (RETTIE, 2009).

The invention of the lathe is placed in the ancient times. More specifically, it was initially known to the Egyptians, and some years later on the Syrians, Greeks, Romans and later throughout all the Byzantine Empire. One of the earliest depictions of lathe was the fresco found in Ptolemaic dynasty tomb. In those years, the lathe was also known by other names, derived from the turbulence and rotation or the material removal, while later people began to use the word "tearing" as the name of the lathe. Several sources indicate that the tool of lathe was used since 1300 BC by the Egyptians. Also in the work of Herodotus the use of the lathe in pottery is reported, demonstrating the fact that they had already known and used the lathe, but as evidenced by scholars such as for example, by Varoufakis, who studied the crater of Derveni, the lathe of metal objects seems to be used already those years. The type of “arched” lathe depicted in the images that follow, was a revolutionary discovery of those ancient times, since for the first time only one craftsman was enabled to handle the lathe, while the earlier lathes required definitely two craftsmen. These earliest forms of lathe were the vestibule of the evolution of the lathe, and the mechanical evolution in general (NOESIS, 2012).

A. B.

Figure 1. A., B. Arched lathe (http://www.archimedesclock.gr/gr/kataskeves/diafora/tornos.html)

The lathe was also used by craftsmen who made pulleys, gaskets, carriages, connectors, copper utensils, anvils, bells, etc. From 4th to 7th century, there is evidence that show the lathe in England, while in 1180 according to data the first turner guild was established in Cologne (Germany) (RETTIE, 2009). In the Middle Ages, European turners seem to prefer a kind of lathe called "Spring" lathe. In this form of lathe, there is a frame of sufficient height in order the turner to stand comfortably in it, which holds tightly the fixed element and rotates it between two points of an axis, fixed on two sharp metal parts that otherwise are also called centres. There is a string that runs all the way from the tip of the pole, to the base, so as to take easily place the phenomenon of recoil, necessary for the rotation of the wooden piece. The string is well fastened around the piece that is going to be turned, at the point where exactly it is needed to be turned, in order the piece to be drifted by the string as it moves, while the string ends in this kind of a pedal (or pedals) located at the lowest point the lathe. At


59

this point where the operator applies his leg, he causes the movement, while as the operator leaves the pedal, the movement is released. Simultaneously, the operator apply to the surface of the wooden element, knives and other cutting tools, in order to give the appropriate shape and dimensions to the material (http://www.historicgames.com/lathes/springpole.html).

The string lathe has been proven to be of particularly high adaptability. It is lightweight and portable, two very important factors for manufacturers of that time, who may be moved and travelled to places where raw materials were in abundance. That lathe was also easy to be manufactured, and most of the necessary for its construction parts, were easy enough to be fixed by the manufacturer himself. The main drawback mainly derived from the design of this lathe was its relatively low speed, and the limitations in size and weight of the wooden object that was going to be turned. Until the mid 19th century, despite these limitations, the lathe that uses string remained the most popular among other types of lathe, and was preferred mainly by chair and various artefacts manufacturers (RETTIE, 2009).

a) b) c)

Figure 2. a) foot spring lathe, b)hydrokinetic turning (1425-1523), c) lathe with band (UOC)

Many variations of this lathe design followed, incorporating also a lever (handle), in order to replace the specific frame that was situated above the head of the operator, with a frame on the basis of the tool or with a bow that holds the string and converts the whole process, to produce a constant rotational movement, providing greater convenience to the operator (RETTIE, 2009).

In the late 15th and early 16th century, the point of cutting tools deposition as the turning object was rotating appeared for the first time in lathes of that time. This added surface was based on pins, as is shown in figure 3, and the surface is fixed in the desired angle using some wedges, in a way that the cutting tools can rely on a stable surface to achieve greater accuracy during turning and secondly, to increase the possibilities of turning and range of turned surfaces that could be achieved.

The most popular lathe used in the Middle Ages was the “spring” lathe. One of the main achievements in the operation of the lathe was the passage of the back and forth motion in continuous rotational movement, which ensure faster rotation, while giving the possibility of processing parts of much larger dimensions. In addition, the design and construction of this lathe, reduced the effort and energy consumed by the turner. As evidenced, from the Middle Ages, it was known how to converse the reverse movement into a rotational movement. With the help of some mills that were taking advantage of the running water movement, the motion was transferred using some arms, to reciprocating saws, giving a continuous rotary motion. Over the years, the mechanical skills of craftsmen were further developed and the complexity of the mechanisms as well, which was often increasing the cost of these structures and machines. To sum up, initially, the first lathes that appeared were moving with the power of man muscles (foot turning), and then with the help of water movement (hydrokinetic turning), referring to downstream mills and finally the motorized turning lathes (UOC, 2012).

Some lathe designs have been found also in sketches of Leonardo da Vinci, who besides having captured, is likely to have also improved some of these lathe designs that have already existed. The existence of continuous rotational motion lathes was set in from 1560 to 1570 and was often depicted in books ("Book of Trades" by JOST AMMAN , etc.).


60

B. C.

Figure 3. a) Lathe continuous rotary motion bearing burin (Archive of Samian Folklore, 2008), b), c) Furniture and objects which required turning for their construction

The use of these lathes of the continuous rotation was quite limited in those years, mainly

due to higher costs, the abundance of older lathes of reverse motion, and probably, due to the restrictions that were being raised by the trade unions of that era. More specifically, the urban trade unions set often restrictions on the use of specific tools or methods used by themselves as craftsmen. For the lathe, in particular, there have been many conflicts over who has the right to use it, while the regime that tried to establish a situation where one had to have a special permission in order to be able to use the lathe was not preceded. In the countryside, the restrictions were not so intense and craftsmen could trade lathes and use their own tools.

There were many furniture pieces and small objects that required turning during their construction, as well as various connections of wooden or metal components such as the most frequently used type of connection "Mortise and Tenon" (Figures 3 b and c).

The lathe operator undertook mainly indoor furniture, and one of the most popular furniture manufactured with lathe was the tripod stool (Figure 3 b), which is a highly stable cabinet formed after connecting wooden pieces of cylindrical section. It used to adorn the homes of both villagers and wealthy families (nobles, clergy, scholars, etc.) and many images of this furniture have been recorded dating from the early 16th century onwards. Various elaborate versions of this turned furniture followed, while the following years back and also slots for elbows were added to the furniture, giving an integrated chair (17th century). Except furniture, plenty of other objects were being manufactured using lathe, such as wind, mortar, mugs, cups, plates, tool handles, castors, trolley wheels, boxes, sieves, various games, pulleys, buttons, cuffs, scales, pumps etc.

The artisans of lathe in the Middle Ages were using a variety of wood species, and based on found Anglo-Saxon and Scandinavian artefacts (ca. 990-1000 AD), it has been proved that maple, birch, walnut and ash were the wood species chosen more often, while yew, pixos, beech, and the black pine were used under certain conditions. As it is known, each wood species has different physical and mechanical properties, and therefore, its behaviour during machining can greatly vary. Generally, denser wood achieves better results, better turning and smoother surfaces. The oak, for instance, although was routinely used in furniture wooden joints construction, as it was demonstrated after some years, it is not easily machined, due to the structure and layout of the annual rings, therefore it was abandoned.

In Middle Ages, the turners worked mainly with non-conditioned wood, of high humidity. The cause of using wet wood during turning is that the humidity makes the wood softer, which is more easily cut and thus, the operation of lathe is better. As the wood fibres are soft and flexible, the technician applies the gouge in rotating piece, removing material as a continuous wooden strip. Of course, the wet timber is not suitable, when the machining should be done internally, which means on the inner side of the object, a cavity, for example in glasses, cups etc. The reason is that when the timber starts to dry, different dimensional changes in the transverse, radial and tangential direction of wood will be caused, which will lead to deformation or breakage of the structure. The timber can be machined wet, but during the connection of the pieces and the construction of the wood product is necessary wood to be dry (10-12 % moisture) (RETTIE, 2009). As LEON BATTISTA ALBERTI also reports, during the


61

15th century, turners used to immerse the timber in water before the use and often leave covered with mud for 30 days in order to facilitate its handling, contributing to a more stable material and avoiding checks and distortions of wood (RETTIE, 2009).

It is striking that some researchers report that the history of modern mechanics starts in the last years of the 18th century, when Henry Maudslay, of English origin, produces the first lathe which created thread, generating the known screw. Clearly, if one compares the 18th century lathe, to today's lathes, he would undoubtedly conclude that the lathes of that era were very time consuming, laborious and of low accuracy, but it was of great significance that that tool was developed in the lathe that we know today (BURGHARDT et al., 1959).

3. THE BASIC COMPONENTS OF LATHE TOOL

The lathe is a machine tool used in the construction of objects of circular cross section, as mentioned above. The main movements during turning up of the main motion are the rotary motion of the object and the feed motion of the cutting tool which is rectilinear (BURGHARDT et al. 1959). Some of the most important pieces of a common machinist lathe are the lathe bed (on the lathe), the electric motor, headstock and propulsion, or turning area with predetermined dimensions (diameter, turning length), the tool axis or the centre line/ tailstock, the drive threading axis, feed or propulsion axis and sleeve axis (PARIKOU, 1988). The tool of lathe can yield rotational, curved, concave or flat surfaces.

a) b)

Figure 4. a) The basic parts of a lathe: a. lathe bed, b. headstock, c. tool axis, d. tailstock, e. feed gear box, f. drive threading axis or lead screw, g. feed or propulsion axis, h. switch bar, b) Turning

and the motions carried out (UOC) One of the most basic parts of the lathe is the lathe bed, which is based on two pedestals

together via a very strong beam. The lathe bed features in the upper flat slides or prisms, which should be in perfect alignment and highly resistant to corrosion. During the turning, as mentioned previously, a rotational movement is performed around the axis of the wood, while the tool is displaced continuously linearly parallel to the axis of the piece until the desired shape of wood is achieved. This longitudinal turning can be internal or external of the material. Apart from this longitudinal turning, it is possible to have a frontal, collateral, lateral, conical, spherical, curved turning and the corresponding surfaces, and also threading, grooving, cutting of shoulder nerve etc. (PARIKOU, 1988).


62

a) b) c) d)

e) f) g)

h) i) j)

Figure 5. Types of turning treatments: a) external longitudinal, b) internal longitudinal, c) external transversal, d) internal transversal, e) external taper/conical, f) internal taper/conical, g)

external profile, h) internal profile, i) external thread, j) internal thread (UOC)

A lathe of general uses can implement the following basic turning types: Turning external and internal cylindrical surfaces, turning of flat surfaces / transverse turning, turning of conical surfaces, boring small or deep holes, eccentric turning (cams, crank shafts), turning of specific shape / profile, cutting internal or external threads of all forms, treatment of external and internal spherical surfaces, making winding of springs knurling etc., sanding onto lathe bed, grooving and cutting.

At the left edge of the bed, there is the gearbox, with the necessary number of gear means / clutches, necessary for the transmission of the rotational speed to the spindle motor. The alongside and transversely promotional moves are achieved through the tool axis, which comprises the longitudinal, the transverse slide and the slide of the rotating plate. All the cutting tools are fixed in a tool holder, which is located in front of the bed (tool carrier box) and run along slides. The movement of tool axis is accomplished either manually with the help of the lever, through a rotation which press the gear wheel engaging with a toothed rack fixed to the bed or automatically through the rotating axis, the propulsion axis, while for threads cutting, respectively it is accomplished through a threading axis (PARIKOU, 1988). 4. CONSTRUCTION AND FUNCTION OF LATHE

While the pieces of circular cross section rotate around their axis in lathe machine,

various types of cutting tools are applied on the surface, forming the desired design. Undoubtedly, the range of patterns that may be achieved is very wide (BURGHARDT et al. 1959). The cutting tools may be held by the operator and the machine to be driven in an appropriate manner by him or they may be applied to the moving element tool axis carrying the selected tool and then the operator just drive the entire system. Of great importance is the stabilization of the piece that is going to be turned, in order to avoid accidents and destruction of wood.

There are lathes of various sizes depending on the dimensions of the treated material. It is very important the placement of the lathe at a suitable height, and the stabilization of a solid substrate, in order the turning process to be convenient and safe for the operator (ERNEST, 1980). A lathe of acceptable quality usually has an engine of ¾ or 1 horsepower capacity. Most lathes are capable of switching 3 or 4 different speeds. Higher accuracy and purity are usually achieved at higher speeds. Initially, when the material is still completely raw the speed is kept rather low, while the material is shaped as the speed rises. Additionally, the heavier and denser wood we have, the lower speed should be applied (ERNEST, 1980). The cutting motion that is carried out by the rotation of the object is called cutting speed (Vc) (MANTEMIS, 1996). There are lathe beds that give approximate values of cutting speed for each material and diameter of the object. Upon the engine of lathe one can usually find a


63

fixed chart to read the speed n with which the lathe operates, while there is also the possibility of calculating the speed through beds, putting the cutting speed and wood element diameter one can find the respective speed of the lathe (MANTEMIS, 1996). The cutting speed or as it is called otherwise, the speed of rotation of the turned wooden piece and the speed of propulsion which is also called movement of the tool in a direction parallel with the axis of wood, depend mainly on the nature of the treated material, the material that the tool is made of, and the desired quality of wood surface one wants to achieve (MANTEMIS, 1996). In planning treatment, usually a large propulsion and cut depth is adopted, while in treatments where great attention is crucial for the final result, such as the finishing treatment, usually small cutting depth and propulsion is selected. Referring to propulsion, essentially one means to the movement that the tool completes (in millimetres) in one rotation and is selected according to the engine power and the desired final surface quality.

Cleaning the lathe is a very important and necessary process and should be take place when the lathe is idle. A small piece of cloth soaked in kerosene, can be used to remove dirt and oils, while the surfaces should be passed with a dry cloth in order to remove residual of kerosene. The quiet running bearings should be lubricated each time before use, with the necessary quantity of oil and checking of pipes that lead the oil in different parts of the machine should be frequent, in order to avoid their blocking (BURGHARDT et al., 1959).

The number of shapes and kinds of cutting devices used in lathe is quite large, despite the efforts that have been made in the direction of standardization of these cutting tools and thus reduction in their number (STEEDS, 1964). Very important is the form of the waste coming from the cutting tool and tool material and its resistance to wear and tear. The hardness of the tool should be maintained even at high temperatures, in order to prevent the occurrence of cracks (MANTEMIS, 1996). The tools are typically made of steel (either pure steel, or alloys), a very durable material which is sufficiently elastic and resistant at high temperatures (400-600 oC). Tools are usually coated with titanium nitride to withstand even more to wear.

5. LATHE TYPES The tool of lathe, following the general technological development has been evolved and

has met all the requirements of structures characterized by accuracy, productivity and automation. Those three factors are essential in each tool for high volume production, good quality product and low cost. In terms of use, the lathes are divided into lathes of general use and lathes of special purposes.

In the lathe of general use, almost all turning processes can take place. There is the potential to receive wooden items between the centres and for this reason, this lathe is also called "lathe of the centres". These lathes are usually equipped with mechanical motion for propulsion and therefore, are often called "propulsion spindle lathe" (MANTEMIS, 1996). In this category of lathes is also included the “centre-line parallel” lathes, or “universal”, (equipped with propulsion axis and screw threads), the “centre-line parallel productive” lathes (equipped only with a propulsion axis or a hydraulic transmission of propulsion), “parallel” with a variety of knives, “rotational” or “revolver” lathes, the “copying” lathe, the “semi-automatic” and “automatic”, “vertical” and “frontal” lathe.

The “revolver” lathe, referring to the facilities it offers, lies between the “universal” lathe, that all operations are driven by the craftsman and the completely “automatic” lathe. The automatic lathe operates either with a purely mechanical program of automation, or by an electronic control unit (NC or CNC). The “revolver” lathe is characterized as "semi-automatic machine", used mainly where there is a relatively large production. In this way, in a wide variety of products, the “revolver” lathe performs the same work in much shorter time, compared to the conventional lathe, while the accuracy achieved is quite the same.


64

Called also as "expertised" or "sectoral”, lathes of special purposes are used in specific processing and turning of objects in various industries. For example, lathes for cutting threads, lathes of the automotive industry, lathes machining crankshafts, lathes in the railway etc. The classification of lathes in this category depends on the use, the characteristic structural dimensions and different sizes.

6. CONCLUSIONS Taking all the above into account, turning can provide various forms of the work piece

through the combination of various movements, and use of appropriate cutting tools. Apart from conventional lathes, which are guided by the operator who makes all the necessary movements and arrangements for the treatment, lathes can also be driven digitally and in this way the movements and settings require much less human involvement since the electronic guidance unit and the developer undertake all the main work. In conclusion, it could be mentioned that the lathe is one of the emerging tools used during the evolution of humanity, has been a valuable tool over the years, enabling the production of a huge variety of surfaces and objects of high quality, usability and aesthetics. Through the years, several features of lathe machine have been changed and improved, providing greater precision in dimensions and shape of the wooden elements, higher machine efficiency, higher production speeds, ease of machining, and less effort and risk of accidents for the operator of lathe. 7. REFERENCES

BURGHARDT, H.; AXELROD, A.; ANDERSON, J. (1959): Machine Tool Operation – Part 1: Safety,

Measuring Tools, Bench work, Drill Press, Lathe, Forge work. McGRAW – HILL BOOK COMPANY, ISBN 07-008961-2.

ERNEST, S. (1980): The Mitchell Beazley encyclopaedia of Working in wood. Mitchell Beazley Publishers Limited. ISBN 0855332905.

MANTEMIS, S. (1996): Tool machines I. Library mechanical engineering. European technological Publishing - G. & S. Parikou & Co., ISBN 960-331-132-4.

ΝOESIS (2012): Ancient Greek Technology. Thessaloniki Science Center & Technology Museum. URL: http://www.tmth.edu.gr/aet/thematic_areas/p527.html.

PARIKOU, G.Ι. (1988): Machining Technology. Publishing ΙΩΝ. ISBN 960-405-076-1. POLLACK , H.W. (1976): Tool design. Reston Publishing Company, Inc. ISBN 0-87909-840-6. PREFECTURE OF SAMOS (2008): Photo Archive of Samian Folklore,

URL: http://culture.samos.gr/c/portal_public/ RETTIE, I. (2009): Lathes Part 1: About Medieval and Renaissance Lathes.

URL:http://www.bloodandsawdust.com/Blood_and_Sawdust/Lathes_Part_1__About_Medieval_and_Renaissance_Lathes.html.

STEEDS, W. (1964): Engineering Materials Machine Tools and Processes. Longman Group LTD, London, ISBN 0582427290.

UOC, TECHNICAL UNIVERSITY OF CRETE (2012): Class textbook. Polytechnic Faculty of Crete, Laboratory of Micromechanics and Structures.


65

Design and Manufacturing of Organic Shape Furniture

KITEK KUZMAN Manjaa – ŠERNEK Milana – KARIŽ Mirkoa* a Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana, Ljubljana,

Slovenia *Corresponding author: [email protected]

Abstract – Wooden furniture of organic shapes was mostly handmade in the past, each piece was almost unique, since the manufacturing processes did not allow repeatability and larger quantity production of the same products. Today, modern 3D modelling software leads to completely different prospective in wooden furniture design and production. It enables modelling of any kind of shape, based on ideas, natural shapes, even 3D scanned existing shapes, etc. Furthermore, prototypes can be 3D printed. This enables that visual presentation of designed form is made in real. Based on the printed forms virtual models can be improved leading to the final sophisticated model. Additionally, during design process the best construction details can be made to improve material efficiency and manufacturing time. Final product can be than made on CNC machines, enabling reproduction of the same product of desired shape in chosen quantities.

furniture design / 3D modelling / tectonic of timber architecture 1. INTRODUCTION

1.1. Organic design

Organic architecture is a philosophy of architecture which promotes harmony between human habitation and the natural world through design approaches so sympathetic and well integrated with its site, that buildings, furnishings, and surroundings become part of a unified, interrelated composition. Organic architecture is a term Frank Lloyd Wright used to describe his approach to architectural design. The philosophy grew from the ideas of Frank Lloyd Wright's mentor, Louis Sullivan, who believed that "form follows function." Wright argued that "form and function are one." PEARSON (2001) describes organic design as design inspired by nature and sustainability, health, conserving, and diverse, unfold, like an organism, from the seed within. It follows the flows and is flexible and adaptable. It also satisfies social, physical, and spiritual needs, grows out of the site" and is unique. It celebrates the spirit of youth, play and surprise and expresses the rhythm of music and the power of dance. The art of deploying construction technology in such a way that it forms an integral component of the design and actively helps to shape it is what KENNETH FRAMPTON (1995) defines as tectonics.

With the inspiration coming from the wood itself is the aim to offer a wide selection of live edge wood furniture boasting organic shapes and natural flaws that add to the innate beauty and sensory experience. The easy machinability of wood makes it an ideal material for digitally controlled processing. For this reason, the timber industry is well equipped with such machinery, and timber is taking on the status of a high-tech material (BURI – WEINAND, 2011, 2012) (Figure 1).

Figure 1. The tectonics of timber architecture in the digital age (folding, bending, weaving)


66

1.2. The tectonics of digitally designed timber furniture: the organic forms in wood

It is possible to show how parametric design tools can be created that are specifically tailored to timber and its material properties. Tectonics – the interplay of architectural expression, efficiency and the construction of support timber structures – is one of the focuses of our research and teaching at the Department of Wood Science and Technology at the University of Ljubljana.

New wood based materials (liquefied wood, modified wood, densified wood) and processing technologies along with the new possibilities for depicting and calculating support structures play an important role here. The aim is an efficient interlinking of design and construction that integrates the architectural, support-structure-related and production requirements, leading to sustainable and high-quality solutions (Figure 2).

Figure 2. The tectonics of timber architecture as reflected in its production conditions 1.3. Furniture and production conditions

The life cycles of products are becoming increasingly shorter, leading to an increasing need for intensified development of new products or updating the existing ones. Computer-aided manufacturing (CAM), in which computer-aided design (CAD) and computer numerically controlled (CNC) machining are integrated for the production of parts, became a viable option for the woodworking industry in the 1980s (WIEDENBECK – PARSONS, 2010) and is one of the possibilities for reducing design and development time for new products. In modern furniture industry, CNC working centres are widely used, especially when high quality of product and flexibility of manufacturing process are expected (GAWRONSKI, 2012).

The new technologies have had great effect on the professions devoted to three-dimensional design work. Processes like modelling, performing basic stress and deformation analysis, and even the production of rapid prototypes can be currently done by a single designer without any need for a range of specialist. Therefore, an experienced designer can be more effectively involved in any design decision. Virtual simulation of product enables designing of optimal design solutions (MIJOVIĆ et al., 2006). 2. CASE STUDY

The information dictating the form of a work piece, which the human previously provided through a one-time machine setting, is now directly integrated into the machine. The information flow from the control program is variable, meaning that components of various shapes can be manufactured without any time losses in production.

The idea of the case study was to design wooden sitting element / chair based on existing organic shape. The basic form for design was simple river stone (Figure 3). The aim of this study was to use available modern 3D modelling software to model the furniture (prototype) and make it with CNC router.


67

Figure 3. Simple river stone

First the photo of river stone was taken from each side (top, front and left view). The

photos were then imported into SolidWorks software, which was used to model our stone. SolidWorks 3D CAD solutions enable quick transformation of new ideas into great products. SolidWorks solutions cover all aspects of product development process with a seamless, integrated workflow-design, verification, sustainable design, communication and data management. Designers and engineers can span multiple disciplines with ease, shortening the design cycle, increasing productivity and delivering innovative products to market faster. Silhouette of the stone was drawn based on these photos (Figure 4).

Figure 4. Silhouette of the stone (modelling with SolidWorks)

The model of the stone was then made with Surface loft. This was initial, base form,

which was the starting point for further design of furniture. Several models were then made with different seating surfaces and dimensions. Bottom part of stone was flattened to ensure stability of stone. Also upper part of stone - a seat was ergonomically designed to fit the contours of the body (Figure 5).

Figure 5. Different model designs

For better visualisation of selected models 3D printing technique was used to make rapid

prototypes. "Experience rapid prototyping" enables design team members, users and clients to gain first-hand appreciation of existing or future conditions through active engagement with prototypes. We illustrate the value of such prototypes in four critical design activities:


68

understanding existing experiences, exploring design ideas, in communicating design concepts and to improve the information required to successfully market a new design. 3D printer ZPrinter 450 was used to make models of selected shapes (Figure 6).

Figure 6. 3D printed prototype M 1:5

For final production the most efficient process was tried to find. It was decided that CNC

router will be used to carve the surface of the furniture. Choice between several options was made - to make it from larger block of wood- half of the stone, or to slice the model to several slices and curve each slice individually and then assemble these slices into final product (Figure 7).

Figure 7. Sliced model

It was determined to make model from larger blocks of wood - half of stone, because that was easier for machine operator- only two longer CNC programs had to be made (one for each half) instead of several short programs for each thin slice of product. The main cost for production of the stone was CNC machining so reduction of time for CNC machining was tried.

Also optimisation of material efficiency was needed, and first idea was to made solid block of wood by bonding lamellas. This could be easier to do, but a lot of material would be wasted and also the product would be much heavier. So it was decided to make frame of wood, which than was bonded into block, so that the block was hollow (Figure 8). This reduced the material consumption and also made the product lighter. So the volume of used wood was only 0.12 m3.

Figure 8. Frames of wood bonded into block


69

Selected finished 3d model was than exported from SolidWorks to AlphaCAM software, which was used to make a program for CNC router. 5-axis CNC machining centre was used to carve product.

Figure 9. 5-axis CNC machining centre and products

3. CONCLUSIONS

An efficient interlinking of design and construction that integrates the architectural,

support-structure-related and production requirements, is leading to sustainable and high-quality solutions. New organic design is a manifesto for wooden furniture of organic shapes in a way that is both aesthetically pleasing and kinder to the environment. It illuminates key themes of organic architects, their sources of inspiration, the roots and concepts behind the style, and the environmental challenges to be met.

Today there is a response to a new age of information and ecology; architects and designers are seeking to change the relationship between products and the natural environment. Students can also experience prototyping's impact on design, working exactly like professional designers and engineers. This project gave them the rigorous ground-level education they need to develop strong backgrounds in science and engineering. They extended existing 3D modelling knowledge with technologies like 3D printing and CNC routing. Acknowledgements: The authors wish to thank the Slovenian Research Agency (ARRS) in the frame of research programme P4-0015-0481. 4. REFERENCES BURI, H.U.; WEINAND, Y. (2011): The Tectonics of Timber Architecture in the Digital Age. In:

Building with Timber Paths into the Future, Munich, Germany: Prestel Verlag, pp. 56-63. BURI, H.U.; WEINAND, Y. (2012): Holz - Tektonik – Digital. In Bau-Netz pdf Magasin. 253. FRAMPTON, K. (1995): Studies in Tectonic Culture. The Poetics of Construction in Nineteenth and

Twentieth Century Architecture, Cambridge, MA. GAWRONSKI, T. (2012): Optimisation of CNC routing operations of wooden furniture parts. The

International Journal of Advanced Manufacturing Technology. DOI 10.1007/s00170-012-4647-5. 67: pp.2259-2267.

MIJOVIĆ, B.; GRBAC, I.; DOMLJAN D. (2006): 3D geometrijsko modeliranje namještaja. Drvna industrija 57 (1): pp. 19-27.

PEARSON, D. (2001): The Breaking Wave: New Organic Architecture (Stroud: Gaia), pp. 72. WIEEDENBECK. J.; PARSONS. J. (2010): Digital technology use by companies in the furniture, cabinet,

architectural millwork, and related industries. Forest Prod. J. 60 (1): pp.78-85.


71

Importance of Botanical Binominal Nomenclature for Hydrothermal Wood Processing

KLARIĆ Miljenkoa – PERVAN Stjepana*

a Department of Material Technologies, Wood Technology Section, Faculty of Forestry, University of Zagreb, Zagreb, Croatia


Abstract – This research paper reports on importance of botanical binominal nomenclature for wood trade and its influence on wood processing, especially on hydrothermal wood processing. Introduction to the basics of botanical binominal nomenclature is made in accordance with latest changes in International Code of Nomenclature for Algae, Fungi, and Plants (MELBOURNE CODE, 2012). The usefulness of knowledge about scientific names of wood species for manufacturers and end users is discussed. Some examples of wood drying defects that can occur due to lack of knowledge on specific wood specie scientific name are shown and elaborated. Also, a several wood species diversity comparison within the same genus related to the hydrothermal processing has been made.

botanical binominal nomenclature / hydrothermal wood processing / defects 1. INTRODUCTION

Nowadays, in the times of globalization the lumber trade does not distinguish national boundaries and has no transportation limitations. Consequentially lumber harvested in North America or Africa can easily be shipped and processed in Europe or Asia and vice versa, respectively final wood products can easily be transported from a continent to a continent in relatively short period of time from producer to a potential buyer. With such international wood trade possibilities, difficulties emerge easily especially if trading parties are not adequately trained and have no necessary knowledge in terms of wood properties and handling. The situation which occurs easily is that the customer get wood product of a wood specie that was not initially declared, and in such cases, those products are usually made out of cheaper wood types (not necessarily worse one). ROSS et al. (2005) pointed out that the name of the wood specie from which the final product is made influences customer choice, and that there is a discrepancy between the valuation of products based on appearance and on the name of wood type. In general it is not considered to be a problem if the aesthetic characteristics of wood products are as the customer expected, and what are the affinities of customer. Still customer will probably pay higher price for the cheaper wood specie. KLARIĆ et al. (2012) stated that furniture manufacturers could in that way, by using commercially less interesting, rarely used, and less expensive species of wood in the production of final products introduce new trends and maximize profits. These wood species are cheaper, which allows the final products of lower cost but with the same level of profit. Such action is acceptable if the customer has also benefited in a way that the final product is slightly cheaper. A more significant problem with the lack of knowledge of specific wood species is emerging during hydrothermal wood processing. Because of the great influence of knowing correct specie, and thereby knowing the scientific name of wood species, imposes a need for basic knowledge of plant systematics, thereby taxonomy and most important botanical binominal nomenclature. Therefore, in this research paper an introduction to basics of systematics and botanical binominal nomenclature are presented along with its influences on hydrothermal wood processing. Wherein, some specific examples associated to the article topic are elaborated.


72

2. PLANT SYSTEMATICS AND TAXONOMY

Systematics and taxonomy are terms that are often mixed with each other, and often used as synonyms. There is a great number of various definitions of systematics. In general, systematics is the scientific study of organisms biodiversity and its interrelationships through revelation of the evolutionary history, while plant taxonomy means classification of plants following certain rules, principles and procedures. The main subjects of taxonomy study are taxa, which are on principle delimited groups of organisms. In generally systematics is term that is more inclusive and encompasses traditional taxonomy. Besides it encompasses taxonomy whose main components are Description, Identification, Nomenclature, and Classification (DINC), its primary goal is the reconstruction of phylogeny, or evolutionary history.

Figure 1. Areas of systematics according to STUESSY (1979, 2009)

Phylogeny is a study of genealogy and evolutionary history of a taxonomic group (SINGH,

2010). Usually it is presented in the form of a cladogram or phylogram (Figure 2), which visualize the evolutionary pattern of decent through branching diagram. The basic difference between cladogram and phylogram is that the phylogram indicates the degree of relationship between organisms based upon similarities and differences in their characteristics trough the distance among them (branches lengths). Respectively phylogram corresponds more closely to the real elapsed time. As mentioned above, for systematics and taxonomy, cladogram or phylogram are terms that are also frequently mixed.

Figure 2. Cladogram of the woody and seed plants (source: SIMPSON, 2010)


73

2.1. Botanical binominal nomenclature

Botanical binominal nomenclature is encompassed by taxonomy and it deals with the determination and assignment of a correct name for taxa (singular: taxon) or a taxonomic group. In generally, for different groups of living organisms, there are different rules. Formal international rules, criteria and recommendations according to which naming plants (including Algae and Fungi) is based on International Code of Nomenclature or ICN (MCNEILL et al., 2012) published by the international Association of Plant Taxonomy (IAPT). International code is updated approximately every six years at each international Botanical Congress, therefore, before 2012. it was International Code of Botanical Nomenclature or ICBN (WIENA CODE). ICN is governed according to six principles. The fundamental principle of nomenclature is that each taxon, whether species, genus, etc., can bear only one correct name in order to avoid confusion. In accordance with the above mentioned, the name assigned to individual plant is known as scientific name of the plant and it is binominal, consisting of the genus name and the specific epithet, which are treated as Latin. Casper Bauhin (1623) introduced the concept of Binominal nomenclature, but he did not use it. Firmly established system of naming was set forth by Carolus Linnaeus in his Species planetarum (1753), while early rules of nomenclature were set in his Critica botanica (1737), and further amplified in Philosophica botanica (1751) (SINGH, 2010). Taxa ranks are hierarchically arranged by the system of nomenclature. Taxa ranks in descending sequence are given in Table 1, while the seven major obligatory ranks are bolded.

Table 1. Taxa ranks for plants in descending sequence according to International Code of Nomenclature (MCNEILL et al., 2012).

TAXONOMIC RANKS OF PLANTS Abbreviation Ending latin english Regnum Kingdom - various Subregnum Subkingdom - various Phylum [or Divisio] Phylum [or Division] - -phyta Subphylum [or Subdivisio] Subphylum [or Subdivision] - -phytina Classis Class [cl.] -opsida Subclassis Subclass [subcl.] -idae Ordo Order [ord.] -ales Subordo Suborder [subord.] -ineae Familia Family [fam.] -aceae Subfamilia Subfssamily [subfam.] -oideae Tribus Tribe [tr.] -eae Subtribus Subtribe [subtr.] -inae Genus Genus [gen.] various Subgenus Subgenus [subg.] various Sectio Section [sect.] various Subsectio Subsection [subsect.] various Series Series [ser.] various Subseries Subseries [subser.] various Species Species [sp.] various Subspecies Subspecies [subsp.] various Varietas Variety [var.] various Subvarietas Subvariety [subvar.] various Forma Form [f.] various Subforma Subform [subf.] various


74

3. HYDROTHERMAL WOOD PROCESSING

Angiosperms are higher evolved group of plants than the gymnosperms are, more precisely conifers. Higher evolutionary development in particular means that angiosperms have a more complex histological structure. Because of the different histological structure, the angiosperms are more difficult to dry than gymnosperms. As it was mentioned, there is a significant difference in histological structure between hardwoods and softwoods, and they behave differently during kiln drying process. Therefore, hardwood species cannot be easily dried like softwoods, the drying time is significantly prolonged and the occurrence of defects is more frequent. There is not just the difference between hardwoods and softwoods but among each other aswell. The slight difference exists even among the same wood specie.

Hydrothermal treatment of wood is a crucial and a critical step in every wood processing production. During the hydrothermal treatment of wood, it is necessary to know with great certainty the specific type of wood specie that is being processed. There may be differences present within same wood genus that may affect hydrothermal wood processing especially kiln drying. It is not always the case that the lumber quality is questioned, but often because of uncertainty about how the lumber will behave, processing regimes that are being used are milder that they should be, and thereby, drying time is unnecessarily prolonged.

Consequently, hereinafter some examples of differences within same genus among similar wood species will be analysed and discussed. 3.1. Yellow heartwood discolouration of some wood species

From the practical experience it is known that during air and kiln drying of Pedunculate oak (Quercus robur L.) and Sessile oak (Quercus petraea (Matt.) Liebl.) yellowish discoloration of the heartwood may occur, and it mainly appears in the form of streaks in the direction of the wood fibres (Figure 3). Discoloured streaks are mostly extended from the cut ends to the interior of the lumber, however, this is not always the case.

Figure 3. Yellow stain streaks on the Quercus robur L. heartwood parquet flooring

(source: Gard et al., 2010)

BAUCH et al. (1991) establish that this kind of discolouration is caused by the mould-type fungus Paecilomyces variotii Bain. The reacting compounds are probably hydrolysable tannins, wherein reaction occurs between fungal metabolites and accessory compounds in the heartwood. The same authors determined that the longitudinally extended yellow discoloration occurs along and in the vicinity of the vessels, where within earlywood vessels thick hyphae grow into a netlike mycelium. It can also be localized in the ray and longitudinal parenchyma. However, this discolouration does not occur in the oak-wood sapwood despite the fact that the fungi develop in this part of the lumber as well. Paecilomyces variotii Bain. is a saprophytic fungi that is commonly occurring in air and food and thus lumber is very easily infected with its spores, because of its common presence in the air. Paecilomyces variotii Bain. is a thermotolerant and thermophilic type of fungus that was first described by Bainier


75

in 1907, and from species belonging to Paecilomyces section Paecilomyces it is the most commonly encountered (LUANGSA-ARD et at., 2004).

Figure 4. Paecilomyces variotii Bain. under light microscope, conidiophores (on the left), phialides

and conidia (on the right). (source: LUANGSA-ARD, et at. 2004)

SIMPSON (1991) states that Paecilomyces variotii Bain., forms lumber discoloration under

warm humid conditions particularly during predrying process if the air circulation is poor. Therefore, the final quality of the lumber depends on the ways in which raw material is treated at all stages that precede hydrothermal processing (KLARIĆ et al., 2012).

Figure 5. Yellow stain streaks on the Quercus robur L. heartwood parquet staves (photo: Klarić)

According to practical experience of the authors, Paecilomyces variotii Bain. caused

yellow stains vanish after some time of exposure to the sunlight in internal room conditions. Figure 5 shows the initial state of yellow stain on the parquet elements and the same strips after several months of exposure to sunlight in indoor conditions, after the stain is reduced is shown in Figure 6. One can notice a significant reduction of yellow stain visibility on Figure 5 compared to Figure 6.

Figure 6. Faded yellow stain on the Quercus robur L. heartwood after exposure to the sun light

(photo: Pervan and Klarić)

BAUCH et al. (1991) states that specific reacting heartwood compounds which are involved in yellow staining, were found in (Quercus robur L.), (Quercus Petrea [Mat.] Liebl.) and (Castanea sativa Mill.), while in (Quercus rubra L.) heartwood those compounds were not found. Consequently, it is very important to know accurately which exactly wood specie


76

is being processed, because in that way the occurrence of yellow staining can be excluded if we process the wood specie not prone to the yellow staining. Or vice versa, the emergence of staining can be expected if the wood specie which is prone to the occurrence of the yellow staining is being processed. Therefore, necessary precautions must be undertaken.

On the other hand, oak-wood heartwood is very susceptible to the cracks and colour change if it is exposed to high temperatures during initial stage of kiln drying process, while it still has high moisture content. Therefore, by maintenance of low dry-bulb temperature in order to avoid cracks and other types of discolouration, fungus may have the ideal prerequisite in the kiln for the growth, and hence yellow stain can occur during the initial stages of the kiln drying process. This type of fungus is thermotolerant and thermophilic which additionally stimulates its development. It can occur not only during the kiln drying, but also during the certain periods of the year while lumber is air-dried. Yellow stain may also be initiated if unprofiled stickers are used for lumber stacking. If that is the case, the moisture is retained below stickers and there is no air circulation and thus, fungus may easily develop.

Figure 7. Yellow stain on the Quercus robur L. heartwood flooring parquet

(source: http://www.myfloor.pl/z-praktyki-rzeczoznawcy-przebarwienia-debu-spowodowane-przez-grzyb-paecilomyces-variotti,509,artykul.html)

Frequently yellow stain occurs on the oak wood floorings, where it is aesthetically very

unacceptable, where furthermore, it can be even more pronounced after lacquering. 3.2. European Larch and Siberian Larch similarities and differences

Larch wood is significant construction and joinery wood source with high potential in Europe nowadays. Two larch species stand out among others in the same genus, namely, European larch (Larix decidua Mill.) and Siberian larch (Laix sibirica Ledeb.). Larch wood has preferred properties for outdoor application, it is partially decay resistant and has appealing growth ring patterns. According to GIERLINGER et al. (2004) and VENÄLÄINEN et al. (2006) in Larix species there is correlation between total phenols and decay resistance. Furthermore, according to POCKRANDT (2012), Siberian larch, when compared with European larch, has much higher decay resistance in-ground, and some higher decay resistance above ground. One should take into account that the mentioned experiment was carried out in Sweden, hence the decay resistance of those two species could differ in warmer parts of Europe.

Nowadays, larch wood is increasingly used for external doors and windows production. On the regional lumber market under the same trading name commonly are sold both, the European larch and the Siberian larch. Traders mostly do not distinguish those two species, and this can be misleading for the end users. In generally there are no crucial differences for the joinery production between European larch and Siberian larch. Siberian larch is slightly more decay resistant and has slightly higher mechanical properties due to its higher density of


77

wood, what is due to narrower growth rings and higher share of the latewood zone within the growth ring.

Table 2. Mean annual ring width, mean wood density and latewood proportion of some Larix sibirica

and Larix decidua according to KARLMAN et al. (2005)

Species Origin Mean annual ring width (year 1-20)

[mm]

Mean annual ring width

[mm]

Mean density (min – max)

[kg/m3]

Latewood proportion

[%]

L. sibirica Krasnoyarsk

(RUS) 2.38 1.08

639 (565-670)

39

L. decidua Lyrestad (SWE)

2.88 1.92 621

(550-665) 42

L. decidua Remningstorp 3.62 3.29 536

(515-560) 34

On the other hand, there is a significant variability in the density of the wood of Siberian

Larch, especially between earlywood and latewood, and also between origins (KOIZUMI et al., 2003).

Figure 8. Siberian larch cross-section (on the left)(photo: Pervan and Klarić),

European larch (on the right) (source: GODET, 2006)

The problem occurs when the larch wood has to be kiln dried. Siberian larch is more prone to drying defect occurrence than European larch. Distortion, cracks and especially micro cracks often occur. Denser wood is more prone to cracks occurrence during drying. The frequent problem is uneven final moisture content, which can cause problems during gluing and finishing process. Siberian larch is growing on a large area of the earth northern hemisphere, and therefore huge differences in properties between trees from different areas may be present. Siberian larch from the Finland and one from Siberia probably will not behave in the same way during the hydrothermal processes.

3.3. Tropical woods

In the commercial wood trade on the international market with tropical woods frequently many different wood species are frequently sold under the same common name. Excellent example of such case is frequently used common name “African Ebony”. The term African Ebony represents Diospyros spp. which originates from Africa, and according to KUKACHKA (1969) this is group of about forty species but only a few produce enough of the dark-coloured heartwood to be of economic importance. CHUDNOFF (1984) states that other common names for African Ebony are: Mgiriti, Msindi (Tanzania), Omenowa (Ghana), Kanran, Nyareti (Nigeria), and Kukuo (Gambia). Not only is there African Diospyros spp.,


78

there are also Diospyros spp. from equatorial belt all around the world, and if the term Ebony is used it can represent any of several dozens of wood species.

Figure 9. African Ebony (Diospyros mespiliformis) on the left, Mauritius Ebony (Diospyros melanida)

(source: xylarium of the Department for Wood Scence, Faculty of Forestry, University of Zagreb)

African Ebony heartwood is mostly uniformly dark coloured while Asian Ebony has lighter colour and is commonly striped. There are some African Ebony species, which can also be striped, but they are in generally darker coloured than striped Asian Ebony heartwood. The sapwood of both, African and Asian ebony is significantly lighter coloured and the difference between heartwood and sapwood is notable. American Diospyros spp. visually differ significantly from African and Asian Diospyros spp. The Diospyros spp. can be also completely light coloured, e.g. American Persimmon (Diospyros virginiana L.).

According to the Ministry of Natural Resources and Tourism of The United Republic of Tanzania, some Tanzanian growing Diospyros spp. together with vernacular names and the dialect used (in brackets) are listed in Table 3. It can be seen that there are many variations of vernacular names for the same wood specie within one African Republic. In addition, some vernacular names embraces several wood species, or the same dialect uses multiple names for the same species. Likewise, different dialects use the same vernacular name for different species.

Table 3. Some Diospyros species from Tanzania with local names and dialect used.

Scientific name

Vernacular name

Diospyros abyssinica

Mkeakiindi (Shambaa)

Mtitu (Shambaa)

Mnginyei (Maasai)

Diospyros fischeri

Mbonto (Shambaa)

Mdaa (Makonde)

Mdaha (Kwere)

Mfubata (Nyamwezi)

Mpatilavehe (Hehe)

Mumbiluilu (Nyaturu)

Diospyros mespiliformis

Mfisha (Fipa)

Mhena (Shambaa)

Mkulwe (Bondei)

Msinde (Nyamwezi)

Mkea kiindi (Shambaa)

Mtitu (Shambaa)

Diospyros whyteana

Mdengemsitu (Bena)

Msisina (Hehe)

Msisina (Shambaa)

Mtitu (Bena)

Mupatilavehe (Hehe)

Similar, encompassing common names are not only the case for the Ebony, but for the

vast number of tropical wood species. Furthermore, most of the tropical woods are difficult to dry, and are prone to defects, besides from each habitat the drying properties can be significantly different. Most of the European wood processing companies have no experience with kiln drying of tropical woods, and additionally, if the exact specie is not identified, drying defects are unavoidable. The one should be cautious when dealing with Ebony wood. It is very likely that wood processing company or end user when buying Ebony wood will not get the texture and colour of Ebony wood they initially desired. A great range of textures and colours of ebony wood are available on the international market, and the buyer should know


79

exactly what his preferences are, what specie or group of species fulfils the criteria, which are desirable for a specific purpose.

4. DISCUSSION

There are numerous examples of differences in between similar species originating from the same genus. On the final product those differences are mostly aesthetic, but during the production they may cause serious problems, such as defect occurrence, higher energy consumption etc. As regards to the end user, it is important for them to be well informed about scientific names of wood species before purchasing wooden products or semi products. If they are not well informed, it may happen that they will get the specie they did not pay for. During the lumber kiln drying if the exact specie is not known many drying defects can occur. If the wood specie which is kiln dried is more sensitive to the high initial temperature or moisture, and the kiln operator does not know that, casehardening, collapse, distortion, discoloration or cracks may occur. Another example is when the wood specie is not sensitive to the rapid kiln drying regime, and the operator does not know that, the kiln drying process will last longer than it should. That means that more electricity and more heat energy will be consumed, but not only the energy, also the kiln capacity and working time of involved workers will be lost. If the lumber that will be kiln dried is from and for the third persons than it is especially important to determine exact wood specie in order to avoid drying defects, and thus avoid inconveniences and unnecessary costs. There is a problem concerning vernacular wood species names, because their usage is confined mostly in a few languages, and they significantly vary not only from language to language, but also from region to region. Often family or generic relationships are not indicated via common names. Oak is similarly common name for the species of genus Quercus, but Tanbark oak is Lithocarpus, Poison oak a Rhus, Silver oak a Grevillea and Jerusalem oak a Chenopodium (SINGH, 2010). Common name can also be confusing when a specie has more than one common name what is especially the case if it is widely distributed in different localities. However, opposite problem appears when a certain species are so unfamiliar that they do not have common name.

In the Republic of Croatia there is a nice example of vernacular names for the Alnus glutinosa [L.] Gaertn., and its historical development, whereby the term “joha” is nowadays language standard, while term “jalša” is used in northern and western parts of Croatia as a dialectal and archaic expression. But that was not the case in the past. BALOG (2005) states that until the 17th century the variant “jalša” prevailed as the standard, and that all of the earlier confirmed toponyms are being derived from this variant. As a consequence of huge migrational changes, having to do with the Turkish conquests, “jalša” was evicted to the utter North and West of Croatia, while the regions in between use “joha”. 5. CONCLUSION

The use of scientific wood species names has many advantages, among which is international intelligibility. Whenever it is possible, one should use scientific wood species names to avoid misunderstandings during the international lumber trade. Likewise, especially during the hydrothermal wood processing and of course, during all stages of wood manipulation that precede hydrothermal wood processing. In doing so, wood defects avoidance will be ensured, implementation of prophylactic treatments will be facilitated, and last but not least, production cost will be reduced.


80

6. REFERENCES BALOG, Z. (2005): Jalša ili Joha – Toponomastičke teme. Cris: Journal of the Historical Society of

Križevci 7 (1): pp. 45-52. BAUCH, J.; v.HUNDT, H.; WEIßMANN, G.; LANGE, W.; KUBEL, H. (1991): On the Cause of the Yellow

Discolorations of Oak Heartwood (Quercus Sect. Robur) during Drying. Holzf. 45 (2): pp. 79-85. Bortnowski, C. (21. May 2013): My floor.

URL: http://www.myfloor.pl/z-praktyki-rzeczoznawcy-przebarwienia-debu-spowodowane-przez-grzyb-paecilomyces-variotti,509,artykul.html

CHUDNOFF, M. (1984): Tropical Timbers of the World. Agriculture Handbook Number 607. United States Department of Agriculture, Forest service, United States of America.

GARD, W. F.; GORIŠEK, Ž.; HRČKA, R.; KARASTERGIOU, S.; PERVAN, S.; SKARVELIS, M.; STRAŽE, A.; TRAVAN , L. (2010): Discolouration of timber in connection with drying. In: Welling, J.: Dried Timber – how to specify correctly. European Drying Group (EDG) and COST E 53.

GIERLINGER, N.; JACQUES, D.; SCHWANNINGER, M.; WIMMER, R.; PÂQUES, L. E. (2004): Heartwood extractives and lignin content of different larch species (Larix sp.) and relationships to brown-rot decay-resistance. Trees 18 (2): pp. 230-236.

GODET, J. D. (2006): Holzführer – Einheimische Holzarten mit Makroaufnahmen. Eugen Ulmer KG, Stuttgart, Germany. ISBN 978-3-8001-5197-4.

HOUGH, R. B. (2007): The Woodbook. Taschen, Köln, Germany. KARLMAN , L.; MÖRLING, T.; MARTINSSON, O. (2005): Wood Density, Annual Ring Width and

Latewood content in Larch and Scots Pine. Eurasian Journal of Forest Research 8 (2): pp. 91-96. KLARIĆ, M.; PERVAN, S.; PREKRAT, S.; BREZOVIĆ, M.; BIOŠIĆ, D. (2012): Oxidative Discolouration

of Alder Wood (Alnus spp.) During Hydrothermal Processing. In: Proceedings of Ambienta 2012 “Wood is Good – With Knowledge and Technology to Competitive Forestry and Wood Technology Sector”, Croatia, Zagreb, pp. 69-80. ISBN: 978-953-292-026-0.

KOIZUMI , A.; TAKATA , K.; YAMASHITA , K.; NAKADA , R. (2003): Anatomical characteristics and mechanical properties of Larix sibirica grown in South-Central Siberia. IAWA Journal 24 (4): pp. 355-370.

KUKACHKA , B. F. (1969): Properties of Imported Tropical Woods. United States Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, Wisconsin.

LUANGSA-ARD, J. J.; MANOCH, L.; HYWEL-JONES, N.; ARTJARIYASRIPONG, S.; SAMSON, R. A. (2004): Thermotolerant and Thermoresistant Paecilomyces and its Teleomorphic States Isolated from Thai Forest and Mountain Soils. Kasetsart Journal 38 (1): pp. 94-101.

MCNEILL, J.; BARRIE, F. R.; BUCK, W. R.; DEMOULIN, V.; GREUTER, W.; HAWKSWORTH, D. L.; HERENDEEN, P. S; KNAPP, S.; MARHOLD, K.; PRADO, J.; PRUD’HOMME VAN REINE, W. F.; SMITH , G. F.; WIERSEMA, J. H.; TURLAND, N. J. (2012): International Code of Nomenclature for Algae, Fungi, and Plants (MELBOURNE CODE), adopted by the Eighteenth International Botanical Congress Melbourne, Australia, July 2011. Koeltz Scientific Books, Germany, ISBN 978-3-87429-425-6.

POCKRANDT, M. (2012): Durability of Selected Larch Species and Scots Pine (Pinus sylvestris L.) Heartwood. In: Proceedings of the 8th meeting of WSE: pp. 129-135. Kaunas, Lithuania. ISBN 978-609-02-0581-5.

ROOS, J. A.; DONOVAN, G.; NICHOLLS, D.; (2005): How dose Species Name Affect Consumer Choice? An Analysis and Implications for Cabinet Door Marketers. Forest Prod. Journal 55 (5): pp. 21-26.

SIMPSON, W. T. (1991): Dry Kiln Operator’s Manual. Chapter 8. Drying defects pp. 179-206. United States Department of Agriculture, Forest Products Laboratory, Madison, Wisconsin.

SIMPSON, M. G. (2010): Plant Systematics, Second Edition, Elsevier, United States of America. ISBN 978-0-12-374380-0.

SINGH, G. (2010): Plant Systematics – An Integrated Approach, Third Edition, Science Publishers, United States of America. ISBN 978-1-57808-668-9.

STUESSY, T. F. (2009): Plant Taxonomy – The Systematic Evaluation of Comparative Data. Second edition, Columbia University Press, New York, USA. ISBN 978-0-231-14712-5.

TRAJKOVIĆ, J. (2013) Personal communication. VENÄLÄINEN , M.; HARJU, A. M.; TERZIEV, N.; LAAKSO, T.; SARANPÄÄ, P. (2006): Decay resistance, extractive content, and water sorption capacity

of Siberian Larch (Larix sibirica Ledeb.) heartwood timber. Holzforschung 60 (1): pp. 99-103.


81

Environmental Impact Assessment as part of Furniture Design

KUTNAR Andrejaa – KUŠAR Tomažb – KITEK KUZMAN Manjab* a Andrej Marušič Institute, University of Primorska, Koper, Slovenia

b Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia

*Corresponding author: [email protected] Abstract – With sustainability being the driving force in the world, environmental impact assessment should be included also in furniture design. In this study design of a bed for elderly people, while considering the carbon footprint of the selected material - solid beech wood was performed following the Cradle to Cradle concept. The designed bed was a multifunctional bed that enables the fullfilment of specific needs of the end - users - senior citizens. Based on the drawings of the bed, the necessary quantities of the selected material and the amounts of wood residues were determined. For the designed bed the carbon footprint was calculated following the standard PAS 2050. The results have shown that the NET carbon footprint of designed bed is negative, due to sequestrated carbon in the wooden elements of the product. Furthermore, the study showed that coatings and adhesives considerbly contribute to the carbon footprint, although they have low contribution to the weight of the whole product. Therefore, it was concluded that coatings and adhesives from renewable resources should be used to reduce the environmental impact of the designed bed for elderly people.

carbon footprint / furniture design / environmental assessment / cradle to cradle 1. INTRODUCTION

In the past the emergence of inexpensive materials and advanced technology led societies

into mass consumption, generation of enormous amounts of waste and consequently landfilling. At that time, environmental matters and sustainable development were of low concern. During the following decade, different environmental disasters reminded the academicians, politicians, the media, and society in general to think about such issues like oil catastrophes, green-house-effects and dying forests. Terms like recycling, reuse, resource reduction, environmental manufacturing responsibility and green products began to be familiar to all of us.

Today, a lot of wooden products that could be utilized in a secondary product life cycle are burned for the production of energy or are just down-cycled so that they are losing the favourable material properties of solid wood. On one hand, this reduces the competitiveness of wood as a construction or raw material not only from the ecological, but also from the business point of view. On the other hand, it offers an obvious opportunity for innovative companies to create new business models, processes, and products. One of them can be found in the area of wooden product cycling with continuous loops in production, following the Cradle to Cradle (C2C) concept, developed by William McDonough and Michael Braungart (VEZZOLI et al., 2010). The C2C concept is a shift from eco-efficiency towards eco-effectiveness with continuous loops in production. It is not about doing more with less and reducing waste (cradle to grave), but about “doing it right” from the beginning. Materials should circulate in continuous loops and the waste of one process becomes the “food” for another process.

With regard to greenhouse gas (GHG) emissions, wood is a better alternative than other materials (less SO2 emissions, less waste) (PETERSEN – SOLBERG, 2005). However, treated wood, wood bonded by synthetic adhesives and coated wood (synthetic coatings), on the other hand, might have toxicological impacts on human health and ecosystems. The fossil fuel consumption, potential contributions to the greenhouse effect and quantities of solid waste


82

tend to be minor for solid wood products, compared to the competing ones (WERNER –

RICHTER, 2007). In contrast, wood based composites, such as particle boards or fibreboards, which make use of a larger share of wood of a tree, compared to solid wood products, have a high consumption of fossil energy associated with the production of fibres and particles/chips, as well as with the production of glues, resins, etc. (WERNER – RICHTER, 2007). Therefore, the renewable energy should rather be used to produce wood-based products.

When developing Cradle to Cradle products also social responsibility has to be included in the design. To respect diversity in designing a product means to take into consideration not only how it is made but also who will use it and how, in different ways, places and moments. This principle can be followed in many ways. For example, products can enable that they are adapted and changed in relation to different phenomena: technology evolves but the environmental context in which the product is used, and the physical and cultural characteristics of the user, can evolve as well. Upgradability and adaptability should then be facilitated and it is necessary to design flexible, modular and reconfigurable products, in relation to dimensions, performance and appearance. For example, furniture for elderly people should be designed in a way that it is anthropometrically and ergonomically adjusted to them. The design should include both safety and functionality and incorporate the specific needs of the end-users - senior citizens, who often require aid at home and have different design needs than those who are capable of living by themselves.

Owing to an increasingly higher standard of living as well as improvements in health care, the proportion of senior citizens in the general population is rapidly increasing. Statistical prognosis indicates that, by 2030, 36 % of people will be over the age of 60 (HILDERBRAND, 2002). Information from the Statistical Office of the Republic of Slovenia states that, in 2010, the percentage of Slovenian citizens over 60 years of age was 22 %, out of which 58 % were female. There had also been an increase in the number of citizens with sight issues, hampered movement capabilities, and degrees of memory loss. According to data issued by the Statistical Office of the Republic of Slovenia, citizens over the age of 60 accounted for only 12 % of the changes made to residences in 2008. Other data suggests that senior citizens rarely decide to change their home environments, which contribute to a lowering of comfort levels and environments ill–suited for accommodating residents with special needs, and to lower safety levels. Most people are also reluctant to live in a retirement home, and only do so when they are entirely incapable of living by themselves. In Slovenia, 7 % of the population resides in a retirement home. However, in 2011 the number of elderly people that lived in a retirement homes and other social welfare institutions increase in comparison to the year 2010 by more than 4 %. For the year 2011 the statistics are reporting 22921 people living in retirement homes and social welfare institutions. Additionally, according to research Home REMODELLING (2006), 60 % of the senior population lives in homes that have not been renovated or refurnished for over 20 years, contributing to lower safety and comfort levels. Comfort is crucial for the elderly, as they spend most of their time at home. Over 14 % of English elder citizens live in unfit conditions, in homes that are in dire need of renovation and adaptation (BOYO, 2001). Yet only 10 % of them decide to modify their existing furniture and equipment to reflect their special needs (GILDERBLOOM et al., 1996). They often refrain from renovating due to financial concerns, lessening mobility and fear of the upheaval of renovation work. Furthermore, the research also shows that the elderly also suffer from inappropriate room dimensions including rooms that are too big for them (WEST – EMMITT , 2004).

Following the C2C this study aimed to design flexible, reconfigurable, healthy, and safe bed out of solid beech wood with “zero waste”, which involves substitution of toxic elements, material reutilization, renewable energy use, water stewardship, and social responsibility, and at the same time enables the assistance to elderly people with changing needs.


83

2. METHODOLOGY OF CARBON FOOTPRINT CALCULATION 2.1. Goal and scope of the Carbon Footprint Calculation

Following the common Life Cycle Assessment (LCA) methodology (ISO 14044, PAS 2050) the goal of the study was to objectively prove environmental impact from “cradle to gate”, an assessment of a partial product life cycle from manufacture ('cradle') to the factory gate (i.e., before it is transported to the consumer), of designed bed for elderly people. The main focus was given to the carbon footprint. The functional unit was chosen to be the whole bed.

The use phase and disposal phase of the product were omitted. Analysis included carbon emissions of raw materials and waste resulting from product production, while transportation of materials to the factory, electricity and other energy sources in product production were not included in the calculation.

2.2. Analysed product and data collection

The bed was designed keeping in mind the comfort and needs of old and ailing people. The conflict between designing for an individual and designing for a population was faced: a product that suits one person may be inconvenient to another. The ergonomic approach to home design may develop an integrated strategy aimed at the well being and satisfaction of ageing people (PINTO et al., 2000). Common habits of elderly people were analysed to design a bed that meet their changing needs. In bed, ageing people are liable to risks of falls and impacts. Furthermore, the mobility and physical ability of elderly people are changing over time. Therefore, the simple multifunctional bed that gives warm feeling of familiarity and orientation with the environment was designed. The design included the following requirements: the option to adjust height, maintaining person position, moving and turning part of bed, raising head and legs, bed rail, vertical grab pole, bed accessories should enable eating and other activities in bed, while all the appliances should be easy to use involving simple commands.

The designed bed (width 90 cm, length 200 cm, and height 45 cm) that included the above requirements is shown in Figure 1. The selected construction material was beech (Fagus sylvatica). The elements of the designed bed, their dimensions, and needed volume of wood for each element, accounting also the yield, are given in Table 1.

Figure 1. Bed for elderly people designed following the C2C concept


84

Table 1. List of solid wood elements, their dimensions, and amount of material needed for designed bed.

Elements Dimensions Number

of pieces

Volume (net)

Yield

Needed volume

accounting yield

Length [mm]

Width [mm]

Height [mm]

[m3]

[%]

[m3]

Leg - headboard 1200 40 40 2 0.0038 60 0.0064 Leg -footboard 750 40 40 2 0.0024 60 0.0040 Headboard 900 900 20 1 0.0162 60 0.0270 Trapeze bar 900 170 25 1 0.0038 60 0.0064 Food board 900 570 20 1 0.0103 60 0.0171 Board 2030 200 20 2 0.0162 60 0.0271 Side rail 1950 30 30 2 0.0035 60 0.0059 Rail 2030 70 20 2 0.0057 60 0.0095

Following the elements given in Table 1, the list of materials needed for production of

designed bed was determined. The amounts of materials were assessed and used for carbon footprint and net carbon foot print calculation (Table 2). Table 2. List of input materials for calculation of carbon footprint and their quantities for the designed bed for elderly people

Input materials Solid wood 0.103 m3 Metal conecting elements 128 g Metal swivel clamp 70 g Adhesive PVA 200 g Water based coating 1 450 g

Based on the determined goal and scope of the study, the life cycle inventory of

input/output data for the carbon footprint calculations was performed. Data of energy inputs, raw materials, products, co-products, waste, and releases to air, water and soil were assessed. The upstream life cycle impacts of input materials were not analysed specifically for this project. Instead, sound secondary life cycle data (emission factors) were sourced from Ecoinvent database 2.0. (2010). 2.3. Modelling and impact assessment

The data collected were modelled in Simapro (SimaPro Analyst Indefinite, Ecoinvent v2, Product Ecology Consultants, PEC, Netherlands). Emissions and consumptions were translated into environmental effects, which were grouped and weighed. The biotic carbon sequestration was considered in the calculation. Carbon footprint was calculated with methodology IPCC 2001 GWP 100a V1.02 (CLIMATE CHANGE, 2001). IPCC 2007 contains the climate change factors of IPCC with a timeframe of 100 years. IPCC characterization factors for the direct (except CH4) global warming potential of air emissions. They do not include indirect formation of dinitrogen monoxide from nitrogen emissions, do not account for radiation forcing due to emissions of NOx, water, sulphate, etc. in the lower stratosphere + upper troposphere, do not consider the range of indirect effects given by IPCC, and do not include indirect effects of CO emissions.


85

3. RESULTS

Carbon footprint calculates the amount of green house gas (GHG) emissions caused by a particular activity or entity, commonly also referred to as global warming potential (GWP). It is measured in tones (or kilograms) of carbon dioxide equivalent (CO2eq.). Approximately 50 % of dry timber is elemental carbon; thus, 1 kg of wood contains approximately 0.5 kg of carbon, which equates to 1.83 kg of CO2. When calculating a carbon footprint, whether to include this stored carbon in timber (and, to a far lesser extent, small amounts of stored carbon in other materials) is a much debated issue. In this study, the carbon footprint and NET carbon footprint were calculated. The carbon footprint of the designed bed analysed product was 10.4 kg CO2e, while the NET carbon footprint was – 107.4 kg CO2e due to carbon storage (sequestration) in the product, which was 117.8 kg CO2e (Table 3). Table 3. Carbon footprint, CO2eq sequestered in the product, and NET carbon footprint of designed bed for elderly people

Carbon footprint

[kg CO2e]

CO2eq. sequestered in the product [kg CO2e]

NET carbon footprint* [kg CO2e]

Bed for elderly 10.4 117.8 - 107.4 * includes carbon storage (sequestration)

In Table 4 and Figure 2, the contributions of input materials to carbon footprint are given. Although the water-based coating presented low contribution to the weight of the whole product (2.2 %), it contributed a significant 29.5 % to the carbon footprint. On the other hand, the timber presented high contribution to the weight of the product (97.2 %), but it contributed only 63.9 % to the carbon footprint of the designed bed for elderly people. Furthermore, metal parts and adhesive contributed 3 % to the carbon footprint of the designed bed for elderly people. Table 4. Carbon footprint of emission sources and their contribution to the total carbon footprint of designed bed for elderly people

Input materials kg CO2e Sawn timber, hardwood, raw, air / kiln dried, u=10 % 6.65 Polyvinyl chloride resin 0.359 Steel, converter, unalloyed, 0.317 Acrylic dispersion, 65 % in H2O 3.07 Total 10.4

Figure 2. Contribution of emission sources to carbon footprint of the “bed for elderly people”.

64%

3%

3%

30%

Sawn timber, hardwood, raw, air / kiln dried, u=10%Polyvinyl chloride resin

Steel, converter, unalloyed,

Acrylic dispersion, 65% in H2O


86

4. CONCLUSIONS The study showed that coatings and adhesives considerably contribute to the carbon

footprint, although they have low contribution to the weight of the whole product. Therefore, coatings and adhesives from renewable resources should be used to reduce the environmental impact of the designed bed for elderly people. Furthermore, the study demonstrated that the LCA is a rational, quantified approach to determining specific environmental impacts of a product. As solutions are sought to reduce the impacts of products, LCA is seen as an objective measure for comparing products designs. LCA clearly has an important role to play in assessing the sustainability of green products and it is a valuable tool. The adoption of life-cycle approach to design, where not only current energy concerns are accounted for, but also long-term energy, environmental, and social impacts, should lead to an integrated approach to design. Future research will investigate the bed for elderly people made out of a solid beech wood in combination with veneered particleboard, and out of a solid beech wood in combination with beech plywood with the aim to determine the best solution, when the environmental impact is the measure of a material selection process, including the energy use of the production process. Furthermore, the prototype of multifunctional bed will be produced and simulation results will demonstrate the effectiveness of the proposed design. Acknowledgements: We wish to thank the Slovenian Research Agency within the frame of program P4-0015. 5. REFERENCES BOYO, S. (2001): When a house is not a home. Older People and their housing, London: AGE – Age

Concern England: 65. ECOINVENT 2.0 (2010): Swiss Centre for Life Cycle Inventories, Dübendorf, Switzerland. GILDERBLOOM, J.I.; AFFAIRS, U.; MARKHAM , J.P. (1996): Housing Modifi cation Needs of the

Disabled Elderly: What Really Matters?. Environment and Behavior 28(4): pp. 512-535. HILDERBRAND, H. 2002: Fur Altere und Behinderte. BM 57 (3): pp. 36 HOME REMODELING (2005): Why Is Home Modification And Repair Important?

URL: http://www.aoa.gov/ eldfam/Housing/Home_Remodeling/Home_Remodeling.asp ISO STANDARD 14040 (2006): Environmental management - Life cycle assessment - Principles and

framework. ISO STANDARD 14044 (2006): Environmental management - Life cycle assessment - Requirements and

guidelines. MEZZOLI, C.; ORBETEGLI, L.; CORTESI, S. (2010): C2C Network, Prospective Study: Industry.

URL: http:// www.c2cn.eu PAS 2050 (2011): Specification for the assessment of the life cycle greenhouse gas emissions of goods

and services. BSI, UK. PETERSEN, A.K.; SOLBERG, B. (2005): Environmental and economic impacts of substitution between

wood products and alternative materials: a review of micro-level anayses from Norway and Sweden. Forest Policy and Economics 7: pp. 249-259.

PINTO, M.R.; DE MEDICI, S. (2000): Ergonomics, gerontechnology, and design for the home environment. Applied Ergonomics 31 (3): pp. 317-322.

SIMPRO (2009): SimaPro Analyst Indefinite, Ecoinvent v2, Product Ecology Consultants, PEC, Nizozemska. URL: http:// www.pre.nl/default.htm

STATISTIC OFFICE (2010): POPIS 2002. URL: http://www.stat.si/popis2002/si/rezultati/rezultati_red.asp?ter=SLO&st=44

WERNER, F.; RICHTER, K. (2007): Wood building products in comparative LCA. A literature review. Int J LCA, 12 (7): pp.470-479.

WEST, B.N.; EMMITT , S. 2004: Functional design? An analysis of new speculative house plans in the UK. Design Studies 25: pp. 275-299.


87

Comparative Analysis of Stiffness Coefficients of End and T-shape Corner Joints of Frame Structural Elements with Two Types of Cross Sections

made of Sweet Chestnut Wood

KYUCHUKOV Georgia – GRUEVSKI Georgib – MARINOVA Assiaa – KYUCHUKOV Borislava JIVKOV Vassila*

a University of Forestry, Sofia, Bulgaria b Ss. Cyril and Methodius University, Skopje, R. of Macedonia


Abstract – The present study involves a comparative analysis of experimentally established stiffness coefficients under compression bending test of some of the most frequently used end and T-shape corner joints of frame structural elements with two types of rectangular cross sections – with size of 50x25 mm and 50x30 mm, made of sweet chestnut solid wood. It was established that the type of the joints has a determining influence on their stiffness characteristics. The T-shape corner joints have on average 7.6 % and 11.2 % greater stiffness coefficient then the one of the end corner joints respectively for thickness of the elements 25 and 30 mm. With an increase of the thickness of the cross section from 25 mm to 30 mm, the stiffness coefficient of the end and T-shape corner joints increases on average by about 27 % and 32 %, respectively. It is recommended that the stiffness coefficients of the tested corner joints have to be taken into account when choosing the type of joints in the chair constructions.

end and T-shape corner joints / structural elements / stiffness coefficients / compression bending test / chair constructions / sweet chestnut solid wood 1. INTRODUCTION

The stiffness characteristic of the corner joints is one of the main factors determining the shape stability of the sitting furniture constructions, as well as their stability and durability at service use. The stiffness characteristic depends on a number of factors – the tree species and physical and mechanical properties of wood, the cross section of the joined structural elements, the type and parameters of the joints, the properties of the glue line of the joints, the joints’ tightness, the roughness of the contacting surfaces of the joined structural elements, etc. Given this, in the research laboratories for furniture structural design, tests are consistently carried out on the ultimate bending moments and stiffness coefficients of the corner joints of the sitting furniture constructions, simulating service load (ALBIN et al., 1986; ERDIL et al., 2005; GRUEVSKI, 2007; JIVKOV , 2001; KYUCHUKOV et al., 2008a; KYUCHUKOV et al., 2008b; KYUCHUKOV et al., 2009; KYUCHUKOV et al., 2010; KYUCHUKOV et al., 2011a; KYUCHUKOV et al., 2012a; KYUCHUKOV et al., 2012b; TANKUT et al., 2005, ZHANG et al., 2001). It is relatively rare to find scientific studies about stiffness characteristics of these types of corner joints. To this end, the present study is designed to do a comparative analysis of experimentally established stiffness coefficients under compression bending test of some of the most frequently used end and T-shape corner joints of frame structural elements with two types of rectangular cross sections – with size of 50x25 mm and 50x30 mm, made of sweet chestnut solid wood. 2. MATERIAL AND METHODS

The type of the tested corner joints of the frame structural elements are sketched in


88

Figure 1 and Figure 2. The type, shape and dimensions of the samples (Figure 3), as well as their preparation, conditioning and testing under compression bending load were described in the previous publications (GRUEVSKI, 2007; JIVKOV , 2001; KYUCHUKOV et al., 2008a; KYUCHUKOV et al., 2008b; KYUCHUKOV et al., 2009; KYUCHUKOV et al., 2010; KYUCHUKOV et al., 2011a).

Figure 1. End corner joints of structural elements made of sweet chestnut solid wood:

Glued corner joints: 1 – open mortise and tenon joint; 2 – half-open mortise and tenon joint; 3 – haunched mortise and tenon joint; 4 – mortise and tenon joint; 5 – joint with two dowels ϕ 10 mm;

6 – joint with wooden “Lamello plates” Disconnected corner joints: 7 – joint with two countersunk screws for wood; 8 – joint with two one-

piece connectors “Confirmat”; 9 – joint with two connectors with screw and cross dowel

Figure 2. T-shape corner joints of structural elements made of sweet chestnut solid wood:

Glued corner joints: 1 – stub mortise and tenon, type A; 2 – through mortise and tenon type A; 3 – stub mortise and tenon with shoulders, type B; 4 – through mortise and tenon with shoulders,

type B; 5 – joint with two dowels ϕ 10 mm; 6 – joint with wooden “Lamello plates” Disconnected corner joints: 7 – joint with two countersunk screws for wood; 8 – joint with two one-

piece connectors “Confirmat”; 9 – joint with two connectors with screw and cross dowel


89

Figure 3. Dimensions and testing schemes of the samples under compression bending load: a and b – end corner joints; c and d – T-shape corner joints

3. COMPARATIVE ANALYSIS OF THE RESULTS

Comparative data of the results from the experimental studies on the stiffness coefficients of the tested corner joints is presented in Table 1. Figure 4 and Figure 5 give a graphical idea of the ratio of the stiffness coefficients of the tested types of corner joints.

The data indicates that the type of joints has a determining influence on their stiffness coefficients under bending load.

Figure 4. Comparative data of the stiffness coefficients of the tested end corner joints of structural

elements with cross section of 50 x 25 mm and 50 x 30 mm made of sweet chestnut solid wood according to Table 1

According to the stiffness coefficients’ values, the glued end corner joints (Figure 1) with rectangular cross section of 50x25 mm are set in the following hierarchical order: open mortise and tenon joint, half-open mortise and tenon joint, haunched mortise and tenon joint, mortise and tenon joint, joint with two dowels φ 10 mm and joint with wooden “Lamello plates”. Among the tested dismountable end corner joints with cross section of 50x25 mm, the joint with two one-piece connectors “Confirmat” has the highest stiffness coefficient, followed by the joint with two counter-sunk screws for wood and the joint with two connectors with screw and cross dowel.


90

Table 1. Stiffness coefficients under compression bending loading of the corner joints of structural elements with rectangular cross section 50x 25 mm and 50 x 30 mm made of sweet chestnut solid wood

Type of the corner joints

Stiffness coefficients for cross sections of the structural elements:

50 x 25 mm, c1, N.m/rad

50 x 30 mm, c2, N.m/rad

Ratio c2/c1

A. End corner joints I. Glued corner joints 1. Open mortise and tenon joint 8 060 9 850 1,22 2. Half-open mortise and tenon joint 7 800 9 600 1,23 3. Haunched mortise and tenon joint 7 700 9 470 1,23 4. Mortise and tenon joint 7 500 9 240 1,23 5. Joint with two dowels φ 10 mm 7 060 8 930 1,26 6. Joint with wooden “Lamello plates” 6 000 8 040 1,34 II. Dismountable corner joints 7. Joint with two counter-sunk screws for wood 3 500 4 480 1,28 8. Joint with two one-piece connectors “Confirmat” 4 200 5 540 1,32 9. Joint with two connectors with screw and cross dowel 3 400 4 420 1,30 B. T-shape corner joints I. Glued corner joints 1. Stub mortise and tenon joint, type A 8 080 10 260 1,27 2. Through mortise and tenon joint, type A 8 610 11 760 1,37 3. Stub mortise and tenon with shoulders, type B 7 500 9 820 1,31 4. Through mortise and tenon with shoulders, type B 7 580 10 360 1,37 5. Joint with two dowels φ 10 mm 7 080 8 980 1,27 6. Joint with wooden “Lamello plates” 6 020 8 920 1,48 II. Dismountable corner joints 7. Joint with two counter-sunk screws for wood 3 810 5 040 1,32 8. Joint with two one-piece connectors “Confirmat” 4 850 5 620 1,16 9. Joint with two connectors with screw and cross dowel 4 370 5 870 1,34

According to the stiffness coefficients’ values, the glued T-shape corner joints (Figure 2)

with rectangular cross section of 50x25 mm are set in the following hierarchical order: through mortise and tenon joint, type A; stub mortise and tenon joint, type A; through mortise and tenon joint with shoulders, type B; stub mortise and tenon joint, type B; joint with two dowels φ 10 mm; joint with wooden “Lamello plates”. Among the tested dismountable T-shape corner joints with cross section of 50x25 mm, the joint with two one-piece connectors “Confirmat” has the highest stiffness coefficient, followed by the joint with two connectors with screw and cross dowel and the joint with two counter-sunk screws for wood.

According to the stiffness coefficients’ values, the glued and dismountable end corner joints (see Figure 1) with rectangular cross section of 50x30 mm are set in the same hierarchical order as the joints of structural elements with size of cross section 50x25 mm.

Among all tested glued T-shape corner joints (Figure 2) with cross section of 50x30 mm, the through mortise and tenon joint, type A, has the highest stiffness coefficient. Following in a decreasing order are the through mortise and tenon joint with shoulders, type B, the stub mortise and tenon joint, type A, the stub mortise and tenon joint, type B, the joint with two dowels f 10 mm, and the joint with wooden “Lamello plates”. Among the tested dismountable corner joints with cross section of 50x30 mm, highest is the stiffness coefficient of the joint with two connectors with screw and cross dowel, followed by the joint with two one-piece connectors “Confirmat” and the joint with two counter-sunk screws for wood.


91

Figure 5. Comparative data of the stiffness coefficients of the tested T-shape corner joints of structural

elements with cross section of 50 x 25 mm and 50 x 30 mm made of sweet chestnut solid wood according to Table 1

The difference in the hierarchical order of the stiffness coefficients of all tested end and

T-shape corner joints of structural elements with rectangular cross section of 50x30 mm in comparison with those with rectangular cross section of 50x25 mm is a result of the different mode of failure in the joints. The bigger thickness of the structural elements results in proportionately fewer wood failures of the structural elements compared to failures of their joining elements.

The data in Table 1 also indicates that the cross section of the structural elements influences significantly the stiffness characteristic under bending load of the corner joints. The ratio between the stiffness coefficients of the glued end corner joints of structural elements with cross section of 50x30 mm and 50x25 mm, respectively, is on average 1.25, i.e. increasing of the cross section’s thickness from 25 mm to 30 mm increases the stiffness coefficient by about 25 %. The ratio between the stiffness coefficients of the dismountable end corner joints of structural elements with cross section of 50x30 mm and 50x25 mm, is on average 1.30, i.e. increasing of the cross section’s thickness from 25 mm to 30 mm increases the stiffness coefficient by about 30 %. The average increase of the stiffness coefficients of the glued and dismountable end corner joints is about 27 %.

The ratio between the stiffness coefficients of the glued T-shape corner joints of structural elements with cross section of 50x30 mm and 50x25 mm, respectively, is on average 1.34, i.e. increasing of the cross section’s thickness from 25 mm to 30 mm increases the stiffness coefficient by about 34 %. The ratio between the stiffness coefficients of the dismountable T-shape corner joints of structural elements with cross section of 50x30 mm and 50x25 mm, is on average 1.27, i.e. increasing of the cross section’s thickness from 25 mm to 30 mm increases the stiffness coefficient by about 27 %. The average increase of the stiffness coefficients of the glued and dismountable T-shape corner joints is about 32 %.

4. CONCLUSION

The results of the comparative analysis of the stiffness coefficients under compression bending test of the most frequently used end and T-shape corner joints of frame structural elements with two types of rectangular cross sections – with size of 50x25 mm and 50x30 mm - made of sweet chestnut solid wood gave reason to the following general conclusions and recommendations:

80808610

7500 75807080

6020

38104850

4370

10260

11760

9820 10360

8980 8920

50405620 5870

0

2000

4000

6000

8000

10000

12000

14000

1 2 3 4 5 6 7 8 9

С1,

С2,

Nm

/rad

Type of corner joints

Cross section 50х25 mmCross section 50х30 mm


92

1. The type of the joints has a determining influence on their stiffness characteristics under bending load.

2. The size of the cross section of the structural elements influences considerably the stiffness coefficient of the joints. An increase of the cross section’s thickness from 25 mm to 30 mm increases the stiffness coefficient of the end glued and dismountable corner joints by about 25 % and 30 %, respectively, (or about 27 % on an average). For the T-shape corner joints the corresponding increases are 34 % and 27 %, respectively, (or about 32 % on an average).

3. It is recommended that the size of the cross section of the structural elements of the corner joints made of solid wood and their stiffness coefficients under bending load be taken into account when choosing the type of the joints in the construction of the designed models of sitting furniture, as well as at strength and stiffness dimensioning of this kind of furniture.

5. REFERENCES ALBIN , R.; SCHMELMER, B. (1986): Beigefestigkeit von gedübelten Verbindungen bei Gestellmöbeln.

Holz als Roh- und Werkstoff 44 (2): p.76. ERDIL, Y.; KASAL, A.; ECKELMAN , C. (2005): Bending Moment Capacity of Rectangular Mortise and

Tenon Furniture Joints. Forest Products Journal 55 (12): pp.209-213. GRUEVSKI G. (2007): Izstrajuvanja na sostavite vo konstruktsiite na stolovi izraboteni od kostenovo

drwo, Doktorska disertacia, Faculty of Forestry, Skopje. JIVKOV , V. (2001): Influence of the tolerances on the strength characteristics of the main glued joints

of furniture. Ph.D thesis, University of Forestry, Sofia. KYUCHUKOV, G.; GRUEVSKI, G.; MARINOVA, А.; KYUCHUKOV, B. (2008a): Stiffness Coefficients

under Bending Test of End Corner Joints of Frame Structural Elements made of Sweet Chestnut Wood. In: Proceedings of the 7th International Symposium “Furniture 2008”, Faculty of Wood Science and Technology, Zvolen, Slovakia, ISBN 978-80-228-1839-1.

KYUCHUKOV, G.; GRUEVSKI, G.; MARINOVA, А.; KYUCHUKOV, B. (2008b): Stiffness Coefficients under Bending Test of T-shape Corner Joints of Frame Structural Elements made of Sweet Chestnut Wood. In: Proceedings “Innovation in Woodworking Industry and Engineering Design”, University of Forestry, Sofia, November 2008: pp. 265-270.

KYUCHUKOV, G.; GRUEVSKI, G.; MARINOVA, А.; KYUCHUKOV, B. (2009): Comparative Analysis of Stiffness Coefficients of End and T-shape Corner Joints of Frame Structural Elements made of Sweet Chestnut Wood. In: Proceedings of the 20th International Scientific Conference, University of Zagreb, October 2009: pp. 101-104.

KYUCHUKOV, G.; GRUEVSKI, G.; KYUCHUKOV, B. (2010): Comparative Studies on Destructive Bending Moments of End Corner Joints of Components of Solid Chestnut Wood with a Cross Section of 50 x 25 mm. In: Proceedings “Innovation in Woodworking Industry and Engineering Design”, Sofia, November 2010: pp. 206-210.

KYUCHUKOV, G.; GRUEVSKI, G.; MARINOVA, А.; KYUCHUKOV, B.; JIVKOV , V. (2011a): Stiffness Coefficients under Bending Test of End Corner Joints of Structural Elements made of Sweet Chestnut Wood. In: Proceedings of the 22th International Scientific Conference, University of Zagreb, October 2011: pp. 89-97.

KYUCHUKOV, G.; KYUCHUKOV, B.; JIVKOV , V.; MARINOVA, А. (2011b): Physical and Mechanical and Technological Properties of Wood of Some Valuable Tree Species in Bulgaria. Monograph, Avangard Prima, Sofia, 232 p.

KYUCHUKOV, G.; GRUEVSKI, G.; MARINOVA, А.; KYUCHUKOV, B.; JIVKOV , V. (2012a): Stiffness Coefficients under Bending Test of T-shape Corner Joints of Frame Structural Elements with Cross Section of 50 x 30 mm made of Sweet Chestnut Wood. In: Proceedings of the 23-rd International Scientific Conference, University of Zagreb, October 2012: pp. 97-102.

KYUCHUKOV, G.; GRUEVSKI, G.; KYUCHUKOV, B. (2012b): Comparative Studies on Destructive Bending Moments of T-shape Corner Joints of Frame Structural Elements made of Sweet


93

Chestnut Wood with a Cross Section of 50 x 25 mm. In: Proceedings “Innovation in Woodworking Industry and Engineering Design”, Sofia, 1/2012: pp. 79-85.

TANKUT, A.; TANKUT, N. (2005): The Effects of Joints Forms and Dimensions on the Strengths of Mortise and Tenon Joints. Turkish Journal of Agricultural and Forest 29: pp. 493-498.

ZHANG, J.; QUIN, F.; TACKETT, B. (2001): Bending Strength and Stiffness of Two-Pin Dowel Joints Constructed of Wood and Wood Composites. Forest Products Journal 51 (2): pp. 29-35.

DER GROßE HÄFELE, (2012): Möbelbeschläge. Katalog, Nagold.


95

Durability of Waterborne Coating Systems for Wooden Windows

MIKLEČIĆ Josipa*– JIROUŠ-RAJKOVIĆ Vlatkaa – ŠPOLJAR Marina a Department for Furniture and Wood Products, Faculty of Forestry, University of Zagreb, Zagreb, Croatia


Abstract – Artificial weathering method in accordance with HRN EN 927-6 was used for the evaluation of the behaviour of coating systems for wooden windows. Three opaque waterborne coating systems and three semi-transparent coating systems were used in this research. The test was carried out on test specimens made of spruce wood. Surface properties of used coating systems were compared with ICP (Internal Comparison Product). The best performance of semi-transparent coatings in terms of colour retention, adhesion and liquid water absorption showed the cheapest coating system. It has been established that exposure period of 6 weeks was too short to predict performance of opaque coatings. Obtained results could be used as pre-test for natural weathering.

artificial weathering / waterborne coatings / wooden windows 1. INTRODUCTION Wood undergoes dimensional changes when exposed to moisture, it is susceptible to biological attack and it degrades when is exposed to solar ultra violet radiation. These shortcomings have driven many homeowners and builders to switch to other frame materials. To ensure long term performance, in both interior and exterior situations wood needs to be protected by appropriate coating system. All coating systems have numerous properties which must be optimized if they are to perform well. These include drying and recoat times, application, storage characteristics and many others. In addition coatings for wood have a number of special requirements relating to permeability, extensibility, adhesion and fungicidal properties (GRAYSTONE, 1985). It should be emphasized that coating is not designed to correct possible construction failures, but simply to protect wood from moisture and ultraviolet light. Coatings can be divided into water-borne and solvent-borne categories. Waterborne coatings are becoming more popular, partly due to the new environmental rules and partly because of the fact that they are convenient to use. The performance and durability of waterborne coatings are not extensively studied as those of conventional solvent-borne coatings. However, confidence in the durability of waterborne coating materials for wood joinery is the foundation to compete with plastic and aluminium windows that are based on non-renewable resources (DE WINDT et al., 2006). When selecting an exterior wood coating, appearance, durability, cost, surface type, ease of application, and maintenance should be considered (KNAEBE, 1995). The suitability of coating material for a given end-use situation should be confirmed by the appropriate performance test. The traditional way of performing assessment of durability for a coating system is to expose the specimens to natural or artificial climate.

In this paper assessment of durability of semi-transparent waterborne coating systems and opaque waterborne systems with different price tags was performed using artificial weathering method according to HRN EN 927-6. Based on our previous research (JIROUŠ-RAJKOVIĆ et al., 2005; MIKLEČIĆ – JIROUŠ-RAJKOVIĆ, 2011) the most prominent changes during accelerated QUV exposure appeared after 6 weeks, so we wanted find out if it was possible to rank the coatings according to the assessment of coatings performance results obtained after 6 weeks of accelerated weathering.


96

2. MATERIALS AND METHODS

In this study samples of spruce wood (Picea abies L.) free from defects, for the most part of radial texture was used. Four replicate samples of 150x74x18 mm per coating system were prepared in accordance with HRN EN 927-6 for accelerated exposure. Three panels were used for exposure and fourth was unexposed reference. Two replicate samples of 150x70x20 mm per coating system were prepared in accordance with HRN EN 927-4 for water vapour absorption test, and two replicate samples in accordance with HRN EN 927-5 for liquid water absorption test. Coating systems that were tested in this study are used for stable constructions such as windows. Coatings were applied by brush according to manufacture’s instructions. Semi-transparent coating systems AQS and RS had pigment in primer coat, and BS coating system in top coat. Description of the coating systems used is presented in Table 1. Coatings used for the trial were acrylic waterborne dispersion formulated as semi-transparent (AQS, RS, BS) or white opaque stains (AQO, RO, JO). Table 1. Marks and description of coating systems

Mark

Coating system Dry film thickness of coating

system (µm)

Price tag

Primer coat (Impregnation)

Intermediate coat Top coat

Spreading rate

(g/m2)

Number of coats

Spreading rate

(g/m2)

Number of coats

Spreading rate

(g/m2)

Number of coats

AQS 125 1 - - 125 3 132 Low RS 80 1 80 1 90 2 53 High BS 140 1 - - 60 2 46 Medium

AQO 125 1 - - 125 3 73 Low RO 80 1 - - 180 2 91 High JO 80 1 - - 70 2 66 Medium ICP - - - - 50 3 55 Reference

Reference coating (Internal Comparison Product, ICP) is a standardized product for comparison whose composition is specified in annex A of HRN EN 927-3. The ICP is a medium-build, semi-transparent, semi-gloss system based on solvent-borne alkyd technology and in accordance with the procedure described in HRN EN 927-6 ICP must be applied by brushing in three coats with dry film thickness of (50±10) µm. Durability of so applied system in exterior conditions is about 2 years. ICP was produced by Helios factory and it was applied to all sides of four panels and served as a reference coating. The coated samples were exposed for 6 weeks to UV-light, water condensation and water spray in an apparatus with fluorescent lamps (QUV weathering tester). The exposure cycle consisted of 24 hours of condensation followed by a sub-cycle of 2.5 hours of UVA-340 nm and 0.5 hours of water spray as given in Table 2. Table 2. Exposure cycles

Step Function Temperature Duration Condition 1 Condensation (45±3) °C 24 h

2 Sub cycle step 3+4

48 x Cycles of 3 h consisting of steps 3 and 4

3 UV (60±3) °C 2,5 h 0.77 W/(m2nm) at 340 nm

4 Spray 0,5 h 6 l/min to 7 l/min., UV off


97

Before exposure initial measurements of colour, gloss and adhesion were performed. After each cycle of exposure (168 hours) the colour changes was measured and at the end of the 6 weeks exposure period the panels were assessed for cracking (in accordance with ISO 4628-4), gloss, colour and adhesion. The measurement of colour change was made with a portable spectrophotometer Microflash 100d produced by Datacolor (d/8° measuring geometry, 10° standard observer, D65 standard illuminate, xenon flash lamp source) always on the same 6 marked locations on sample. The overall colour change (∆E*) was calculated according to the CIE L*a*b* colour measuring system where, L* describes brightness, a* and b* describe chromatic coordinates on the red-green and yellow-blue axis. ∆E* is the colour difference between the initial colour of the sample and the colour of the sample after exposure and it was calculated using the following formula: ∆E* = [(∆L*) 2 + (∆a*)2 + (∆b*)2]1/2 (1)

where ∆L* describes the difference in brightness (+ light, - dark), ∆a* and ∆b* describes differences in chromaticity coordinates (∆a*: + redder, - greener; ∆b*: + yellower, - bluer). The gloss was measured using portable glossmeter KSJ with 60° measuring geometry on the three locations on sample. The measurement of adhesion was made with cross-cut test according to standard HRN EN ISO 2409. On each sample four measurements were obtained. Assessment of the liquid water and water-vapour absorption was carried out according to standard HRN EN 927-5 and HRN EN 927-4. 3. RESULTS AND DISCUSSION Colour change (∆E*) of wood samples during QUV exposure is presented in Figures 1. All the materials exhibit some initial colour changes during the first week of exposure. The highest initial colour change has uncoated samples (∆E*=19.2) and the lowest opaque coating systems. The colour change of uncoated samples has a different trend during exposure than coated samples, because uncoated samples intensively darken after first week of exposure and then become lighter. During the exposure colour change of semi-transparent coating systems increases during exposure while the colour change of opaque coating systems and ICP coating remain relatively constant during exposure. The colour change of semi-transparent coating systems is higher than colour change of ICP coating, and colour change of opaque coating systems is lower than colour change of ICP coating. After 6 week of exposure the highest colour change is measured on RS coating systems and is 5 times higher than on ICP coating. Colour change is not in correlation with dry film thickness of semi-transparent coating systems, because AQS coating system has the highest and BS coating system has the lowest dry film thickness and both of these systems have the same colour change. As was expected semi-transparent coating systems changed colour more than opaque coating systems. After 6 week of exposure the highest colour changes was obtained for semi-transparent coating system RS, and the lowest for opaque coatings system AQO (Table 3).


98

Figure 1. Colour changes of uncoated and coated samples during accelerated exposure Applying of semi-transparent coating system RS and opaque coating systems RO and JO was a bit more difficult than applying of other coatings systems due to higher viscosity. In Table 3 can be seen that coating systems with higher initial gloss changed gloss more after 6 weeks of exposure. Initial adhesion of all coatings systems was evaluated with grade 2, exceptions were coating system BS with grade 3, and coating system AQO with grade 1. Coating systems AQS-B, RO and JO did not changed adhesion after 6 weeks of exposure, while adhesion of other coating systems reduced for one grade. After 6 weeks of exposure crack on unfinished samples was the largest and visible with the naked eye. On finished samples, only on samples coated with RS coating system appeared cracks visible with magnification (10x). It could be due to the brittleness of intermediate coat (GRAYSTONE, 1985). The most pronounced changes on the surface of samples after 6 weeks of accelerated exposure were colour and gloss changes, and base on these changes the rating of general appearance of samples was made. Table 3. Results of coating systems testing after accelerate exposure

Sample mark

Initial ratings After 6 weeks of exposure

Ease of app.

Gloss Adhesion* Colour change (∆E)

Gloss Adhesion* Numerical cracking ratings*

General appearance according to EN 927-6,

table3* K - 4.5 - 8.8 2.7 - 4 5 AQS Excellent 60.4 2 6.8 26.8 2 0 3 RS Good 22 2 12.2 6.6 3 1 3 BS Excellent 23.7 3 6.6 6 4 0 2 AQO Excellent 64.9 1 1.3 12.1 2 0 1 RO Good 24.8 2 2.1 18.6 2 0 2 JO Good 49.5 2 2 9.2 2 0 1 ICP Excellent 71.1 2 2 2.3 3 0 3 * 0 unchanged, 5 sever, i.e. intense change

The results of the liquid water absorption test show that wood samples finished with coatings systems absorbed less water than unfinished samples (Figure 2a). It can also be seen

a

0

5

10

15

20

168 336 504 672 840 1008

Time of exposure (hours)

Co

lou

r ch

an

ge

, E*

K ICP

AQS BS

RS

b

0

5

10

15

20

168 336 504 672 840 1008

Time of exposure (hours)

Co

lou

r ch

an

ge

, E*

K ICP

AQO JO

RO


99

that liquid water absorption of two semi-transparent coating systems (AQS and RS) is lower than opaque coating systems. Lower liquid water absorption of AQS coating system can be due to the highest dry film thickness, and lower liquid water absorption of RS coating system can be due to adding intermediate coat in coating system. Among all tested coating systems two semi-transparent (AQS-B and RS) and only one opaque coating system (RO) and ICP coating exhibit the value of liquid water permeability lower than 175 g/m2 which is according to HRN EN 927-2 limit value for coatings intended to use for dimensionally stable wood products such as windows and doors (Figure 2a). According to EKSTEDT – ÖSTBERG (2001) the proposed performance specifications in EN 927 - 2 for the water absorption values for coatings to be used in different constructions seem to be set at acceptable levels. There is good correlation between the level of water absorption and practical experience of the performance of the paints in Scandinavia.

Water vapour absorption of BS, AQO and JO coating systems shows smaller deviations in values of unfinished and finished wood surfaces (Figure 2b) which means that the these coating systems less protect wooden substrate from water-vapour absorption and liquid water uptake in the exposures to the high humidity for longer intervals (e.g. in autumn and winter months). On the basis of the results we cannot establish absolute durability of the tested coating systems, but it is possible to compare their performances with reference coating and with each other. The best performance of semi-transparent coatings in terms of colour retention, adhesion and liquid water absorption showed AQS coating system which was the cheapest of the tested semi-transparent coating systems. It has been established that opaque coating systems are hard to ranking after 6 weeks of accelerated exposure. Only RO coating system with highest price meet required performance of water absorption value for dimensional stable wood products.

Figure 2. Liquid water and water vapour absorption of uncoated and coated samples


100

4. CONCLUSION

On the basis of the results we cannot establish absolute durability of tested products, but we can make comparison to the reference coating of known composition (ICP). The problem is that ICP specified in standard HRN EN 927-6 is solvent-borne but most wood coatings are nowadays water-borne. Therefore in the future the new waterborne ICP should be integrated into the standard.

Based on results of water absorption we can conclude that only opaque coating system with high price tag exhibited accepted water absorption value for ”stable constructions”. Semi-transparent coating system with medium price tag did not meet required performance for water absorption.

It has been established that exposure period of 6 weeks is too short to predict performance of opaque coatings.

Based on the overall performance results we can conclude that low price tag of the semi-transparent coating systems does not mean poorer performance. On the contrary, the cheapest coating system performed best after 6 weeks of accelerated exposure.

The artificial weathering could be used for ranking of coating systems performance, but only natural weathering in field tests will gain information about outdoor performance and lifetime expectancy. 5. REFERENCES DE WINDT, I.; COPPENS, H.; VAN ACKER, J. (2006): Performance assessment of coating systems for

exterior wooden joinery. Technological attraction poles, Final report PA-04, project co-ordination H. Coppens, Centre Technique de l’Industrie du Bois, Technisch Centrum der Houtnikverheid, Brussels.

EKSTEDT, J.; ÖSTBERG, G. (2001): Liquid water permeability of exterior wood coatings-testing according to a proposed European standard method. Journal of Coatings Technology 73 (914): pp. 53-59.

GRAYSTONE, J. (1985): The care and protection of wood. ICI Paints Division, Slough. KNEABE, M. (1995): Paint, stain, varnish, or preservative? It’s your choice. A Forest Products

Laboratory finishing factsheet URL: http://www.fpl.fs.fed.us/documnts/finlines/knaeb95b.pdf, 10.6.2013.

JIROUŠ-RAJKOVIĆ, V.; TURKULIN , H.; BORIĆ, D.; PETROVIĆ, M. (2005): Durability of exterior wood coatings. In Proceedings of the 7th International conference on wood technology, construction industry and wood protection under motto “Durability and quality of structural wood products”. Croatia, Zagreb. April, 2005. pp. 63-69.

MIKLEČIĆ, J.; JIROUŠ-RAJKOVIĆ, V. (2011): Accelerated weathering of coated and uncoated beech wood modified with citric acid. Drvna Industrija 62 (4): pp. 277-282.


101

Numerical Analysis of Laminated Wood Structures - Chairs by Application of FEA

NESTOROVIĆ Biserkaa*– GRBAC Ivicab – NESTOROVIĆ Predragc

a University of Belgrade Faculty of Forestry, Belgrade Serbia b University of Zagreb Faculty of Forestry, Zagreb, Croatia

c University of Belgrade Faculty of Architecture, Belgrade, Serbia *Corresponding author: [email protected]

Abstract – Models of the chair structure of laminated wood are presented in this paper for the cases of suspension on four and two legs - cantilever chair. All numerical analysis are done by application of quadrilateral finite plate and shell element for the case of composite. Modeling of the edge supports of cantilever chair, which basically represents a beam laminated element, is done by composite plate element in software package KOMIPS. However, the obtained results are very reliable considering that sufficiently dense mesh was adopted, which problem of the beam subjected to the banding in its plane reduces to the analysis of set of small plate elements.

FEA / laminated wood / chairs 1. INTRODUCTION

1.1. Wood laminated specimens

Obtained numerical results by application of software package REDKRUT and experimental analysis of wood laminated specimens E 2.1.1 and E 2.2.1 are shown in the Figure 1 and Figure 2. It could be noticed that they show a very good compliance with the experimental values. Composite t = 8 x 1,5 = 12.0 mm, 0/0/0/0 / 0/0/0/0 (lamina orientation in specimen) Specimen dimensions are 30x250 mm.

ΣF = 10000 N

fmax = 0,21 mm , σmax

ekv = 27,8 Mpa

Figure 1. Computer simulation of the experimental analysis of wooden specimen E 2.1.1

Composite t = 8 x 1,5 = 12.0 mm, 90/90/90/90 / 90/90/90/90 (lamina orientation in specimen) Specimen dimensions are 30x250 mm

ΣF = 1000 N

fmax= 0,167mm , σmax

ekv = 2,78 Mpa

Figure 2. Computer simulation of the experimental analysis of wooden specimen E 2.1.2


102

2. WOOD LAMINATED CHAIR STRUCTURE

Models of chair structure made of laminated wood are shown in the Figure 3 for the case of the rest on four legs and Figure 6 for the rest on two legs (cantilever chair). 2.1. Model of the chair rested on the four legs

Material characteristics of lamina are given in the following tables and the results of the stress and strain analysis are shown in the Figure 4 for the case of vertical and in the Figure 5 for the case of vertical and horizontal load.

Figure 3. Layout of the chair rested on four legs

Composite: t1 = 17x1,2 = 20,4 mm , 0/0/0/0/0/0/0/0 /0/ 0/0/0/0/0/0/0/0 - longitudinal and transversal beams. Table 1. Elasticity matrix for massive lamina

ELASTICITY MATRIX FOR MASSIVE - LAMINA Q[MPa] 1,1 1,2 1,6 2,2 2,6 6,6 QD(i,j) 1.76E+04 9.730E+02 0.000E+00 2.14E+03 0.000E+00 1.15E+03

Composite t = 8 x 1,2 = 9,6 mm 0/90/0/90 / 90/0/90/0 (lamina orientation in specimen)

Table 2. Material properties

LAYER PROPERTIES H1 H2 E11/Q11 E22/Q12 Ni12/Q16 0/Q22 0/Q26 G12/Q66 Teta 4.8 3.6 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 3.6 2.4 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 2.4 1.2 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 1.2 .0 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 .0 -1.2 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 -1.2 -2.4 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 -2.4 -3.6 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 -3.6 -4.8 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00

REDUCED STIFFNESS OF LAMINATE 1,1 1,2 1,6 2,2 2,6 6,6 A(i,j) 9.5270E+04 9.3408E+03 0.0000E+00 9.5270E+04 0.0000E+00 1.0032E+04 B(i,j) 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 D(i,j) 9.4540E+05 7.1737E+04 0.0000E+00 5.1796E+05 0.0000E+00 7.7046E+04

LAMINATA REDUCED ELASTICITY MATRIX OF LAMINATE 1,1 1,2 1,6 2,2 2,6 6,6 QA(i,j) 9.9240E+03 9.7300E+02 0.0000E+00 9.9240E+03 0.0000E+00 1.150E+03 QB(i,j) 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 QD(i,j) 1.2823E+04 9.7300E+02 0.0000E+00 7.0252E+03 0.0000E+00 1.150E+03


103

Figure 4. Reduced stiffness – the first load case

For the first load case stress concentration is maximal in the central area of the seat and is

5,18 MPa, compared to the maximal fracture stress obtained experimentally for banding of 89,95 MPa.

Figure 5. Reduced stiffness – the second load case

In the second load case maximal stress is 16 MPa, and is in the curved part of transition

between back and seat, however its values are far below the boundary fracture stress σfx.

2.2. Model of the chair rested on two legs (cantilever chair)

Three load cases were analyzed: horizontal load on the chair back with and without seat, and load by vertical force on the chair seat.

The chair rested on two legs Figure 6 subjected to bending by the action of horizontal concentrated force of 100 N at the top of the back is analyzed for the case of the entire structure, with the elements of plate for seat and backrest as well as for the case without these elements. The results of the analysis of the first load case include both real and reduced stiffness of the laminate are shown in the Figure 7.

Figure 6. Layout of the chair rested on two legs - cantilever chair and the way of load


104

Composite : t1 = 23x1,2 = 27,6 mm , 0/0/0/0/0/0/0/0/0/0/0/0 /0/ 0/0/0/0/0/0/0/0/0/0/0/0 - longitudinal beams Composite: t2 = 15x1,2 = 18 mm , 0/0/0/0/0/0/0 /0/ 0/0/0/0/0/0/0 - transverse beams Table 3. Elasticity matrix for massive lamina

ELASTICITY MATRIX FOR MASSIVE - LAMINE Q[MPa] 1,1 1,2 1,6 2,2 2,6 6,6 QD(i,j) 1.76E+04 9.730E+02 0.000E+00 2.14E+03 0.000E+00 1.145E+03

Composite: t3 = 12 x 1,2 = 14,4 mm, 0/90/0/90/0/90 / 90/0/90/0/90/0 (lamina orientation) Table 4. Material properties

LAYER PROPERTIES H1 H2 E11/Q11 E22/Q12 Ni12/Q16 0/Q22 0/Q26 G12/Q66 Teta 7.2 6.0 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 6.0 4.8 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 4.8 3.6 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 3.6 2.4 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 2.4 1.2 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 1.2 .0 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 .0 -1.2 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 -1.2 -2.4 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 -2.4 -3.6 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 -3.6 -4.8 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 -4.8 -6.0 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 -6.0 -7.2 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00


LAMINATA REDUCED ELASTICITY MATRIX OF LAMINATE 1,1 1,2 1,6 2,2 2,6 6,6 QA(i,j) 9.9240E+03 9.7300E+02 0.0000E+00 9.9240E+03 0.0000E+00 1.0450E+03 QB(i,j) 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 QD(i,j) 1.1856E+04 9.7300E+02 0.0000E+00 7.9915E+03 0.0000E+00 1.0450E+03

Composite: t4 = 8x1,2 = 9,6 mm 0/90/0/90 / 90/0/90/0




REDUCED ELASTICITY MATRIX OF LAMINATE 1,1 1,2 1,6 2,2 2,6 6,6 QA(i,j) 9.9240E+03 9.7300E+02 0.0000E+00 9.9240E+03 0.0000E+00 1.150E+03 QB(i,j) 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 QD(i,j) 1.2823E+04 9.7300E+02 0.0000E+00 7.0252E+03 0.0000E+00 1.150E+03


105

Figure 7. Reduced stiffness - first load case

The critical load is in the lower arched part of the chair leg of 6,79 MPa compared to the fracture stress which is σfx = 134,78 MPa, multiply over dimensioned.

In Figure 8 is given the model of the edge girders. Load and strain state is given in Figure 9, and stress cahnge is given in the Figure 10.

Figure 8. Model of edge supports of the chair second load case

Composite: t1 = 23x1,2 = 27,6 mm , 0/0/0/0/0/0/0/0/0/0/0/0 /0/ 0/0/0/0/0/0/0/0/0/0/0/0 - longitudinal beams. Composite: t2 = 15x1,2 = 18 mm , 0/0/0/0/0/0/0 /0/ 0/0/0/0/0/0/0 - transverse beams. Table 6. Elasticity matrix for massive lamina


Figure 9. Load and strain model of the chair with edge girders; Figure 10. Stress state of the chair

with edge girders


106

Chair loaded in the same way as the previous one without seat plate, shows a high concentration of the stress in the part of the seat on the composition of horizontal beams and legs, visually observed as dense disposition of isocurves of equivalent stress, which should be avoided, although the maximum stress values are hear small.

The third model of the chair with edge girders and plates with continuous-loaded seat (replaced by concentrated forces) is shown in Figure 11. Numerical computation by finite elements is verified via deflection experimentally. Laser deflection meter is placed in the middle of the span, below the lower binder which connects chair legs.

Figure 11. Layout of cantilever chair for the third load case

In the experiment, on the seat of the chair the weight of mass ΣF=700 N was placed. The

finite element mesh of this model with the numbers of nodal points and the numbers of finite plate elements is shown in the Figure 12 and Figure 13. and pointed stress and strain images Figure 14 and Figure 15.

Figure 12. Labeling of the nodes by finite elements; Figure 13. Labeling of surfaces by finite elements

The calculation was prepared and completed as follows: Laminate: t1 = 23x1,2 = 27,6 mm , 0/0/0/0/0/0/0/0/0/0/0/0 /0/ 0/0/0/0/0/0/0/0/0/0/0/0 - longitudinal beams. Laminate: t2 = 15x1,2 = 18 mm , 0/0/0/0/0/0/0 /0/ 0/0/0/0/0/0/0 - transverse beams. Table 7. Elasticity matrix for massive lamina


Laminate: t3 = 12x1,2 = 14,4 mm 0/90/0/90/0/90 / 90/0/90/0/90/0 - backrest.


107


LAYER PROPERTIES H1 H2 E11/Q11 E22/Q12 Ni12/Q16 0/Q22 0/Q26 G12/Q66 Teta 7.2 6.0 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 6.0 4.8 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 4.8 3.6 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 3.6 2.4 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 2.4 1.2 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 1.2 .0 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 .0 -1.2 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 -1.2 -2.4 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 -2.4 -3.6 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 -3.6 -4.8 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00 -4.8 -6.0 2.14E+03 9.73E+02 0.00E+00 1.76E+04 0.00E+00 1.15E+03 9.00E+01 -6.0 -7.2 1.76E+04 9.73E+02 0.00E+00 2.14E+03 0.00E+00 1.15E+03 0.00E+00



Laminate: t4 = 8x1,2 = 9,6 mm 0/90/0/90 / 90/0/90/0 - seat





Figure 14. Strain for the third load case; Figure 15. Reduced stiffness third load case


108

The maximal deflection of 43,2 mm refers to the backrest of the chair. Deflection obtained numerically above the laser meter was 12,5 mm. Experimental average deflection values were measured for 5 chairs, and were as follows: 11,5; 11,6; 11,4; 11,5 and 11,6 mm. It can be concluded that experimental measurements confirmed the numerical calculation. Layout of the model of cantilevered chair was given in the Figure 6. The pneumatically load of the chair seat is given in the Figure 16, the initial measurement of deflection of the relieved cantilever chair by laser meter was given in the Figure 17, the measurement of deflection by laser meter under vertical load of chair seat was given in the Figure 18, determination of the horizontal force on the backrest of the chair by dynamometer is given in the Figure 19. The maximum stress is also on the lower and upper part of the arch of the chair leg and is 9,85 MPa.

Figure 16. Pneumatically load on

the seat of cantilever chair Figure 17. Relieved cantilever chair with measurement of deflection by laser meter

Figure 18. Measurement of deflection by

laser meter under vertical load on the seat of cantilever chair by weight of 700 N

Figure 19. Determination of the horizontal force on the backrest of the

chair by dynamometer

The obtained numerical results for the case of geometrically free-form shell (seat with beck) and the entire structure with the elements of the plates for seat and back rested on two legs has been confirmed experimentally on the real cantilever chair, and deflection was fmax = 12,5 mm.

3. CONCLUSION

Conducted research within the framework of theoretical, experimental and numerical part and introduction of reduced stiffness of complex laminate in finite elements, along with experiments with chairs, which were done with the objective of determination of stiffness of such systems by measurement of real displacements on selected models, confirm numerical calculation. Previously enables design, redesign, construction and dimensioning not of only


109

chairs but any beam or surface system on the base of laminate, with the posibility of material variation, combination of different materials, leyet thickness and fiber orientation.

Acknowledgements: Authors are supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, Project No. TP 36008. 4. REFERENCES NESTOROVIĆ, B. (2010): Istraživanje i analiza čvrstoće nameštaja za sedenje izgrađenog od laminata

na bazi drveta. Doktorska disertacija. Univerzitet u Beogradu, Šumarski fakultet: pp. 101-118. MANESKI, T. (1998): Kompjutersko modeliranje i proračun struktura. Mašinski fakultet Univerziteta u

Beogradu, br. 8, Beograd.


111

The Impact of Wood Staining on the Adhesion of Certain Types of Coating

PALIJA Tanjaa*– VUČKOVIĆ Aleksandara – JEVTIĆ Petronijeb – JAIĆ Milana a Technology, Management and Design of Furniture and Wood Products, Faculty of Forestry, University of

Belgrade, Belgrade, Serbia b Graduate School of Applied Professional Studies, Vranje, Serbia


Abstract – This paper investigates the impact of the staining of spruce wood (Picea Abies Karst.) on the adhesion of different types of coating. The samples were stained with water-based stain and lacquered using three types of transparent coatings: nitrocellulose (NC), polyurethane (PU) and water-based coating (WB). Since the water from the stain leads to swelling of wood tissue and an increase of roughness in the surface layer, surface roughness of wood was measured before and after staining and related to the adhesion of coatings. Among unstained samples, the highest values of adhesion (4.50 MPa) was obtained in samples lacquered with WB coating, fallowing by samples lacquered with PU coating (3.72 MPa) and samples lacquered with NC coating (2.43 MPa). Staining of wood had a negative impact on the value of adhesion in the case of WB coating (4.11 MPa). The increase in surface roughness as a result of staining had a positive impact on the value of adhesion for samples which were lacquered with PU coating (4.87 MPa). The samples which were stained and lacquered with NC coating showed a slight increase in adhesion value compared to samples lacquered with same type of coating without staining (2.74 MPa).

spruce wood / staining / surface roughness/ coating / adhesion 1. INTRODUCTION Stains represent the dispersion of pigments or dyes in an appropriate solvent. Staining procedure can change the natural colour of the wood while preserving its texture. In order to protect the wood from the negative effects of environmental factors and to preserve obtained colour of wood, it is necessary to lacquer wood with transparent coating after staining. Application of water-based stains is environmentally justified, since working environment is free from vapours of organic components in to the air. In addition, water-based stains are non-flammable and non-hazardous (CHARRON, 1998). Application of these stains gives the vibrant colour tones and uniformity of colour over the surface thanks to the great depth of water penetration into the substrate. However, the use of water-based stains has its disadvantages. First, the wood swells in contact with water. After staining, the water evaporates from the surface of wood causing the wood fibres to raise and bend which leads to an increase in surface roughness (JAIĆ – ZIVANOVIC -TRBOJEVIĆ, 2000). The increase in roughness can have a negative impact on the aesthetic quality of lacquered surfaces, as glow is a function of the surface roughness. In addition, with the increase in the surface roughness the contact area between the substrate and the coating increases as well. Knowing the different mechanisms of adhesion of the coating to the wood substrate, the increase in roughness can have a different impact on the value of adhesion of different types of coating. Generally, higher values of adhesion between the coating and the substrate are expected if the surface is roughened before lacquering (WICKS et al., 2007; RIZZO – BRUNO, 2009). On the other hand, previous studies have shown that the increase in roughness expressed as parameters Sa

1, which occurred as a result of sanding with sanding belts with different grits, has no significant impact on the adhesion of samples lacquered with water-based coating (COOL – HERNANDEZ, 2011). In examination of the effect of different treatments of spruce

1 The arithmetical mean deviation of the profile


112

wood before lacquering with NC coating on the values of adhesion, no correlation between the roughness of the surface which is caused by treatment with the stains, bleaching agents and preservatives and adhesion values was found (OZDEMIR – HIZIROGLU, 2007). Based on this result it can be concluded that the increase in roughness cannot be considered separately from the material by which this effect is achieved.

The aim of this paper is to investigate the impact of staining of wood by water-based stain on the value of the adhesion of the three most commonly used coatings in the wood industry: nitrocellulose (NC), polyurethane (PU) and water-based (WB) coating. As high values of other mechanical properties of lacquered surface have little significance if adhesion between the coating and the substrate is disrupted (RIZZO – BRUNO, 2009), testing of the adhesion of coating on previously treated wood gets even more importance. Since it is believed that the optimal method for determination of coating adhesion is combination of direct adhesion measuring methods and characterization of substrate surface (AWAJI et al., 2009), geometrical state of wood surface and adhesion measurements were conducted in this research. 2. MATERIALS AND METHODS 2.1. Choice of substrate

Spruce (Picea Abies Karst.) is known as the wood species of a small density, low permeability, and high volume porosity (72 % according to ŠOŠKIĆ et al., 2007). During the drying process pits between transports elements became closed, which leads to decrease in permeability of wood tissue, which may affect the penetration of the coating into the substrate (GINDL et al., 2006). Lower depth of penetration of coatings leads to decrease of contact area between the coating and the substrate, which may affect the value of adhesion (MEIJER et al., 1998). In addition, the porosity of the wood is considered as one of the significant factors that affect the value of adhesion (SONMEZ et al., 2009; OZDEMIR – HIZIROGLU, 2007). Previous studies had shown that compared with higher density wood species, samples of spruce wood will have lower value of adhesion (JAIĆ – PALIJA , 2012). For this research, 12 samples of spruce wood with dimensions of 400×100×20 mm were used. Spruce samples were prepared by sanding on narrow-belt sander with manual pressure control (MiniMax L55) in a three-stage grit system: N˚ 80, N˚ 120 and N˚ 180. Sanding speed was 19 m/s. The moisture content of spruce samples was measured by hydrometer (NIGOS DVD-240). For each sample moisture content was measured at two positions. After sanding, one-half of all samples was stained by applying water-based stain (025 AC Colorata VERINLEGNO) by air-spraying in a chamber with controlled conditions of the working environment (t = 20±2 °C, φ = 50±5 %). The spraying pressure was 3.5 bars, and nozzle diameter of spray-gun was 1.8 mm. To examine the effect of staining on the adhesion of different types of coating one-third of all samples was lacquered with 1K NC coating (NF VERINLEGNO 50), second-third with 2K PU coating (VF A TX 2019 E VERINLEGNO) and the last-third with 1K water-based coating (200 IDROFOND TX INT VERINLEGNO). All of coatings were transparent. The scheme of surface finishing treatment by groups of samples is given in the Table 1.

Table 1. Scheme of the surface finishing treatment of samples by groups

Serial number of the sample group Treatment 1 2 3 4 5 6 Water-based stain * * * NC coating * * PU coating * * WB coating * *


113

All coatings were applied to the surface of control (non-stained) and stained samples by air-spraying process in a single coat in the same working environment conditions as for staining. Spraying pressure was 3.5 bar, and the distance between spay-gun and sample 20 cm. The nozzle diameter of spray gun for NC, PU and WB coatings were: 1.8 mm, 1.8 mm and 2.2 mm, respectively. Technical characteristics of applied stain and coatings are given in Table 2.

Table 2. Technical characteristics of the water-based stain and NC, PU and WB coating

Material Water-based stain NC coating PU coating WB coating Density (kg/m3) 0,980±1 % 0,950±1 % 0,970±1 % 1,020±1 % Added diluents (%) 20-30 20-40 0-10 Viscosity (20 °C) 12 ±1 s (DIN 4) 15-20 s (DIN 4) 14-16 s (DIN 4) 30-50 s (DIN6) Solid content (%) 11±1 % 21-23 38-42 32-34 Application rate (g/m2) 50-80 120-180 120-150 120-150

2.2. Determination of the geometric state of wood surface

The characterization of the substrate before and after staining was performed by determining roughness parameter Ra by contact-mechanical roughness tester (TR200, manufacturer Beijing TIME High Technology Ltd.), in accordance with ISO 4288: 1996. Determination of roughness parameters is based on the movement of 2 µm-radius diamond tip stylus at 90˚ angle to the surface of the wood. During the movement the force of 4 mN ensures constant contact of the stylus tip and on the surface of the sample. Vertical movement of the stylus tip is transformed into an electrical signal that is filtered and translated into the value of parameter Ra. The parameter Ra was measured in the transverse and longitudinal direction relative to the direction of wood fibres (Figure 1). For each group of samples 9 measurements were performed, and the result is presented as the mean value of measurements in transverse and longitudinal direction.

Figure 1. Determination of the parameter Ra after sanding parallel to the wood fibres

2.3. Determination of the dry film thickness of the coating

Dry film thickness of the coating was determined by modern non-destructive method using an ultrasound gauge (POSITector 200, DeFelsko), in accordance with EN ISO 2808: 2011. The principle of determining the thickness of the coating is based on the measurement of time needed for ultrasonic waves, emitted from the surface of the probe, to pass through the coating to the surface of substrate and same path back to the transducer. Knowing that there is unevenness on the surface of the coating that can cause the errors in the reading, drop of gel (water-glycerine-based) was placed on the coating, filling the irregularities on the surface of the coating. Thickness of the coating was obtained as the mean value of 8 measurements for each group.


114

Figure 2. Measurement of the dry film thickness of the coating

2.4. Determination of the adhesion of coating

2.4.1. Determination of adhesion of coating by cross-cut test

Determination of the adhesion of coatings by cross-cut test (by Paint Inspection Gauge121/4, manufacturer Elcometer) was conducted in accordance with EN ISO 2409: 2010.The principle of determination of the adhesion is based on the evaluation of the resistance of the coating to the indentation. Firstly, six parallel cuts were made at lacquered surface at 45˚ angle relative to the direction of wood fibres. Afterwards, the six more cuts were formed at 90˚ angle to the first cut, forming lattice pattern on the coating. Evaluation of the coating adhesion was made by appearance of the lattice. Lowest evaluation mark (0) means that the edges of the cuts are completely smooth; while the highest mark (5) means that the lattice is severely damaged. The blades are set at a distance of 3 mm, which is consistent with the measured dry film thickness of coatings. To obtain valid results, it is necessary for the blades to penetrate to the surface of the substrate. By applying the ink on surface of formed lattice, the depth of blade penetration was determined (Discoloration of wood beneath the lattice lines is the proof of the blade penetrating the surface of the substrate). The total number of adhesion measurements was18 (three measurements for each group of samples). In Figure 3 cross-cut test instrument is shown.

Figure 3. Determination of adhesion of coating by cross-cut test

2.4.2. Determination of the adhesion of coating by pull-off test

Determination of the adhesion of the coating by pull-off test was performed according to the EN ISO 4624: 2005 (using PosiTest AT-A instrument, manufacturer DeFelsko). Pull-off test is destructive method for determining tensile strength of wood coatings. Tensile strength is calculated as the ratio of pulling force that leads to the detachment of the coating from the surface of the wood and the surface to which the pulling force is applied. The instrument consists of a housing containing the hydraulic pump and the actuator, which is connected to the housing by cable. The pulling force was applied to coating via 20-mm diameter aluminium dollies that were glued to the lacquered surface with 2K epoxy adhesive (ARALDITE 2001, Huntsman). The measuring principle involves cleaning the surface of dollies to provide a clean and flat surface, i.e. to remove impurities from the surface that may have an


115

impact on the value of adhesion, and gluing of cleaned dollies to the lacquered surface. After curing of adhesive (24 hours), the pulling force was measured. In order to obtain accurate data, area under dollies was separated from the rest of the lacquered surface by circular groove, which is formed by a cylindrical cutting tool. This way, the pulling force was limited solely on the coating underneath the dollies. The total number of measurements was 60 (10 measurements for each group of samples). Figure 2 shows the equipment for measurement of the adhesion by pull-off test.

Figure 4. Measurement of adhesion of coating by pull-off test

3. Results and Discussion

The average moisture content of spruce samples before staining and lacquering was 9.04 %. The average surface roughness after sanding of the samples expressed as parameter Ra perpendicular to the wood fibres was 3,426 µm and 2,552 µm parallel to the wood fibres. The small difference in the value of the parameter Ra perpendicular and parallel to the wood fibres can be explained by the high value of the reference length. Both early and late wood were included in observing length, so the surface roughness parallel to the wood fibres could not be measured precisely.

Staining of spruce wood with water-based stain led to an increase in surface roughness for 33.65 % perpendicular and 40.92 % parallel to wood fibres

In Figure 5 increase of roughness of wood after staining perpendicular (a, c, e) and parallel (b, d, and f) to the direction of the wood fibres is shown graphically.

a) b)

33,5

44,5

5

1 2 3 4 5 6 7 8 9

Sur

face

rou

ghne

ss[µ

m]

Number of measurement

before staining after staining

1,5

2,5

3,5

4,5

1 2 3 4 5 6 7 8

Sur

face

rou

ghne

ss[µ

m]


before staining after staining


116

c) d)

e) f)

Figure 5. Surface roughness before and after staining perpendicular to the wood fibres: a) Group 4; c) Group 5; e) Group 6 and parallel to the wood fibres b) Group 4; d ) Group 5; f) Group 6.

Average dry film thickness of the coating of control and stained samples is given in Table 2.

Table 3. Average dry film thickness of the coating of control and stained samples lacquered with NC, PU and WB coating

Type of coating NC PU WC BNC BPU BWB Average dry film thickness (µm) 61,44 74,63 50,44 61,06 68,88 58,63

The mean values of adhesion of control and stained lacquered samples measured by cross-cut and pull-off test are given in Table 3.

Table 4. Mean values of adhesion of control and stained samples lacquered with NC, PU and WB coating

Type of coating Type of test NC PU WB BNC BPU BWB Cross-cut test 1,67 1 1 2 1 2 Pull-off test (MPa) 2,43 3,72 4,50 2,74 4,87 4,11

Comparing the results of adhesion by cross-cut and pull-off test it can be concluded that it is necessary to include more than one method in the evaluation of adhesion in order to obtain realistic view of this property. The lowest adhesion values measured by pull-off test registered on the samples coated with NC coating, with (2.74 MPa) or without staining (2.43 MPa), were also rated with lower grade (mark 2) in cross-cut test, in comparison to other samples. Also, samples that showed the highest tensile strength: BPU (4.87 MPa) and WB (4.50 MPa) obtained the highest marks for resistance to indentation when cutting the coating in the form of lattice (Grade 1). In samples that were stained and lacquered with WB coating there were significant disagreement of the adhesion results measured with cross-cut and pull-off method.

2,5

3,5

4,5

5,5

1 2 3 4 5 6 7 8 9Sur

face

rou

ghne

ss[µ

m]


1,5

2,5

3,5

4,5

1 2 3 4 5 6 7 8 9Sur

face

rou

ghne

ss[µ

m]


33,5

44,5

55,5

6

1 2 3 4 5 6 7 8 9

Sur

face

rou

ghne

ss[µ

m]


1,52

2,53

3,54

4,5

1 2 3 4 5 6 7 8S

urfa

ce r

ough

ness

[µm

]Number of measurement


117

The values of tensile strength of these samples are slightly lower than the value of adhesion of BPU and WB samples, which obtained mark 1 in cross-cut test. Also high grade of adhesion measured in cross-cut test of samples lacquered with PU coating is not consistent with the significantly lower measured values of tensile strength of the same samples.

The value of adhesion of spruce samples lacquered with NC coating was in accordance with the results of previous studies of the same type of coating on samples of the same wood species (2.56 MPa at 8 % moisture content according to Sonmez et al., 2009). In the same research, the adhesion value of the samples of spruce wood lacquered with 2K PU coating was higher (4.436 MPa), and for samples lacquered with WB coating was lower (3.373 MPa) compared with the value of adhesion on samples lacquered with these types of coatings in our research. It should be note that in the above mentioned research the samples were lacquered by applying two coats of the appropriate type of coating.

The increase in surface roughness of wood by 33 % after staining resulted in increased adhesion of NC coating by 12.9 %. For samples that were lacquered with PU coating increase of wood roughness after staining by 39 % led to an increase in the adhesion by 31 %. Only in the sample lacquered with water-based coating increase of wood roughness after staining by 43.2 % led to reduce of adhesion by 8.7 %. Decease of adhesion of WB coatings after staining is consistent with the conclusion that the higher values of adhesion of WB coatings can be achieved when the wood surface is smoother (LANDRY – BLANCHET, 2012).

4. CONCLUSIONS

Based on this research we can conclude the following: • The formulation of the coating affects the value of the adhesion of coatings on the

wood surface. • Staining of spruce wood with water-based stain led to an increase in surface

roughness. Staining of wood led to increase of surface roughness which had positive impact on the value of the adhesion of the samples lacquered with NC and PU coating. For samples that were lacquered with water-based coating, staining followed by increased surface roughness had negative impact on adhesion. ACKNOWLEDGEMENTS: This paper was realized as a part of the project Establishment of Wood Plantations Intended for the Afforestation of Serbia (31041) financed by the Ministry of Education, Science and Technological of the Republic of Serbia within the framework Technological development for the period 2011-2014. 5. REFERENCES AWAJA, F.; GILBERT, M.; KELLY , G.; FOX, B.; PIGRAM, P. (2009): Adhesion of polymers. Progress in

Polymer Science 34, Elsevier, Amsterdam, pp. 948-968. CHARRON, A. (1998): Stains and Dyes. In: Water-based finishes, The Taunton Press, pp.67-85. COOL, J.; HERNANDEZ, R. (2011): Improving the Sanding Process of Black Spruce Wood for Surface

Quality and Water-Based Coating Adhesion. 61 (11): pp. 372–380. EN ISO 2808 (2007): Paints and varnishes -- Determination of film thickness. GINDL, M.; SINN, G.; STANZL-TSCHEGG, S. (2006): The effects of ultraviolet light exposure on the

wetting properties of wood. Journal of Adhesion Science and Technology 20 (8): pp. 817-828. ISO 4288 (1996): Geometrical Product Specifications (GPS) -- Surface texture: Profile method --

Rules and procedures for the assessment of surface texture. JAIĆ, M.; PALIJA, T. (2012): Uticaj vrste drveta i sistema površinske obrade na adheziju premaza.

Zaštita materijala 53 (4): pp. 299-303.


118

JAIĆ, M.; ŽIVANOVI Ć-TRBOJEVIĆ, R. (2000): Materijali za površinsku obradu drveta. In: Površinska obrada drveta, Autorsko izdanje, Beograd, pp.39-90.

LANDRY, V.; BLANCHET, P. (2012): Surface Preparation of Wood for Application of Waterborne Coatings. Forest products journal 62 (1): pp. 39-45.

MEIJER, M.; THURICH, K.; MILITZ , H. (1998): Comparative study on penetration characteristics of modern wood coatings. Wood Science and Technology 32: pp.347-365.

OZDEMIR, T.; HIZIROGLU, S. (2007): Evaluation of Surface Quality and Adhesion Strength of Treated Solid Wood. Journal of Materials Processing Technology 186 (1-3): pp. 311–314.

RIZZO, М.; BRUNO, G. (2009): In: Surface Coatings, Nova Science Publishers Inc., New York, pp. ŠOŠKIĆ, B.; GOVEDAR, Z.; TODOROVIĆ, N.; PETROVIĆ, D. (2007): Basic physical properties of Spruce

wood (Picea abies Karst.) from plantations. Bulletin of the Faculty of Forestry 96: pp. 97-110. SRPS EN ISO 2409 (2010): Paints and varnishes -- Cross-cut test. SRPS EN ISO 4624 (2005): Paints and varnishes -- Pull-off test for adhesion. WICKS, Z.; JONES, F.; PAPAS, P.; WICKS, D. (2007): Adhesion. In: Organic Coatings: Science and

Technology, Third Edition, Jonh Wiley and Sons, Inc., New Jersey, pp.121-125.


119

On Enhancing of Production Planning in Wood Processing and Furniture Manufacturing

PERIĆ Ivanaa – GRLADINOVIĆ Tomislava*– STARČEVIĆ Igorb – STASIAK-BETLEJEWSKA Renatac

a Wood Technology Department, Faculty of Forestry, University of Zagreb, Zagreb, Croatia

b Lesnina d.o.o., Zagreb, Croatia c Institute of Production Engineering, Faculty of Management, University of Technology, Poland


Abstract – The importance of planning cannot be stressed enough. By analysing the company and its future operations objectively, one reveals its strengths and weaknesses, recognises potential hazards, discovers new revenue opportunities and achieves planned business objectives. Planning helps in detecting problems early, discovering their causes and finding an efficient solution, and also allows to avoid completely some problems while they are still small. This paper examines the ways and methods of production planning in wood processing and furniture manufacturing. With the aid of available literature, a detailed planning process is demonstrated, covering the topics such as management, control and planning with their respective roles, goals and purpose, as well as environment-dependent dynamic planning. The planning theory is compared to the practice to underline commonly encountered problems.

planning process / regulation of planning time / process management / planning preparation

1. IDEA OF PLANNING AND SYSTEM OF PLANNING

Planning is defined method of forming desires; the opposite of panning is improvisation. It is thinking ahead. Planning definition in functional sense is that planning is sententious preparation of future activities, methodological-systematically process of cognition and solving future problems, perspective sententious activity which determines future activities ahead. Planning is a process of determining what organisation wants to achieve and deciding how to achieve those goals.

It includes: prediction on possible environment constellation and achievable way of acting in future period and determining ways of acting for achieving given planned goals in accordance with management philosophy.

One of the most important entries of planning is focus on the future. However, like planning, prognoses are also focused on future. While planning determines which decisions should be brought in order for future actions to occur, prognosis predicts future actions that will probably occur. Thereby, prognosis is necessary and very important part of decision process. However, in contrary to planning, prognosis is not active function; it is one of planning methods.

1.1. Function, purpose and goals of planning

Planning as controlling tool has a special role in wood manufacturing and wood processing companies (GRLADINOVIĆ, 1999). It contributes to important goals achievement, important measures undertaking, design and evaluation of expectations and attitude, work and response and contact improvement inside the company. Basic functions of planning are:

success insurance, that is efficiency growth due to resources and goals planning risk cognition and reduction with the help of anticipative analysis and solving future

problems flexibility growth considering, for example, creation and assurance of future work

space


120

complexity reduction, for example, by establishing alternative future actions and excluding certain situations and events

creating synergetic effects, for example, inside boundaries of individual measures dependence cognition.

The purpose of planning is in excluding unexpected events probability decrease, in order to minimise chosen measurement risk. Basic guidance idea of properly understood business planning is that planning is a learning process, and deviations are accepted as its definite component.

Central goal of planning in company concerns two problems field control, whose importance for business management constantly grows due to:

constant adjustment needs: because of fast changes in numerous social, technical and economical dimensions, probability of unexpected events and amplified complexity in company is increased; generally growing dimension of company and diversification of products and market demand new business structures.

It is considered that the basic elements of planning are: goals – what? premises – under what conditions? problem – why? measures – how? resources – what with? terms – when? carriers – who? results – what are the effects? Considering the period of planning we can speak of time dimension between horizon and

point of planning. We can distinguish: long term planning, for period longer than 5 years; medium term planning, for period between 2 and 5 years; and short term planning, for period until one year.

1.2. Objects of planning

It is generally considered that the objects of planning can be: building businesses which include building companies in organisational, technical and financial sense; business program, which is product program for determined period; and company business, which is mutual adjustment and exploitation of production factors, and depending on business process phase it is separated on planning of acquisition, sale etc. (GRLADINOVIĆ, 1999).

Objects or matters of planning can be all objects of business activity. The following classifications contribute to object planning clearness:

periodicity: there is one-time planning (planning of formation, location etc.), occasional planning (planning of merging, sanitation, stocks) and permanent planning (planning of production, sales etc.)

maturity: short term, medium term and long term needs and needs cover: according to this criteria needs are planned and faults are

determined, then, by needs cover planning those faults are removed planning process content: this aspect relies on planning process phases – goal

planning, activity planning, measures planning and resources planning business fields: planning of sale, production, finances, investments and employment

are basic fields of planning companies.


121

2. OPERATION PLANNING – FUNCTION AND INSTRUMENTS 2.1. Planning process

Planning is sententious process of forming future, it is the process of sententious progression in future possibilities, and thus it is in fact spiritual process. Planning process can be defined as goal focused, chained sequence of individual information transforming activities with certain goal. Planning process is observed as specific decision making process, specific because it relates to future (SUJOVÁ, 2004). According to phase theorem, basic phases of decision making process are: problem identification, information search, formation of alternative decision making, alternative evaluation, choosing alternative and decision conduction.

Simplified, we can talk only of four process phases: problem definition, solution detection, optimisation and implementation.

Planning process occurs through certain stages, in first stage goals are defined (what is wanted) in second stage they are measured and paths (how is it achievable).

Goal planning is extremely important and essential part of planning, because it enables adjustment of different decision making carriers of different levels. Goal system is based on variety of quantitative and qualitative goal concepts as outlines of desired company development. It is considered that every company should aspire towards two operative goals: achieving enough incomes (economical component), accomplishing and maintaining financial balance (financial component) because long term non-realisation of those goals endangers company existence.

Figure 1. Plait of goals organization (OSMANAGIĆ – BEDENIK, 2002)

In substantial sense planning process includes these phases and stages:

goal analysis (defining goals and their content, relations between goals, forming and forming goals) problem analysis (problem cognition, its structuration and forming) possibility analysis (searching for possibilities and their forming) prognosis (what will happen) evaluation (connecting values to alternatives) decision (choosing one possibility)


122

realisation control (comparison of achieved and planned).

Planning instruments are techniques and methods which serve to planner as a support in

planning process. One of the simplest systematisations starts with dividing instruments on qualitative and quantitative. Qualitative planning techniques are based on knowledge, experience, understanding, thinking and intuition, and are especially applied in analysis phases, searching for alternatives, their evaluation and decision making phase. Quantitative planning techniques are based on mathematically-statistical actions and stretch from simple time analysis chains to mathematically demanding procedures of optimisation.

Table 1. Quantitative and qualitative techniques of planning (OSMANAGIĆ, 2002)

Planning techniques

qualitative methods

Decision Tree Decision Table Delphi method Scenario techniques Creative techniques:

- Brainstorming - Method 635 - Sinectic - Morphological analysis

quantitative methods

Time Series Analysis Exponential smoothing:

Trend Extrapolation - Moving Average Method

Regression Analysis Methods of Mathematical Programming

- Linear Programming - Nonlinear Programming - Dynamic Programming - Parametric and Stochastic Programming - Heuristic Programming - Simulation

Special Optimization Procedures Network Planning Technique Benefit Analysis

Decision tree is applied when complex and insecure decision situations condition

multiple solutions. Different solution paths together with their consequences are shown as tree branches. Decision point serves as starting point; alternative solutions are shown as decision branches.

Preparation of planning includes information acquisition, plan guideline elaboration and plan guideline documenting.

Planners are over flown with information, of which many are not usable. There is a problem with finding relevant information for planning in such enormous quantity of information. Knowing different types of information and distinguishing criteria is very useful. There are original (primary) and derived (calibrated) information. Original are acquired by direct information search, and derived are result of transmission, translation or reconstruction of individual information. Information sources are very important, therefore internal and external information sources are distinguished.


123

During determination of current information state, control question lists are helpful: Which external information is acquired regularly and which occasionally? Which internal information is acquired regularly and which occasionally? Is the information complete? What does their possible incompleteness refer to? Does available information fulfil their purpose? Is the information already relevant for decisions? Is the information reliable and correct? Is the information precise? Can the information be evaluated? Is the information compatible with information needs of other fields? In relations of offer, request and need there is an overlap; the bigger the common field,

the better role fulfilment information system has, as well as reporting system, which is its important part.

Legend: 1- information offered, but not requested, 2 - information requested, but not offered, 3 - information necessary and requested, but not offered, 4 - information offered and requested, but not necessary, 5 - information offered, but neither necessary not requested, 6 - information requested, but neither offered not necessary, 7 - information requested, but not necessary and needed

Figure 2. Relationship between supply, demand and need for information (BOLFEK, 2004) 2.2. Operation planning

Operation planning is short term planning for period up to one year, and it meets market and tax-legal accounting period. It is derived from strategic planning and it contributes to achieving planned strategy, it is more detailed and specific. Operation planning is conducted permanently and minimally on the level of business fields: sales, production, acquisition, finances and employees. Its task is sententious analysis with purpose of optimal usage of given potential effects with given products on current market.

Operation planning is tightly connected with term of budgeting, accounting. Usually, budget or account is monetary plan (especially cost) which, according to responsibility fields, shows (costs) values for certain planned period (a year or less), obligatory for relative responsibility carriers.

In company practice, long term investment budgets and financial budgets are often created.

Operations planning basic activities are: sale planning, production planning, acquisition planning, financial planning and employees planning.

Marketing plan, together with conduction and control of marketing activities, is important part of marketing strategy, which is part of company's business strategy.

Marketing planning is wider term which includes: plan for sales, traffic, measures and cost.

Acquisition plan is derived from sales, production and stock plan, and directly influences result plan.


124

Acquisition plan can be analytically observed as: planning acquisition program (acquisition and storage goals) and planning acquisition measures.

2.3. Harmony of planning process

Mutual dependence of individual partial plans is particularly stressed, together with their relation towards business plan: substantial, time and hierarchy mutual connection.

Mutual connection consequences are disclosed in fact that activities and measures cannot be determined separately in one part of overall plan; they must be determined in relation to other partial plans. Without mutual coordination, each field aspires to concentrate on its own activities, and by planning process compatibility between different individual priorities and orientations is achieved.

Harmonisation is a wider term which includes coordination as horizontal adjustment on different hierarchy levels.

2.4. Instruments of coordination

Instruments of coordination are auxiliary assets for achieving partial plan compatibility on the same hierarchy levels. There are different coordination instruments classifications: most commonly direct and indirect coordination.

Figure 3. Relationship between supply, demand and need for information (Indirect Instruments of Coordination (OSMANAGIĆ, 1998)

Direct coordination is applied in small companies, where all partial plans are united and

coordinated through whole overall plan. Coordination task takes central planning place. By company size growth internal complexity and dynamics increase, so that indirect

coordination instruments are used.

2.5. Problems of planning in practice

Since complexity reduction, by information gathering, is one of basic planning tasks, organisation culture can support as well as obstruct planning process.

Focusing on central values – organisation vision is increased by preparedness of conducting strategies, goals and measures in daily work.


125

Implementation and application of planning in business practice is followed by problems and limitations. Organisationally conditioned limits and behaviour conditioned limits are among the most important ones.

Organisationally conditioned limits can be separated into those construction conditioned and process conditioned.

Construction conditioned limits relate to problem defining of planning task carriers. Although the advantage goes to headquarters task planning organisation, due to hierarchy status knowledge concentration, deficiencies are seen in predominant focus of linear managers on daily work and neglecting coordination with strategic controlling dimension.

How important and common planning problems in practice are, says their list: planning and routine of daily work, linear manager dislike of planning, insecurity, optimistic planning mentality, silent reserves, improper plans, plan violation, plan revision, information concealment and manipulation, task carrier’s bureaucratic behaviour, neglecting strategic aspects, neglecting whole organisation interest and department egoism and self-obligation escalation.

Planning preparation varies from company to company, where mutual understanding is stressed, not theoretical tasks no one understands.

Described repulses and planning problems exist in many companies and they should be reckoned. The problems are decreased by cooperation and communication with individual fields, not by authority usage. 3. CONCLUSION

Under the influence of external and internal conditions in a company, and influence of

growing competition, continuous management development is necessary, as well as whole company’s structure development. It is important to follow environment dictated standards and plan further development based on gathered information. Planning preparation varies from company to company, where mutual understanding is stressed, not theoretical tasks no one understands. Described repulses and planning problems exist in many companies and they should be reckoned. The problems are decreased by cooperation and communication with individual fields, not by authority usage. It is necessary to constantly have in mind that planning processes are often inefficient due to inaccurate attitude towards planning. Plans themselves do not determine company’s destiny; manager’s experience and intuition are also necessary. Doubt and repulse towards planning do not necessarily mean bad intentions and adjustment; they can be consequence of improper attitude and relation between planer and controller. 4. REFERENCES AVELIN-HOLJEVAC, I. (2004): Planning and Controlling. RRIF, 8 (10): pp. 66-69. BOLFEK, B. (2004): Requests information system of controlling. RRIF, 8 (3): pp. 56-62. FIGURIĆ, M. (2003): Menadžment troškova u drvnotehnološim procesima. Sveučilišni udžbenik,

Sveučilište u Zagrebu, Šumarski fakultet, pp. 1-249. GRLADINOVIĆ, T. (1999): Upravljanje proizvodnim sustavima u preradi drva i proizvodnji namještaja,

Sveučilišni udžbenik, Sveučilište u Zagrebu, Šumarski fakultet, pp. 1-296. MAJDANDŽIĆ, N. (1994): Kompjuterizacija poduzeća. Strojarski fakultet u Slavonskom Brodu,

Slavonski Brod. OSMANAGIĆ, B.N., (1998): Kontroling: abeceda poslovnog uspjeha. Školska knjiga, Zagreb. OSMANAGIĆ, B. N., 2002: Operativno planiranje. Školska knjiga, Zagreb. SUJOVÁ, A., 2004: SWOT analysis – information support for building development strategy of the

Slovakian wood industry. Drvna industrija 56 (4): pp. 199-207.


127

Effect of Cell-Wall Angle on the Uniaxial Crushing Behaviour of Paper Hexagonal Honeycombs

SMARDZEWSKI Jerzya*– MAJEWSKI Adama – PREKRAT Silvanab

a Poznan University of Life Sciences, Poznan, Poland b University of Zagreb, Zagreb, Croatia


Abstract – The following factors: paper mass, apparent density as well as cell shape and dimensions exert a significant impact on the stiffness and strength of cell panels. In the available literature on the subject, there are no papers reporting research results on the stability of paper honeycombs depending on the cell-wall inclination angle and apparent density of a honeycomb. The objective of this research project was to determine the influence of the cell-wall angle of irregular hexagonal cells as well as their apparent density on the stability of a paper honeycomb. The investigations were realised by carrying out experimental tests and then comparing the obtained results with the results of numerical calculations. Empirical tests were conducted using cores made from paper honeycombs of hexagonal cells differing with respect to wall inclination angles which ranged from 55° through 66° to 82°. It was demonstrated that together with the increase of the cell-wall gradient above 55°, the value of the honeycomb critical force as well as its apparent density also increased. For the angle of 82°, despite high apparent density, cell slenderness increased and its stability decreased. In addition, numerical models were elaborated sufficiently correctly ensuring convergence of the calculations with the results of experimental measurements.

paper honeycomb / cell-wall angle / crushing / numerical analysis / experiment 1. INTRODUCTION

Layered structures with a cell core are widely used as secondary systems in aeronautics and car industry as, for example, bonnets or doors. Modelling of small velocities, low impact energies leading to decreases of construction strength by 50 % remain among the main challenges for designers. Because this kind of action is characterised by the same result as the quasi-static loading, scientific investigations focus on studies of the core behaviour – i.e. of the honeycomb during compression. The phenomenon of crushing has been well recognised over the years but its mechanism has not been comprehensively described and the proposed model cannot fulfil industrial requirements (GUPTA – ABBAS 2000; SINGACE, 1999; WIERZBICKI, 1983). More comprehensive studies on mechanical properties of cell panels embraced structures manufactured from metal. These studies described strength properties of aluminium sandwich type panels in the following tests: bending, compression and stability (JEN et al., 2008; KHAN, 2006; PAIK et al., 1999; SAID et al., 2009). Orthotropic properties of an aluminium core in the form of a honeycomb were determined (SCHWINGSHACKL et al., 2006). A novel approach to the analytical description of the core structure was presented and a new solution consisting in combining core elastic properties with the geometry and mechanical properties of the material from which the core was manufactured was proposed (MERAGHNI et al., 1999).

Usually, cell structures are employed as stratified systems with metal facings. In their investigations, TAN et al. (2007) ascertained the effect of different assumptions, materials, facings as well as loading on the absorption energy and deformations of the applied cell structures. In those investigations, the above researchers employed three-dimensional models of finite elements corresponding to the mechanics of the following orthotropic bodies: composite fabrics, wood, glass, aluminium alloys 2024-T3 as well as fibrous anisotropic composites T-300. The obtained results indicate that the deformation and energy dispersion of


128

the surface deformation of the examined structure depended, in a significant way, on the number of layers, material used as facing, load thickness and area. PETRAS – SUTCLIE (1999) analysed models of damages of laminated stratified aluminium beams with a Nomex core in the form of a honeycomb. These researchers presented theoretical models which utilised the mechanics of a honeycomb and the classical beam theory. They demonstrated that in the course of a three-point bending, there was a correlation between the type of damage and construction bearing capacity and laminate thickness and the length of the honeycomb. In addition, the results of theoretical calculations were corroborated by experimental measurements. ZHOU et al. (2012) determined plastic behaviour of a Nomex honeycomb in the course of shearing combined with compression. Moreover, the influence of the sample inclination angle on plastic behaviour during a complex loading state was assessed. Two different cases of sample damage were registered: plastic buckling and fracture of cell walls. The elaborated research results provide an excellent contribution to the elaboration of constitutive models of Nomex cell panels in complex loading state.

Hexagonal honeycomb cells in a transverse plane provide exceptional cushioning material. Their constructional parameters and impact velocities exert a significant influence on the consequences of the action. In experiments conducted by DEQIANG – WEIHONG (2009), using the finite element method, they investigated correlations between construction parameters of the honeycomb and strain after the loss of stability at the impact velocities ranging from 3 to 250 m/s. They demonstrated that for constant honeycomb parameters, strains were proportional to the square of the impact velocity. Moreover, HU et al. (2013) studied the effect of the cell-wall inclination angle on the dynamic crushing of the honeycomb in transverse plane. They demonstrated that the size of crushing depended on the apparent density of the honeycomb and the inclination angle of cell walls. The highest strength was observed in cells with wall inclination angle equalling 45o. It should be added that significant orthotropic properties of the core become apparent when the inclination angle exceeds 30o.

Few papers deal with modelling of mechanical properties of cell panels with a paper honeycomb (SEIDL, 1956). SAM-BREW et al., (2011) carried out investigations on the effect of the type of paper, cell orientation, their height and arrangement on stiffness and strength of cell panels. WANG – WANG (2008) as well as PING – WANG (2010) determined the effect of density and moisture content of cell panels on paper core stability. Furthermore, a mathematical model was developed of the dependence between absorption energy of cell panels and their moisture content (WANG – PING 2010). The impact of the auxetic core structure of the cell panel and the kind of the facing material on cell panel stiffness was discussed in a paper by SMARDZEWSKI (2013). SMARDZEWSKI – PREKRAT (2012) demonstrated that cores of cell panels manufactured from HDF facings and irregular hexagonal honeycomb cells level out well strain differences between panel layers. In addition, paper mass, apparent density and shape and dimensions of cells exert a significant influence on cell panel stiffness and strength. It was found that during the process of bending of cell panels with a paper core, multiple buckling of cell walls takes place (SAM-BREW et al., 2011). However, no articles can be found discussing research results of paper honeycomb stability depending on the inclination angle of cell walls and apparent density of the honeycomb.

The objective of this research project was to determine the effect of the inclination angle of irregular hexagonal cells and their relative density on the stability of a paper honeycomb. Experiments were realised by carrying out experimental tests and comparing the obtained results with numerical calculations. 2. MATERIAL AND METHODS

Paper honeycomb cores with hexagonal cells of hc – 10 mm height, paper thickness of t = 0.2 mm and 140 g/m2 density were prepared for empirical investigations (Figure 1). Paper


129

honeycomb in pressed form (for stretching) was obtained from the Company Axxion Industries Poland Ltd. Cells were stretched in such a way as to obtain three structures differing with regard to the size of the cell and cell-wall angle inclination (Figure 2). A-type cells were characterised by maximal stretching ∆L. The extension of B and C cells amounted to 0.5 ∆L and 0.25 ∆L, respectively. The obtained honeycombs were used to obtain ten samples each with dimensions 10 mm x 50 mm x 50 mm (Figure 2). The surface of samples was scanned and then extended in the CAD system to the height of 10 mm (Figure 3). Dimensions of hexagonal samples are illustrated in Figure 4. As evident from this Figure, the obtained cells differed with respect to their length and angle of wall inclination. Walls of the A-type cells were inclined at the angle of φ≈55°, while those of B and C cells, at angles of φ≈66° and φ≈82°, respectively.

In all, 30 samples were prepared and were subjected to uniaxial compression using for this purpose a Zwick 1445 test machine applying loading velocity of 10 mm/min. The applied force was measured with the accuracy of 0.01 N and deflection with up to 0.01 mm accuracy.

Figure 1. Model of a hexagonal core cell

Figure 2. Samples of hexagonal cells employed in experiments: A – φ=55°, B – φ=66°, C – φ=82°


130

Figure 3. Model of cells created in CAD on the basis of scanned image

Figure 4. Cell dimensions depending on the wall inclination angle:

A – φ=55°, B – φ=66°, C – φ=82° It was further decided to determine the influence of the honeycomb apparent density on

the value of the critical force causing cell-wall buckling. Relative density of the paper honeycomb depends on its structure, i.e.: the thickness, length and inclination angle of cell walls. This is expressed by the following quotient:

(1)

where: pc – density of the paper honeycomb, pp – density of the paper forming the honeycomb.

Assuming further that b = c = d = 1 and assuming that

(2)

and,

(3)

where: mp – mass of the paper forming the honeycomb, Vc and Vp – respectively, volume of the paper core and volume of paper, pc and pp density amounts to:

(4)

!" !# !# !# $ (5)

hence,

!" !# !# !# $

(6)


131

3. NUMERICAL ANALYSIS

Three solid models of single cells were prepared for numerical calculations (Figure 5). The models consisted of a paper core of hexagonal cells to which elastic properties of paper Ep = 2000 MPa were assigned (SZEWCZYK, 2010; UESAKA et al., 1979).

Figure 5. Solid models used for numerical calculations:

A – φ=55°, B – φ=66°, C – φ=82° Next, appropriate numerical models were designed employing for this purpose 20-node,

brick-type finite elements in the environment of the Autodesk Simulation Multiphysics® 2013 software. The models were then supported in such a way as to bring about cell wall buckling under the influence of uniaxial compression. First, the value of the critical force causing loss of stability of each of the examined models (A, B and C) was calculated. Next, calculations of the post buckling behaviour of the examined systems were performed for loads determined in this manner.

4. RESULTS AND DISCUSSION

Figure 6 presents an example picture of a honeycomb subjected to uniaxial compression. It illustrates the form of buckled cells following their loss of stability. It is evident from this Figure that top edges of cell walls as well as surfaces of side walls underwent destruction. Figure 7 illustrates the dependence of force on displacement. It can be noticed on the basis of this Figure that the value of the critical force PCR depended quite clearly on the inclination angle of the honeycomb cell walls. The highest PCR value was observed in the case of cells with the cell wall inclination angle of φ=55°. The lowest critical force occurred during compression of the honeycomb whose cell walls were inclined at the angle of φ=82°. In addition, once the critical load was exceeded, even slight increases or decreases of force were accompanied by large displacements confirming loss of stability of cell side walls. Similar runs were reported by other researchers investigating the stability of aluminium, plastic or paper honeycombs (DEQIANG – WEIHONG, 2009; HU et al., 2013; MERAGHNI et al., 1999; PAIK et al., 1999; PETRAS – SUTCLIFFE, 1999; PING – WANG, 2010; SAID – TAN, 2009; SCHWINGSHACKL et al., 2006; SEIDL, 1956; SINGACE, 1999; WANG – PING, 2010; WANG –

WANG, 2008; WIERZBICKI, 1983; ZHOU et al., 2012).


132

Figure 6. Deformation of cells measuring 10 mm x 50 mm x 50 mm

following a uniaxial compression test

Figure 7. Stiffness of cells measuring 10 mm x 50 mm x 50 mm

during uniaxial compression: A – φ=55°, B – φ=66°, C – φ=82°

Figure 8. Area of pressure and critical force for cell wall samples measuring

10 mm x 50 mm x 50 mm: A – φ=55°, B – φ=66°, C – φ=82°

As demonstrated on samples measuring 10 mm x 50 mm x 50 mm, the value of the critical force depended on the inclination angle of side cell walls. Moreover, this angle was also found to affect changes in the pressure area as well as cell relative density (Equation 6). Figure 8 presents correlations between the pressure area and value of the critical force. It is


133

evident that together with the growing pressure area, the value of the critical force also increased reaching the following values: 1299 N, 1587 N and 2002 N for A, B and C samples, respectively. Simultaneously, the area of pressure increased from 210.1 mm2 to 282.7 mm2 and 773.6 mm2. In the case of A and B models, the pressure area increment of 34.5 % resulted in the increase of the critical force value by 22.1 %. The above-mentioned differences for B and C models amounted to 73.6 % and 26.1 %, respectively. Therefore, it can be concluded that pressure area increments were not accompanied by proportional increases of the critical force. This may be attributed to the fact that honeycomb is not made up of ideally hexagonal cells. It can be observed from Figure 1 that cells are characterised by different lengths of walls. Therefore, their stabilities vary and affect non-linear value changes of the critical load. Figure 9 illustrates the way of deformation of individual cell walls. The left column of images illustrates the form of buckling under the influence of the critical load, while the right column shows the form of deformation after the loss of cell wall stability. It is evident from this Figure that the critical load caused, primarily, deformations of top edges of cell walls as well as buckling of side walls. Because of their different lengths, it is the longest walls that undergo buckling first. Places where the cells join, forming perpendicular ribs undergo only compression. Once the critical loading is exceeded, edges and walls of cells undergo further deformations. Vertical ribs also undergo buckling. In addition, it can be observed that the inclination angle of cell walls exerts a significant influence on the status of cell deformations of the honeycomb. Greater wall inclination angles make cells slender and sensitive to buckling. Figure 10 illustrates values of critical forces calculated numerically for a single cell. These values were collated with the results of laboratory measurements together with values of pressure areas and cell relative density. The smallest critical load of one cell was found to occur in the case of model C. It is a slender cell of small pressure area (9.33 mm2) and of high relative density (1.01). In the case of this cell, the loss of stability occurs as a result of a one-sided buckling of all cell walls. Despite the fact that the cell is characterised by high relative density, nevertheless it exerts impact on the increase of stability of a system made up of many cells. In this case, stability is affected by a small pressure area and slenderness of the cell. Comparing the results of numerical calculations determined for this cell with empirical values, it should be stressed that the numerically determined value of the critical force of 30.68 N exceeded by 26.9 % the value of 24.15 N established in the laboratory. Cell B is characterised by the pressure area of 9.50 mm2 and relative density of 0.51. In this case, the experimentally determined critical force causing loss of cell wall stability amounts to 53.33 N. However, numerical calculations deliver a higher value which amounts to 81.08 N and exceeds by 52 % laboratory values obtained empirically. The largest pressure areas were determined in A cells and their apparent density amounted to 0.43. Numerically calculated value of the critical force of 66.5 N exceeds the value determined experimentally of 59.74 N by 11.3 %. On the basis of the above-performed comparisons as well as comparisons with the results of measurements of the stability of a honeycomb made up of many cells, a regularity emerges indicating that critical loads of a honeycomb and a single cell depend on the inclination angle of cells. Together with the increase of this angle to above 55°, the stability of the structure increases. In the case of honeycomb, the critical force increases together with the increase of relative density. A similar correlation can be observed in the case of single cells A and B. The C cell, due to its considerable slenderness easily loses its stability despite high relative density.


134

Figure 9. Wall buckling of single cells for critical and after-critical loads:

A – φ=55°, B – φ=66°, C – φ=82°

Figure 10. Relative density and critical force for single cells:

A – φ=55°, B – φ=66°, C – φ=82°


135

5. CONCLUSIONS

On the basis of the analysis of the obtained research results, the following conclusions can be put forward: − together with the increase of the inclination angle of cell walls above 55°, the value of the

critical force of the honeycomb as well as its relative density increased, − the stability of a single cell depended on the inclination angle of walls and increased

together with its growth, − for the 82° angle, despite high relative density, cell slenderness increases and its stability

declines, − numerical models were designed sufficiently correctly which assured convergence of

calculations with the results of empirical measurements. 6. REFERENCES DEQIANG, S.; WEIHONG, Z. (2009): Mean in-plane plateau stresses of hexagonal honeycomb cores

under impact loadings. Composite Structures 91: pp. 168–185. GUPTA, N.K.; ABBAS, H. (2000): Mathematical modelling of axial crushing of cylindrical tubes.

Thin-walled Structures 38: pp. 355-375. HU, L.; YOU, F.; YU, T. (2013): Effect of cell-wall angle on the in-plane crushing behaviour of

hexagonal honeycombs. Materials and Design 46: pp. 511–523. JEN, Y.M.; CHANG, L.Y. (2008): Evaluating bending fatigue strength of aluminium honeycomb

sandwich beams using local parameters. International Journal of Fatigue 30: pp. 1103–1114. KHAN, M.K. (2006): Compressive and lamination strength of honeycomb sandwich panels with strain

energy calculation from ASTM standards. Journal of Aerospace Engineering 220: pp. 375-386. MERAGHNI, F.; DESRUMAUX, F.; BENZEGGAGH, M.L. (1999): Mechanical behaviour of cellular

core for structural sandwich panels. Composites Part A 30: pp. 767–779. PAIK , J.K., THAYAMBALLI , A.K., K IM , G.S. (1999): The strength characteristics of aluminum

honeycomb sandwich panels. Thin-Walled Structures 35: 205–231. PETRAS, A.; SUTCLIFFE, M.P.F. (1999): Failure mode maps for honeycomb sandwich panels.

Composite Structures 44: pp. 237-252. PING, Y.; WANG, Z.W. (2010): Plateau Stress of Paper Honeycomb as Response to Various Relative

Humidities. Packag. Technol. Sci. 23: pp. 203–216. SAID , M.R.; TAN, C.F. (2009): Aluminium honeycomb under quasi-static compressive loading: an

experimental investigation. Suranaree Journal of Science and Technology 16: pp. 1-8. SAM -BREW, S.; SEMPLE, K.; SMITH , G. (2011): Preliminary experiments on the manufacture of

hollow core composite panels. Forest Products Journal 61: pp. 381-389. SCHWINGSHACKL, C.W.; AGLIETTI, G.S.; CUNNINGHAM , R.R. (2006): Determination of honeycomb

material properties: Existing theories and an alternative dynamic approach. Journal of Aerospace Engineering 19: pp. 177-183.

SEIDL, R.J. (1956): Paper-honeycomb cores for structural sandwich panels. In: Forest Products Laboratory. Forest Service U. S. Department of Agriculture. Madison 5, Wisconsin.

SINGACE, A.A. (1999): Axial Crushing analysis of tubes deforming in the multilobe mode. International Journal of Mechanical Sciences 41: pp. 865-890.

SMARDZEWSKI, J.; PREKRAT, S. (2012): Modelling of thin paper honeycomb panels for furniture. In: Proceedings of the International Conference Ambienta “Wood is Good – With Knowledge and Technology to a Competitive Forestry and Wood Technology Sector”. Croatia. October, 2012. pp. 179-186.

SMARDZEWSKI, J. (2013): Elastic properties of cellular wood panels with hexagonal and auxetic cores. Holzforschung 67 (1): pp. 87–92.

SZEWCZYK, W. (2010): Packaging Paper – Orthotropic Elastic Material. Przegląd papierniczy 66: pp. 205-209.

TAN, X.; CHEN, X.; CONWAY, P.P.; YAN, X.T. (2007): Effects of plies assembling on textile composite cellular structures. Materials and Design 28: pp. 857–870.


136

UESAKA, T.; MURAKAMI , K.; IMAMURA , R. (1979): Biaxial tensile behaviour of paper. Tappi Journal 62: pp. 111-114.

WANG, Z.W.; PING, Y. (2010): Mathematical modelling of energy absorption property for paper honeycomb in various ambient humidities. Materials and Design 31: pp. 4321–4328.

WANG, D.M.; WANG, Z.W. (2008): Experimental investigation into the cushioning properties of honeycomb paperboard. Packag. Technol. Sci. 21: pp. 309-316.

WIERZBICKI, T, (1983): Crushing Analysis of Metal Honeycomb. International Journal of Impact Engineering 1(2): pp. 157-174.

ZHOU, Z.; WANG, Z.; ZHAO, L.; SHU, X. (2012): Experimental investigation on the yield behavior of Nomex honeycombs under combined shear-compression. Latin American Journal of Solids and Structures 9: pp. 515 – 530.


137

Impact of the Economic Crisis on the Wood Industry Production in Republic of Macedonia

STANKEVIK SHUMANSKA Miraa*– MELOSKA Živkaa – EFREMOVSKA Violetaa

a Faculty of Design and Technology of Furniture and Interior - Skopje, University Ss Cyril and Methodius - Skopje, Republic of Macedonia


Abstract - Wood industry production in the Republic of Macedonia, or wood processing and furniture manufacturing in recent years, is facing a series of challenges and problems of a structural nature, which, if not resolved promptly have a relatively high potential to threaten its competitiveness. Moreover, recently, before this important traditional industry haltingly new problem - the economic crisis, which hides the real danger further worsen its position in the industrial structure of the domestic economy. The purpose of this paper is to analyze and identify the impact of the economic crisis on the performance of wood industry sector. Consequences of this crisis are felt in terms of the volume of industrial production especially in wood processing and the level of export activity, which have negative trends or intense rate decline in the analyzed period (2006-2012 year). The level of employment in wood processing and furniture production has increased in intensity studied period.

economic crisis / wood processing / furniture production / industrial production / employees / export 1. INTRODUCTION

The global economic and financial crisis or recession, are strong economic characteristic which in recent years affect all global economic trends. The recession has already received its name in the global repository of economic science as the recession of late two thousands and its intensity and size influence widely shake the economic foundations of the modern world. There were many pessimistic thoughts to one side, but also predictions still have something easier scenario out of the crisis faster economic recovery, on the other hand.

Regardless of which of these two considerations would undoubtedly lean we can say that the impact of the crisis and the recession comes in a big way in the Republic of Macedonia in its economic trends, and the broader social context. The impact of the economic crisis is evident and the wood processing and furniture production, i.e. wood industry production in the Republic of Macedonia. Given the impact of the crisis in a broader context, it is necessary to determine the dynamics and intensity of the impacts of the crisis. To combat the crisis is not enough to note that the present crisis periods and operating results are not good. Quality fight the economic crisis in order to achieve a high degree of management crisis and out of crisis, it is necessary to determine the impact of the crisis with all the repercussions of dynamic performance and to design solutions proposed to minimize or overcome specific crisis. The purpose is focused this paper, i.e. to analyze and identify the impact of the economic crisis on the performance of activities of wood processing and furniture production in the Republic of Macedonia. 2. FEATURES OF THE WOOD INDUSTRY IN THE REPUBLIC OF MACEDONIA AND ITS PERFORMANCE

The wood industry is one of the traditional industries in the Republic of Macedonia. The

wood industry production consists mainly of the processing of wood and wood products and


138

furniture manufacturing. But the entire process of production, analyzed by stages of production mainly includes the following stages: wood processing, production of wood products, furniture manufacturing and service performance on wood industry production.

Wood industry sector in the country stands out according to their characteristics. As one of the recognizable those distinguished it from other industries and are considered as advantages are as follows:

• Tradition of working with the existing infrastructure and production facilities, and available workforce supported by attractive young people, • Permanent export orientation of production, • Relatively low value of investments in production facilities and per employee, • Existence of the wood industry cluster, and • Relatively ecologically acceptable industry.

As a consequence of the real economic situation in which the state, the wood industry is faced with a number of limitations and weaknesses related to:

• Insufficient size and structure of exports and imports, which are due to the loss of important markets and unorganized approach to foreign markets, emphasized the import of wood products industry from EU countries and beyond, as well as the inability to finance exports and investments (insufficient) own accumulations, • Low utilization of production capacity, • need for technological modernization (computerization and automation of production) • Low certification and poor quality control, • Lack of a recognizable brand of Macedonian wood industry, • compete price which is the biggest obstacle to Macedonia's exports of wood products and furniture, where the competent authorities are expected introduction of incentive (incentive) measures to reduce the cost of production, • Low energy efficiency of technological processes and negligent use of wood waste as biomass for the production of renewable energy. Participation that wood industry has in the total number of employed persons in the

Republic of Macedonia, as well as in total exports and in creation of total GDP is shown in Table 1. Table 1. Participation of the wood industry of the Republic of Macedonia in the total GDP (value

added), exports and employment (in %)

Participation of wood industry in percent in

2006 2007 2008 2009 2010 2011

total GDP (value added) 0,6 0,5 0,6 0,6 0,4 0,4total exports 0,8 1,0 1,1 1,3 1,0 0,9total employees 1,7 1,6 1,6 1,6 1,5 1,3 Source: State Statistical Office of Macedonia, Publications

The share of this industry in the structure of total value added and total GDP shows a

trend of slight movements in variables dynamics. On average 0.6 % in 2006 falling to 0.5 % in 2007, and in 2010 reached the level of around 0.4 %. This level is maintained in 2011. As its share in total exports and here we have a trend variable movements slightly more pronounced dynamics where the period 2007 - 2009 increased from 1.0 % to 1.3 %, and in 2010 dropped again to 1.0 %. The continuity of decline continues in 2011 to 0.9 %.

The biggest share of the wood industry represents its participation in total employment in the Republic of Macedonia. From Table 1 it is seen that its impact on overall employment declines continuously from 1.7 % in 2006 to 1.3 % in 2011.

Previous data show that the performance of this traditional industry, although still less significant impact on the industry and economy of the Republic of Macedonia. Therefore


139

there is a real need for taking measures for easier overcoming the negative effects produced by the economic crisis, thereby preserving its competitiveness in the market.

Presented specifics point to the fact that the wood industry of the Republic of Macedonia is a very fragile industry of which lie ahead and some restructuring. The latest economic crisis which unexpectedly long exists now a threat to wood industry sector in the country.

In order to realize the economic consequences of recession, will make a brief review of its impact on wood industry production, the export sector and the number of employees in this sector. The relevant period of time is 2007 - 2012 year. Exactly in this period of economic crisis intensity is present, so that the economic performance of the wood industry is exposed to the direct impact of adverse changes from the crisis. 3. IMPACT OF ECONOMIC CRISIS ON WOOD INDUSTRY PRODUCTION

The situation in the industrial production of wood industry will show through the base index of industrial production as the average of the base 2005 according to data from the State Statistical Office of the Republic of Macedonia. Base index of industrial production measures the change in industrial production compared with a basic period (in this case 2005) to reflect a kind of its normal position.

Base index of industrial production (2005 = 100) in the manufacturing industry, wood processing and furniture production are shown in Table 2. Table 2. Index of industrial and wood industry production

YearManufactiring

industryWood procesing

Furniturepoduction

2007 112,2 93,4 83,82008 118,8 71,4 223,42009 106,5 41,8 159,92010 98,5 61,7 128,62011 103,9 48,5 159,52012 97,3 52,3 136,3

Base index of industrial production (2005 = 100)

Source: State Statistical Office of Macedonia, Publication - Industry, 2007-2012

The movement of the base index of production in the manufacturing industry indicates

that in the first half of the period 2007-2010 compared with the average since 2005 has seen a slight decline of 98.5 %, and in 2011 a small increase of 103.9 % and in 2012 again fall to 97.3 %. This means that the recession back industrial production level of 2005, although marked by a continuous upward trend.

In terms of total industrial production base movement index wood industry production especially in the wood processing indicates that this branch as a whole is facing a crisis. The dynamics is the drastic change in terms of what should be a normal condition in the base 2005 (reducing production of 48.5 % in 2011 and 52.3 % in 2012).

Unlike the movement of the base index for processing wood, the same at production of furniture has a variable dynamic. Except in 2007 where the base index is below the level of 2005 (83.8 %), the base index of industrial production of furniture increased. The largest increase recorded in 2008 (223.4 %) to the 2012 decline of 136.3 % compared to the average of 2005. The level of wood industry production in analyzed period (2007-2012), especially in wood processing is not the level that is recognized in respect of representative 2005. Production of furniture is characterized by dynamic growth in the studied period.


140

4. THE IMPACT OF ECONOMIC CRISIS ON THE NUMBER OF EMPLOYEES IN THE WOOD INDUSTRY

Wood industry participates with average from 1.5 % in the total number of employed

persons of the Republic of Macedonia in the period 2006 - 2011. The influence of the number of employees in this sector is analyzed through basic index of annual change of staff in the sector and the manufacturing industry. The base year is 2005, when the great door begins to announce economic crisis in 2007 has had its beginning. Data were obtained by the State Office of Statistics and shown in Table 3. Table 3. Index of employed in manufacturing and wood industry

YearManufactiring

industryWood procesing

Furniturepoduction

2007 96,2 88,5 94,72008 96,0 93,0 105,52009 89,5 86,5 103,12010 89,3 114,0 118,72011 90,3 112,5 122,42012 87,4 111,7 118,9

Indices of employees(2005 = 100)

Source: State Statistical Office of Macedonia, Publication - Industry, 2007-2012

Movement of the basic index of employees in the average of 2005 shows an increase in wood processing and furniture manufacturing, as opposed to total employment in an industry where there is a tendency of falling within the observed period (Table 3). It is slightly more pronounced increase in staff in the production of furniture in the period 2007 - 2012 has seen a growth index of employees by 22.0 % compared to 2005. In contrast, the processing of wood is less noticeable intensity increase employment by about 14.0 % compared to 2005. Base year index employed in the manufacturing industry decreased by nearly 13.0 % in the analyzed period.

From the foregoing it can be seen that the economic crisis has reduced the number of employees in the total industry and this negative impact is still present and further deepens. This is not the case with the wood industry sector where is present trend of increasing employment and in wood processing and the production of furniture. 5. ECONOMIC CRISIS AND EXPORT FROM THE WOOD INDUSTRY

The economic crisis whose effects are felt in the domestic economy is basically caused by reduced aggregate demand for goods and services in the world, especially in developed countries. Given the link between domestic wood industry to foreign markets, in terms of raw materials, intermediate goods and finished products, there is a real risk of deterioration in exports from this sector. Analysis of export of wood industry was based on the available data are given in Table 4. Data were obtained from the State Statistical Office of the Republic of Macedonia and analyzed for the period 2006 - 2011 year.

From the data in Table 4 can be seen that the impact of the economic crisis on exports of wood industry has variable dynamics in the analyzed period. According to the annual index change can be said to be of positive 73.2 % growth in exports in 2007 compared to 2006, in 2008 it exported about 22.7 % compared to 2007, which means that the trend increased export declines. The index of annual change in 2009 shows no decline in exports even - 21.5 %


141

compared to 2008 when it realized the biggest export of wood industry in the analyzed period. In the period 2010 - 2011 year, we have increased the index of annual change in the relationship of 2009 and 2010 from 1.4 % to 10.1 % while it can be said that has not yet reached the level of exports of wood industry since 2008. Table 4. Movement of total exports and exports from the wood industry (in 000 U.S. $)

Year Total exportExports of wood products, wood and furniture

Participation of exports of wood products, wood

and furnitrure in total export (%)

Annual index change of

total exports (%)

Index yearchange in exports of

wood products,wood and furniture (%)

2006 2415161 20368 0,82007 3398268 35268 1,0 40,7 73,22008 3990642 43257 1,1 17,4 22,72009 2708488 33947 1,3 -32,1 -21,52010 3351429 34417 1,0 23,7 1,42011 4455375 37902 0,9 32,9 10,1

Source: State Statistical Office of Macedonia - Publications - Department exchange between Macedonia and abroad, 2006 - 2011, own calculations

If you compare the situation of total exports and exports of wood industry visible is the

fact that the level of reaction to the economic downturn is more pronounced than in the total exports in wood industry sector. The index of annual change in total exports from positive 40.7 % in 2007 compared to 2006, already in 2008 compared to 2007 manifest decline of 17.4 %, and in 2009 compared to 2008 show a downward trend from even - 32.1 %. In the next period, total exports tends to growth, so in 2011 when exports has most of the analyzed period, the annual change in the index increases to 32.9 % compared to 2010. According to previous exports of wood industry manifested stable trends in times of economic crisis in terms of total exports, which is confirmed by dropping its percentage share in the total exports of 1.3 % in 2009 when most of the impact is expressed crisis of just 0.9 % in 2011 when the total export has the largest volume in the analyzed period.

The reasons for this state of Macedonia's exports, and in that context, exports of forest industry is in the nature and character of the economic crisis, the structure of the export structure of wood industry production and high dependence on exports from changes in foreign income, and change in domestic industrial production. The economic crisis is characterized by a decline in aggregate demand across countries in the world resulting in a decline in national production, employment levels and at the national GDP. The export structure and structure of wood industry production complement reasons for this situation. Wood products and furniture fall into the category of consumer goods which in the conditions of crisis have expressed very high degree of elasticity of demand depending on the change in relative income. Unlike the category of so-called subsistence products that have steady demand in terms of the change in income in a recession, most suffer sales of consumer goods which includes wood products and furniture.

6. CONCLUSIONS

The wood industry is a traditional industry in the Republic of Macedonia with its contribution to GDP formation, employment and total exports. It is characterized by a structure in which participation has the processing of wood and wood products and furniture manufacturing. Regarding the extent of finalizing production represented a classic production and manufacturing known as buying supremely product. Wood industry production is characterized by low economic efficiency, high production costs, production of standardized quality and low international competitiveness.


142

The advent of the global economic crisis that overtakes the industry undergoing restructuring had an impact on its performance within the observed period.

The level of wood industry production in the period 2007-2012, especially in wood processing is not on the level that is recognized in respect of representative 2005 when the great door begins to announce economic crisis. Production of furniture is characterized by dynamic growth in the analyzed period.

Economic crisis reduces the number of employees in the total industry and this negative impact is still present and further deepens. This is not the case with the wood industry sector where is present trend of increasing employment and in wood processing and furniture production in the studied period (2007-2012).

Exports of wood industry analysis through annual index changes manifested stable trends in times of economic crisis in terms of total exports for the period 2006 - 2011 year. This is confirmed by dropping its percentage share in the total exports of 1.3 % in 2009, when most evident is the impact of the crisis, only 0.9 % in 2011 when the total export has the largest volume in the analyzed period.

In terms of the process of reorganizing wood industry sector continued impact of the recession can additionally jeopardize the positive performance trend. Therefore, it is taking emergency measures to allow easier overcoming the adverse effects of the crisis, until you perform stabilization of global economic trends. As one of the important measures apart granting soft loans to support the liquidity of companies of the wood industry, delay or exemption of tax obligations, particularly in respect of salaries and benefits, export incentives, measures in the field of social policy to support unemployed and so on. Considering the nature of the crisis, the recovery of the level of aggregate demand and income from abroad will automatically regenerate and condition of the wood industry, traditional industry with its impact on the domestic economy. 7. REFERENCES EFREMOVSKA, V., MELOSKA, Z., SIMAKOSKI , N. (2013): SWOT – Analysis of the wood industry in

Macedonia, International Scientific Conference – Wood Technology and Product Design, Ohrid: (in press).

MELOSKA, Z., PETROVSKA, I. (2012): International Trade in Wood Sawn from Republic of Macedonia, Proceedings, International Scientific Conference – Wood and Furniture Industry in Times of Change – New Trends and Challenges, Trnava: pp. 148 – 154.

MELOSKA, Z., PETROVSKA, I., ANAKIEV , B. (2011): Current Conditions and Strategies for Export Strategies in the Republic of Macedonia, Proceedings, International Scientific Conference – Development Trends in Economics and Menagement in Wood Processing and Furniture Manufacturing, Kozina, Slovenia: pp. 107 – 115.

STANKEVIK SHUMANSKA, M. (2012): Employment in the manufacture of wood and wood products and furniture production in the Republic of Macedonia, Scientific, Professional and Information Journal of Wood Science, Design and Technology - Wood, Design and Technology, Vol. 1, Faculty of Design and Technologies of Furniture and Interior – Skopje: pp. 24-28.

STATE STATISTICAL OFFICE OF REPUBLIC OF MACEDONIA, Publications.


143

Constructions of the Energy-saving Wooden Houses and its Advantages on the Example of Polish Construction

STASIAK-BETLEJEWSKA Renataa*

a Institute of Production Engineering, Faculty of Management, Czestochowa University of Technology, Częstochowa, Poland


Abstract – Contemporary construction, in addition to modern solutions in the field of building architecture, pay particular attention to applied construction materials, which have a great influence on the stability and quality of the building. One of the most well-known materials in the world currently used in residential construction is wood, which is used for the skeletal wooden constructions, as well as energy-saving construction of prefabricated houses. This paper presents today's most popular solutions for wooden construction used in energy-efficient homes in the Polish construction industry, which are also covered by patent protection due to the nature of the solution. The main object of the analysis is both characteristics of wood as a building material, as well as the advantages of timber frame constructions, which also affect the comfort of house users.

wood / construction/ construction materials / wooden frames / wooden prefabricated elements 1. INTRODUCTION

The construction is a field of technical activity which includes: designing and all the techniques and technologies of building home constructions, its maintenance and dismantling. Depending on the materials used in construction there are: wood, brick, stone, concrete and steel. The buildings consist of a plurality of elements, each of which has a particular function and are made of materials with appropriate properties and quality. Construction materials are required above all to be durable (depending on which security of the construction) and hygiene (or lack of harmful effects on health and the environment). Properties of construction materials shall meet the requirements of the relevant standards and technical approvals. The construction works must comply with mostly basic requirements that are designed to eliminate hazards to life, health and property of users and the environment and relate primarily to: the construction safety, the fire safety, the usage safety, adequate conditions of hygiene and health, and environmental protection (in the production of building materials, its use and after the so-called technical life), protection against noise and vibration, energy savings in the building and appropriate thermal insulation baffles. Compliance with these requirements is dependent on, inter alia, the use of carefully selected materials and quality construction.

Building materials used in the construction process are sorted according to various criteria: method of obtaining (natural and industrial), the type of material that are made of, disposition of the material, as well as the criterion of the degree of materials processing or materials applying in the performance of the building individual elements. In the selection of a building material in terms of its quality, physical and chemical properties there are crucial factors such as: density, porosity, humidity, water absorption, moisture absorption, capillarity, permeability, water vapour permeability, infiltration, thermal expansion, thermal conductivity, heat capacity, resistance to freezing, shrinkage, corrosion resistance, fire resistance. The other features of this type include, among others: sound absorption, adhesion or bonding ability. The essential characteristics of construction materials are also mechanical properties such as: durability, elasticity, plasticity, creep, relaxation, ductility, fragility, hardness, abrasion resistance and impact resistance.


144

Wood is a natural construction material (due to the origin and type of material). It is the oldest building material, which is obtained from coniferous trees (pine, spruce, fir) and hardwood (oak, ash, beech, elm, alder, birch and hornbeam). Technical properties of wood depend on its anatomical and chemical structure. Due to the porous structure, wood has high strength at low density (relative strength of wood is equal strength of the steel), has low thermal and sound conductivity. Mentioned feature constitutes technical value of any wood materials.

Thermal properties are the advantage of the wood construction, because wood is the best the heat insulator. It also has high levels of specific heat indicators. This indicators group for wood is significantly higher than for many plastics, almost twice then at brick and clay, the stone and concrete, and more than four times than that of iron and steel.

The advantage of the wood construction is its easiness of its processing. Wood defects include such factors as: a high hygroscopicity, swelling, shrinkage and cracking of wood and its flammability and low stability. The physical characteristics and mechanical properties of wood are different depending on its origin (hardwood, softwood), humidity and the analysed section (laterally or along the grain). Physical and mechanical properties of wood affect the possibilities of its use in construction.

The wood materials used in the construction industry are in the form of round wood (from which comes sawn wood used for the manufacture of building products) and wood-based materials (veneer, block board, chipboard, fibreboard, wood panels, flooring, shingles). One of the more popular wood-based materials currently used in the construction industry is: a solid wood construction in the spliced systems, wooden structures systems and glued laminated timber. Glued laminated plates are solid, consisting of cross-laid layers of wood material. The use of laminated wood provides a very good sound insulation and meets all the requirements for the fire safety. 1.1. Requirements for wooden constructions

Wood used in the construction should have moisture content in the range 18-19 %. It is understood that during construction process, usually lasting several weeks, wood dries in about 14 % for maximum strength, dimensional stability and do not cause warping of the building construction elements. The same applies to solar, summer weather. In the autumn and winter periods, a wood may increase its moisture content to 20-22 %.

Technologies related to the construction of both timber frame and prefabricated elements used in the energy-efficient houses construction also impose requirements for systems and components for the mechanical wood processing. It is required, that components should be four-side planed. Such treatment not only provides dimensional stability, shortens time of the building construction process, and decrease the labour costs. A four-side planning increases the resistance of the wooden building structure against the fire.

The wood should be dried in the drying chamber to decrease of insect threat. Studies conducted in the United States have shown that drying at high temperatures (around 60 °C) deprives the timber of all natural substances, which could be a breeding ground for pests of wood. The most serious and most common mistake in the case of the constructions carried out in the light wood-frame technology is the use of wet wood and not planed. Such timber has a negative impact not only structural strength, but also reduces the durability of the building. Examples of the risks posed by the use of wet wood for the construction of the building: − reducing the structural strength, wood of a tree freshly cut (with a moisture content greater

than 30 %) has a flexural strength of about 60-75 % less than wood with a moisture content below 18 %,

− rapid destruction of timber, closed in the wall and not being able to quickly dry, wood is brewing and exposure to blue stain, mold and fungi,


145

− destruction of the thermal insulation of external walls (moisture coming from the wood penetrates the insulation layer by reducing its insulating properties),

− cracking of plasterboard walls and ceilings, wooden parts shrink and twist during drying process.

1.2. The basis of the construction selection

Selection of building materials, in addition to physical, physical-chemical and mechanical properties, also includes architectural requirements and economic reasons. In general, factors determining the construction selection are following: the investor’s needs, type of coverage, bandwidth, load type, quality of material, connections’ types, chemical factors, architectural requirements, economic factors, and type of manufacturing, fabrication, and construction operating conditions.

Architectural requirements are related to architectural forms, which are affected by such factors as: the room assignment, lighting, ventilation, requirements for visibility or invisibility of the construction. Economic factors are associated closely with the construction typicality, type and level of performance and prefabrication. Cost performance in industrial design and their installation on the construction place are lower in comparison to the cost of the construction made directly in the construction place. The relatively lower cost is achieved by performing a typical industrial structures and particularly suitable for prefabrication. In addition, wooden structures are often chosen because of the possibility of obtaining more living space than at home with the same conditions, but the brick one. Wooden house with floor area of about 10 % smaller than a brick house can get the same living space.

Wooden structures have become more popular with investors, architects and construction companies because of the energy efficiency of wood, and thus its environmentally friendly nature. It was calculated, that the wooden construction of a timber wall with a height of 3 m and 30 m in length, consumes 3.5 times less energy and 20 times less water than the concrete and steel construction production. Wooden structures are also chosen because of the low coefficient of expansion due to temperature changes, which means that the deformation of the wood in the case of temperature increase is small (factor determining the size of losses in case of fire). 2. THE IDEA OF ENERGY-SAVING WOODEN HOUSE

The idea of the energy efficiency improvement is one of the priorities of the European Union policy, which covered all industry sectors, including the construction industry. It should be emphasized, that the construction and real estate sectors are responsible for approximately 40 % of the total energy consumption, approximately 30 % of the CO2 emissions and 40 % of the waste. To ensure a long term durability in the reduction of environmental impact, we do not only have to reduce energy consumption in new building constructions, we also need to ensure the LCA perspective and that future projects are carried out in line with these objectives. That’s why energy saving idea was introduced into construction sector.

Monitoring the progress and effects of European Union Directive implementation on the Energy Performance of Buildings Directive (EPBD) in 2006 and noticing inadequacy of the original solutions, the European Parliament in 2010 adopted changes to help improve the energy efficiency standard of new and existing buildings. Technologies currently applied in the construction industry have a strong orientation to the use of energy-efficient solutions for applied materials, as well as constructions that will ensure future savings in the building utilization. Both the European Union action to improve energy efficiency and seek innovative


146

solutions for architects and construction companies lead to make full use of the idea of energy-efficient construction.

The energy-saving house is a house that consumes less than 15 kWh/ (m² • Year). This is achieved by using a few special arrangements and meets certain conditions. The building must have a very good thermal insulation, the walls of proper thickness, windows and exterior doors with excellent thermal properties. There is also important tightness of the connections between the different parts of the building, in order to avoid thermal bridges. Architecture requires a compact body. The energy is obtained from renewable sources such as heat pumps and solar panels. The idea of the energy-saving house was presented in Figure 1.

Figure 1. The concept of the energy-saving house

The most clear indicator of the energy performance of the building's operating costs for

investor or the owner of the house are energy consumption, resulting from its energy, which is actually the energy consumed in the heating, ventilation, cooling possible, hot water and lighting facilities. Meeting these requirements can be ensured by the use of a wooden construction of the building.

3. CHARACTERISTIC OF CONSTRUCTIONS SUPPORTING ENERGY-SAVINGS

Wooden constructions used in Poland are mostly in the lightweight skeletal construction. They can be divided into: Canadian housing (also known as the American), Swedish and German. The different types of frame structures differ from each other thicknesses of certain elements.

A characteristic feature of this building type is light skeleton made of wood. Foundations, wall posts, beams and elements of the roof structure should have the same thickness, and the width is dependent on the destination of a particular item. Stratification in the exterior walls on the inside of the building in a lightweight skeletal construction is as follows: plasterboard (12.5 mm thickness), vapour barrier (vapour retarder), polyethylene foil with a thickness of 0.15 mm), wooden structure with a thickness of 140 mm filled with insulation, chipboard moisture-resistant (12 mm thickness), polypropylene foil, facade cladding. The wooden construction is a kind of frame, which is the housing for insulating materials (Figure 2). The thermal insulation of houses based on the frame structure is not determined by the thickness of the walls, but the quality of the insulation layer.


147

Figure 2. The wooden frame house construction

Another popular type of timber construction is log homes. Wood that is used for logs, it

must be dried in the drying chamber. This allows items to be resistant to deformation and its dimensions do not change. They are also immune to fungus, mildew and pests.

A third type of wood construction is energy efficient prefabricated wooden structure, which will be characterized in the following part of the elaboration. 3.1. Characteristics of prefabricated wooden house technology

Prefabrication involves preparation of the various components (prefabricated) of the building on the production floor. Prefabricated houses are made on the basis of the wooden framing, after which it resets the consecutive components (panels), which creates a complete home design. Ready components are assembled on-site construction of the house.

Prefabricated wooden constructions are made in the form of modules that are produced by factories and later transported to the construction place. Technology of prefabricated houses was widely used for the first time in Scandinavian countries. “Scandinavian houses”, “Canadian wood-frame houses” or “Finnish houses” - it's all cheap houses that have passed quality tests in much more difficult conditions than in Poland.

The walls of prefabricated wooden houses have skeletal structure (Figure 3). The space between structural elements is filled with insulating material, which also plays the role of thermal and acoustic insulation. The outer wall sheathing is OSB, secured by the windproof membrane. The facade is made of profiled boards, secured by fire-resistance, fungicides and insecticides. Cladding boards can be stacked horizontally, vertically or in a combination of these positions. The colour of the facade paint coatings is selected according to customer requirements. The outside walls are covered with chipboard covered with vapour foil and finished with plasterboard or cement-fibres. The module technology ensures the appropriate air exchange. Lightweight construction is very durable. The material which forms the walls, ceiling and roof are prepared from a pine wood with class II or III.


148

Figure 3. The prefabricated module used as the energy-saving wooden construction (Tadeks Fertighaus, Poland)

3.2. Specific solutions supporting energy-saving wooden house idea

The other type of prefabricated wooden construction is wooden element consist of wooden boards only (Figure 4, element 1). The wooden boards as single items-wooden layers (Figure 4, element 2), that are connected with applying of treenails arranged in a similar way as the chessboard (Figure 4, element 4). There is also a version with empty spaces between wooden boards to support energy-saving properties (Figure 4, elements 3a, 3b, 3c, 3d).

Figure 4. The prefabricated layered wooden element applied

in the energy-saving wooden construction (invention of Thoma Erwin, St. Johann/Pongau, Austria, 1998, A1205/98 used in Poland)

The analysed wooden construction supports energy saving properties in different ways by

using: treenail and avoiding using nails (which can be thermal bridges), avoiding bonding elements that requires chemical substances (environmentally friendly solution) and supporting construction durability.

The other solutions concern the connection of wooden modular elements (Figure 5). In order to simplify the module wooden constructions, in 1999, a building module was elaborated. It constitutes a part of the shell wall, which are cross-linked support bars with at least one spacer linker containing connecting of output beyond the lateral plane and lateral posts for the series connection of adjacent modules. Pivot joints are used for connecting neighbouring modules. The spacers are attached to the fittings carrier bars from their outer sides or in the middle, preferably centrally, along the through-drilled holes. Lightweight and simple design of the module allows the construction for efficient but stable skeletal material and load-bearing walls and partitions of buildings using the building for a variety of building materials.


149

Figure 5. The wooden building module (invention of Muszynski Arkadiusz, PL, WUP 09/07)

Therma-TEC PANELS are designed to the latest and modern standard of BS EN 1995-1-

1:2004 Eurocode 5 (which is now in force parallel with old BS 5268-2:2002). Therma-TEC PANELS were most probably the first in the UK to use spaced column designs as framing members, thereby reducing and minimizing the problems of thermal bridging caused by traditional solid stud members. Panels are designed to the Eurocode 5 standard within European Union regulations. Clear space between shafts and gussets is another unique property of Therma-TEC PANELS allowing the designers to hide all services in the panel without disturbing structural elements. Even big services, such as 110 mm soil pipes or 200 mm ventilation ducts, can easily be accommodated in the panel leaving enough space for insulation to reduce thermal bridges (Figure 6).

Figure 6. The innovative wooden frame house construction (Timber-TEC)

4. CONCLUSION

Analysis of chosen constructions applied in Polish energy-saving wooden construction is environmentally friendly during the whole design process. Those building solutions are characterized mostly with reducing thermal bridging effect reached by applying only wooden


150

connections of wooden elements in the entire construction. Presented systems are driving value of heat escape down to approximately 5 % of the wall area.

Analysed solutions are environmentally friendly because of the reducing of the amount of applied wood and possibility to recycling materials wasted in the result of building.

The wooden constructions in all cases are excellent thermal performance because of additional space gained for insulation. Typical U-value of panel element using fiberglass is in the range: 0.13÷0.15 W/m2K. Reduction of total wall thickness as a result of isolation and connection of the superstructure in one component causes economical savings as well such as: material cost savings, reduce costs and significantly accelerates the implementation of projects.

Acknowledgements: Research findings were elaborated within Visegrad Small Grant project No 11310223 called “WoodEMA. Visegrad innovations”. 5. REFERENCES BIČANIĆ, K.; JELAČIĆ D.; GAŠPARIĆ, V.; CAREV-LAŠKARIN, V.; KOCBEK-NIŽETIĆ, M. (2010):

Identitet poduzeća u preradi drva i proizvodnji namještaja Republike Hrvatske. Drvna Industrija 60 (3): pp. 145-153.

THÖRNQVIST, T. (2009): Wooden Ecobuildings – energy efficiency in LCA percepctive. School of Technology and Design. Reports No 61. Växjö university. Sweden.

PATENT No. PL 167079, Iwanaszko Krzysztof, Słowiński Tadeusz, Presz Krzysztof, Poland, 06.08.1991

PATENT No. EP 0214088 PATENT No. EP 0744507 Invention of Thoma Erwin, St. Johann/Pongau, Austria, 1998, A1205/98 used in Poland. Invention of Muszynski Arkadiusz, PL, WUP 09/07. Timber-TEC, the right of Maciej Winiarczyk trading as Timber-TEC to be identified as the author of

Therma-TEC PANEL has been asserted in accordance with the Copyright, Designs and Patents Act 1988.


151

Microclimatic Conditions for Healthy Sleep and Rest – Influenced by Science, Psychology and Design

SVOBODA Jaroslava – TAUBER Jiřía*

a Department of furniture, design and habitation, Mendel University in Brno, Czech Republic *Corresponding author: [email protected]

Abstract – This paper deals with the issue of healthy sleep and rest in relation to the various pollutions of an interior. The current residential environment is being increasingly polluted in varying degrees with certain amounts of emitting substances such as VOCs. The aim of this paper is a possible solution to the problem by ionization of the environment in order to achieve the best possible quality of the environment. Emphasis is placed on the design of the negative-ions generator and its appropriate placement in an interior.

ion / microclimate / emission / design 1. INTRODUCTION

The interior environment where people spend most of their time is being polluted with various polluting substances. Some of the main air-polluting substances are volatile organic compounds (VOCs) which are emitted, for example, by furniture (new furniture mainly), carpets, curtains and other decorative elements in an interior. These VOCs are the cause of diseases of civilization and therefore it is only natural to try to limit their negative impact on human organism. One of the possible ways to reduce emitted VOCs in the air is to remove them with negative atmospheric ions. And this method is explored in this paper.

2. ATMOSPHERIC IONS

The air which surrounds us both indoors and outdoors is being constantly more or less ionized. This means that the air contains a certain amount of loose atmospheric ions. The more polluted the air becomes, the higher amount of light ions, which are so desirable and necessary to people, turn into medium and heavy ions and consequently vanish. People, who are sensitive to weather changes, perceive the fluctuating concentration of ions in the air. Some of the common reactions are headaches, joint aches, or even mood changes, disruptions in sleep and overall tiredness.

Atmospheric ions are electrically charged molecules, parts of molecules or molecular clusters, which come into existence through ionization of gaseous components of the atmosphere. To ionize the air an ionizing energy is needed and the sources of such energy are constantly working on the terrestrial surface. Therefore the natural air is continuously ionized. There is no electrically neutral air in the nature and people are adapted for this condition in the long term. A certain amount of atmospheric ions in the environment is necessary so that people can feel at ease (Figure 1).


152

Figure 1. The ionization of air diagram (Jokl)

2.1. The division of ions

Ions are divided based on their polarity and weight.

Division of ions based on polarity: • Positive – represented by nitrogen ions in the nature • Negative – represented by oxygen ions and water-vapour ions

This fact is due to the composition of atmosphere, which contains 78 % of nitrogen, 21 %

of oxygen and the rest – about 1 % - is composed of water vapour and other gaseous substances. The process of ionization is constant (creation and expiration of ions) and each cycle lasts approximately 10-6 of a second.

Division of ions based on weight:

• Light – clusters of 10 to 30 molecules of high motility gasses, with a lifespan of a few seconds, which constantly come into existence. In terms of biological effect on man, these are some of the most important ions.

• Medium – clusters of hundreds of molecules with a lifespan of a few hundred hours.

• Heavy – clusters made out of as many as thousands of molecules, whose life expectation reaches weeks, usually containing “condensing nucleus”, i.e. particles of dust, smoke or fume. The heavier the condensing nucleus, the shorter the lifespan of a heavy ion.

Based on the above described division we can conclude that, the more polluted the air is, the larger amount of light ions, so needed by man, turn into medium and heavy ions, which consequently terminates their existence. Thus the quality of the air is measurable by the amount of light ions contained in it.

Such phenomenon is exploited when the air is being ionized artificially (with air ionizer), by increasing the amount of ions in the air which absorb more pollution, turn into heavy ions which sediment faster and as a result the air is being purified. 2.2. Expiration of ions

When two ions of opposite charges collide, they exchange electrons and become electrically neutral particles, hence they expire. This process occurs in the air, on solid surfaces and also within the interior and exterior environments of buildings.


153

3. ARTIFICIAL IONIZATION OF AIR

Nowadays, various home air ionizers can be found on the market. These are so-called ion generators, which produce either ions of both polarities, or they are constructed in such a way that positive ions are captured inside the generator and only negative ions are released. Thus the generator provides only those ions which are beneficial and required in terms of biological effect on man. Such generators operate according to various principles.

The first group consists of corona discharge ionizers. Ions are emitted by a metallic needle which is placed in such a way that allows easy dispersion of the created light negative ions into the air. A metallic emitter requires occasional maintenance as the air pollution smelts on its pike which then dulls and the production of ions decreases. The second group consists of carbon fibre ionizers, which currently represent the latest method for production of light negative ions. The emitter comprises fibbers made of clear carbon. Such fibbers need no maintenance as they do not produce any pollutants during permanent output. 4. SYSTEM FOR MONITORING THE IMPACT OF NEGATIVE IONS ON VOC

EMITTED BY PAINT

The ability of negative ions to decrease the amount of pollutants in the air was utilized during particular experiments monitoring the impact of negative ions on concentration of selected VOCs in surveyed air. Based on the results of the experiments a testing system was constructed (Figure 2), which monitored using the following method. First the air inside the testing system was polluted with a specific amount of selected paint or a thinner. Once polluted, the environment was then exposed to the effect of negative ions emitted from their source (Figure 3).The concentration of emitted negative ions can be measured by a special ion meter. The degree of air pollution inside the testing system is measured by a gas chromatograph which analyses the quality of the air immediately after pollution and then again after the effect of the defined concentration of negative ions.

The testing system comprises the following individual devices and equipment (source of negative ions, ion meter, ventilator, thermometer with moisture indicator, and pump with off take tubes).

Figure 2. Testing system Figure 3. Ionizer


154

Based on the results of the experiments, we can conclude that ionizing the polluted environment decreased the concentration of selected VOCs, namely ethyl acetate, benzene, 1-methoxypropane-2-ol, toluene, hexanal, n-butyl acetate, ethyl benzene, m/p-xylene, and styrene. Other compounds were identified in small amounts and their concentrations either decreased insignificantly or remained the same after ionization. Nitrocellulose paint was used to pollute the air (Figure 4).

Readings of the concentration of ions during individual stages of the monitoring inside the testing system:

• Unpolluted environment without ionization: approx. 0 negative ions/cm3 • Unpolluted environment with ionization: 15000-17000 negative ions/cm3 • Polluted environment without ionization: 2700 positive ions/cm3 • Polluted environment after ionization: 7000 negative ions/cm3

Figure 4. Graphic representation of the decrease of VOCs from nitrocellulose paint

5. UTILIZING THE RESULTS IN PRACTICE

A good research is the one which can be utilized in our lives, for example in production, or it can be appropriately applied within an interior. Therefore the benefit of this work becomes apparent when, for instance, utilizing an ionizer within an interior in order to increase the quality of the air by deployment of negative ions which consequently increases the quality of our health.

In the particular project, an ionizer was built into the construction of a tester bed. By utilizing the tester, quite specific conditions (microclimate) supporting healthy sleep and rest were achieved. A tester bed has an effect of pleasant environment and provides intimate space, which can affect our psychological tranquillity. The depicted version features tester as a free floating unit which is not fixed to the construction of the bed. Thereby we are provided with very airy and open space. The tester bed is not furnished with the old-style deluxe and heavy curtains, rather it is dressed with pellucid and special textile of certain permeability

Graphic representation of the decrease of VOCs

0

1000

2000

3000

4000

5000

[µg.m-3]

after pollution after spontaneous

decrease after ionization

ionizer off

after ionizationionizer on

after pollution after spontaneous decrease after ionization – ionizer off after ionization – ionizer on


155

which can be fitted to the bed in a number of ways, for example with Velcro. Depending on the interior in which the bed is to be placed and individual customer requirements, the bed can be equipped, apart from ionizer and air purifier, with a range of electrical accessories such as special lighting, acoustic speakers, etc. The design of the bed is modern and the material used is Makassar veneer with high gloss in combination with white high gloss (Figure 6).

It is necessary that the individual designs be understood from two viewpoints – design psychology and health – which are both priority of this work. This claim can be supported by one of the designs which were introduced at Mobitex – the international fair for furniture and interior design in 2008 where it was awarded Grand Prix for advanced technology and material (Figure 5).

Figure 5. The prototype bed with tester introduced at Mobitex in 2008

Figure 6. Tester bed with suspension canopy


156

The below depicted bed (Figure 7) is based on a circular ground plan and with circular shaped tester fitted directly above it. The tester opens through vertical axis. In this particular design the tester is in the form of a circular frame above the bed. The frame comprises three parts made, for example, of plastic monocoque. The rest of the sectors are formed with steel bars and textile tightened between them. These textile sectors are guided by conductor rods around the perimeter of the bed. When opened the textile draws together in a shirring. An air purifier with ionizer, lights and speakers are fitted in the top part of the canopy (Figure 7).

Figure 7. Circular design with futuristic concept 6. CONCLUSION

The purpose of this paper was to point out the issue of healthy sleep and rest, which are more than often affected by various microclimatic conditions. The above stated issue, therefore, has been analysed from three different viewpoints – science, psychology and design. The scientific findings acquired through the previously explained experiments and applied in the design of the tester bed, which initiated a new design with additional functions, with crucial impact on the mental state of man. Such facility is beneficial not only to people with allergies or ill people, but also to healthy people, who appreciate the possibility to regulate the quality of the air. 7. REFERENCES BRUNECKY, P. (1998): Domiciologie, Brno: MZLU, ISBN 80-7157-307-8. JOKL, M. (2002): Zdrave obytne a pracovni prostredi. [s.l.] : [s.n.], 2002. LAJCIKOVA, A. (2007): Syndrom nemocnych budov, Kancelar, 10, c.2, s. 38-39. SALTHAMMER , T.; WENSING, M. (2001): Emissionsprüfkammern und -zellen zur Charakterisierung

der Freisetzung flüchtiger organischer Verbindungen aus Produkten für den Innenraum. In MORISKE, H.J. und TUROWSKI, E.: Handbuch für Bioklima und Lufthygiene, III-6.4.1, ECOMED-Verlag, Landsberg.

SPENGLER, J.; Mccartny, F.; Samet, M. (2001): Indoor Air Quality Handbook, McGraw-Hill Professional, ISBN 9780074455494.


157

Possibilities of CNC Manufacturing with Regard to Furniture Design

ŠIMEK Milana*– KOŘENÝ Adama – DLAUHÝ Zdeněka – MIHAILOVI Ć Stefana

a Faculty of Forestry and Wood Technology, Mendel University in Brno, Czech Republic


Abstract – The research deals with numerous possibilities for, and aspects of, CNC (Computer Numerical Control) manufacturing in regard to industrial furniture design. The objective of this work is the evaluation of certain parameters of CNC furniture production technology, more precisely the parameters of CAM (Computer Aided Manufacturing) processing with respect to a given type of furniture – a work chair, constructed as a flat pack product. Work chair was chosen because it represents a complex, functional and purely industrial furniture design. Basic ergonomic data are described in relation to working while seated, then the specific approach to flat pack furniture construction optimized for CNC manufacturing is introduced, as well as some examples of work chairs. Flat pack furniture is becoming more and more popular, especially for its economy and ease of production, transport and stocking. The outcome of the present contribution is to collect knowledge about CNC / CAM technology and options for CNC optimized furniture design, offering the employment of CNC technology capacities, related innovations and better mechanical resistance of the final product.

CNC / CAM / furniture / manufacturing / design / flat pack 1. INTRODUCTION

The most important innovation of the 19th century in the furniture industry was perhaps

the industrial wood bending, which is associated with the name of Michael Thonet. He came up with the idea of saving shipping space, and transport knock-down chairs. His most popular chairs, made of bent wood (Figure 1) were sent thanks to dismountability across the ocean in a box with a minimum of unused space (Figure 2). The concept of furniture dismountability was re-introduced by Ikea in the 50`s of 20th century, by the „Lovet“ table. Innovation of Ikea was assembly by a final customer. Next step which is crucial is the introduction of computer-controlled machines, i.e. CNC machining technology. CNC machining technology has been developed in the 40`s and 50`s of the 20 century in the United States. Main advantages of a CNC technology are automation of the manufacturing process, high accuracy and speed of processing, high reliability and versatility with low maintenance and exclusion of technology breaks for new settings. On the other hand main disadvantages are higher purchasing and operating costs, higher knowledge demands on the operator and lower production speed compared to large series production of the various specialized machines (HIGLEY, 2002).

This historical development and different possibilities of CNC in comparison with traditional machines allow us to develop furniture which can be specific in its construction and technology. This type of furniture is manufactured and shaped directly with CNC, construction is dismountable and no fittings are used. All advantages and disadvantages of CNC technology mentioned above are true in general (RAO, 2010). But there are always some conditions which have to be fulfilled to make given advantages strong or disadvantages weak. Number of axis of CNC determines its possibility to operate in different planes (SMID , 2006). Nesting (of machined parts) on the other hand supports strong aspect of CNC production – economical material usage (ALBERT, 2006).


158

Figure 1. and 2. Parts of disassembled chair No. 14 (left) and a transport box with its many parts

(right) 2. CAM/CAD SOFTWARE

The software used in the furniture industry can normally be put into three basic categories which can more or less be used together. They are:

• Common modelling programs for volumetric or flat models, including, if desired, the construction of macros for the furniture industry.

• Software exclusively for the creation of furniture and interiors • Software created for running machinery – WOP (wood oriented programming

software) Ordinary modelling programs and their connection to CAM systems: This type of program offers universal solutions for preparing the production of any item including furniture. These programs feature specialized modules for various classes of design work. Their obvious advantage is that they make it possible to define any object with complete freedom, and in combination with a CAM module, to precisely define machining operations, trajectories, and a detailed production sequence. Considering the character of these programs, they are not advantageous for common products in the furniture industry when objects are produced first and only later identified. Defining ordinary furniture pieces is too slow with these programs; they are vulnerable to error and they contain an insufficient quantity of readable data about an object. Their universality, on the other hand, makes them advantageous for the development of completely new procedures.

Specialized systems: These are characterized by a narrow focus on furniture. Then can be based on volumetric modelling programs and delineate manufactured models – a less advantageous way, requiring similar objects to be created repeatedly. Their second principle rests on defining generic construction parameters, on the basis of which objects can then be created. This narrow focus means it is possible to use a greater or lesser number of the machines commonly used in the furniture industry. The capabilities of a system are usually predetermined and the concrete type of system will dictate the possibilities for general application. However, it is not normally possible to come up with entirely new and hitherto unexplored processes, as it is with ordinary modelling programs. The advantage of these specialized systems lies in the way they can be used in everyday production, where the


159

number of usable processes for milling is limited, and so these programs offer a systemic solution for production.

WOP Software: Machines for making furniture are equipped with these programs, which permit the user to input information and control the basic functions of the machine. This software facilitates working with ordinary macros such as drilling, milling, mortising, cutting, control of specialized aggregates, and other possible operations. Software of this type is usually specifically designed for each particular producer, or even particular machine, and makes possible the simple control of all of the machine's functions. As noted by author XU (2004), ISO code is characterized by problematic readability and non-adjustability during production. WOP programs designed to control furniture-making machines do not normally permit advanced definition or processing, and when permitted, this definition can sometimes be too complicated. This software, at the same time, is not conceived for systemic solutions and is thus used only by machine operators; these programs may contain individual components common to all products that are prepared by technical office workers.

The above-mentioned systems can overlap or collaborate in various areas. It is nevertheless clear that despite this overlap, a concrete product is really only designed for use in one area. WOP – basic machining, Ordinary modeller – free design and hitherto untested processes, specialized systems – fast and effective processing of a large quantity of information. Table 1 gives more precise data for evaluating the chosen programs.

For a given project it is possible to use all three types of software. WOP software serves to set production machines and is always indispensible for running them. It can be used for the final adjustments of a program. An ordinary modelling program can serve for quick design of a solution and for optimization of trajectories. Specialized software can secure production by conventional means. In the case of a successful design and interest on the part of the end user, a design can be created for implementing a process even in this specialized solution.


160


161

3. FLAT PACK FURNITURE AND CNC TECHNOLOGY

Flat pack furniture is a kind of furniture produced and prepared with a view to fast and simple assembly, otherwise known as RTA (ready-to-assemble). As the name indicates, flat pack furniture is made directly from flat materials (sheet metal, wooden boards, even cardboard). Its features are the most efficient possible use of materials, compact design, and simple assembly. It can often be classified as environmentally-friendly as well. The advantage of flat pack furniture (considering today's nomadic lifestyle and the struggle with cramped spaces) is found in the fact that it can be easily disassembled and transported, is space efficient, has a small number of components and is simple to assemble (without complicated tools). At the same time, this type of furniture is a cheaper alternative to standard furniture.

In this age of technical progress, a whole range of technologies are available which can be used to produce flat pack furniture. The most widely used are rapid manufacturing (rapid prototyping, 3D print), CNC routers, laser cutting, water jet cutting and others. Each has its own specific features and the form of the resulting product is directly dependent on the specific technology used.

The construction of flat pack furniture is characterized by the fact that it normally does not require the use of complicated tools, joining components, or glue. Most often its construction is predicated on a combination of friction and pressure between surfaces, holding the entire piece together. Flat pack furniture uses the principle of male/female joints or slot/pin joints. The most frequently used joints are mortise and tenon joints, finger joints, and dovetail joints. The choice of joint type will depend on the choice of material. The chosen material, with its physical and mechanical properties, directly affects the construction and thereby even the final appearance of the product. 3.1. Trends

A growing need has recently emerged to change the rigid, static shapes that are typical for flat pack furniture into dynamic and more user-friendly-shaped products. Geometrically shaped objects are being transformed into organic products characterized by elegant curves and interesting patterns. The perforation of surfaces helps to achieve flexible properties and to bend wooden boards in order to create various shapes (Figures 4, 5, 6). It is thus possible to ensure not only ergonomic shaping but also the springing of a given product or its components (chair seats). However, geometric shapes evolve as well, imitating natural shapes in the form of crystal structures (Figure 8) or lightweight stylized insect-like shapes (Figure 7).

Apart from the trends in the shapes of furniture, quite interesting services – portals that offer the plans and data of products designed for production – have also emerged lately. One only needs to choose a design, and the portal administrator will send the data in the form of source code to the nearest factory (www.ponoko.com). Projects like Sketch Chair (Figure 3) that allows the users to design their own chair, in the spirit of the flat pack philosophy, are also interesting. The project is distributed as open-source software and is suitable for both designers and the general public.


162

Figure 3. SketchChair by Diatom Studio

(http://www.sketchchair.cc) Figure 4. Andy Kem Breakplane Table

(www.seeartdesign.com/artists/andy-kem)

Figure 5. Spring Wood by Carolien Laro

(http://www.dezeen.com) Figure 6. Perforation, Flexi

(http://www.woodworkingtalk.com)

Figure 7. Angled plywood chair by Emiliano

Gody (http://blog.lrytas.lt/interjeras) Figure 8. Chair 23D by Gustav

Düsing(http://gustav-duesing.com)

4. ERGONOMICS

Experts from all over the world have agreed that the upright sitting posture is the ideal one. In Figure 9, selected drawings illustrating “the right posture” are displayed (DK 1+2 and S). The ISO and CEN drawings serve as a basis for international standardization and are used to educate furniture designers. Although these postures look very satisfactorily on the picture, it must be mentioned that hardly anybody can actually sit like that for a long time. This upright sitting posture or right-angle posture is basically a short physical exercise that does


163

not have anything in common with a real working posture. As is widely known, the human body allows a large range of various postures. So why do standardization committees choose a single sitting posture as a reference for their standards? This question is very important since sitting is a dominant activity of our everyday life.

Figure 9. Furniture standardization – “the

right posture” Figure 10. Leaning chair

4.1. Working positions

When sitting in the front posture, the body leans forward. The weight of the body that rests on the chair seat moves forward, onto the tailbone and hamstrings. Some types of sitting furniture, where the angle of the chair seat is adjustable, allow the front sitting posture with the back upright which may be useful for some working activities. This posture helps maintain the upright posture by tilting the pelvis forward. Students have always been very inventive when it comes to finding alternative postures in order to avoid painful sitting. Their sitting postures when trying to find less painful positions are definitely worth observing. This may be the field where we will find out what sitting furniture is supposed to look like. Most kids quickly discover that sitting on a chair is much more comfortable when the chair is leaned forward, thus avoiding bending their backs (Figure 10).

A B C D E

Figure 11. Resting positions by J.J.Keegan Figure 12. Sitting positions for work activities

In Figure 11, the back-resting position when e.g. lying on your side is displayed. C. Hip joint at a 45˚ angle. This is the resting position of the hip joint when both front and back thigh muscles are balance and the lumbar lordosis retains its natural concave bent.

When sitting in the position where the femur and the spine form an angle of 90˚ and the body is leaned slightly back (Figure 12 A), the work area may be reached by:


164

• bending the spine in the lumbar region by approximately 20˚ which leads to back rounding and more pressure on the vertebral discs B

• increasing the angle of knees by 20 ˚C while keeping the back straight. In this case however, the chair seat puts pressure on the back thigh muscles, which is not ideal. For a full effect, the chair seat must be leaned forward E. The height of the desk must be raised so that the chair-to-desk ratio is approximately 58 cm to 86 cm (MANDAL , 1985).

Long-term comfortable sitting may be achieved by: • Decreasing energy consumption This may be achieved through proper body support. However, the influence of this

precaution is limited, because even energetically less demanding muscle activities may cause the accumulation of local fatigue, leading to the quick development of overall fatigue.

• The possibility of changing positions According to some opinions, the surface that fits the sitting parts of a human body is the

optimum sitting surface. The truth is that to sit on such a surface feels very comfortable but after a while, the feel of discomfort and the urge to change the sitting position appear. However, changing the position is impossible due to the shape of the sitting surface. An ideal support for our body in a single position definitely isn’t the key to comfort. Variation is very important (Figure 13). We like changing positions because it is completely unnatural for us to remain in the very same position for a long time. Each body part has its favourite position. So trying to define which position is the best for us is completely pointless. The best position is always the next one. Even the best position recommended by the best expert becomes uncomfortable after some time (OPSVIK, 2009).

Figure 13. Variations (sketch by PETER OPSVIK)

Comfortable sitting requires the ability of a user to change positions often using as little energy as possible. The possibility of changing position while working supports the dynamics of sitting, thus strengthening back and abdominal muscles. It decreases the occurrence of back pain and helps increase overall conditioning. Overall satisfaction may thus be achieved. And that’s why a work chair should allow a user not only to change positions, if necessary, but also to inspire him to do so through its form, whether directly or indirectly.

5. DISCUSSION / CONCLUSION

The aim has been to present a concept of furniture design based on the connection of technologies, recent advances in the field of the ergonomics of sitting, and parametric design.


165

Parametric design currently represents what most industries are trying to achieve – not only does it save resources, but it also increases competitive strength and stimulates innovation (SONG – GAZO, 2013; ALAGIĆ, 2011). In the furniture industry and timber trade, this tendency may be observed mainly in the field of education and innovation. This is due to the fact that one of the specific features of parametric designs is usually innovative design that is not accepted by every customer. And due also to the fact that furniture, unlike other industrial products, doesn’t have such well-developed legislation dealing with the placement of new products on the market, new products struggle to break into the market. Acknowledgements: The authors thank the Internal Grant Agency (IGA) of Mendel University in Brno, Faculty of Forestry and Wood Technology, project IGA 57/2013. 6. REFERENCES ALAGIĆ, I. (2011): How to Achieve Excellence, Innovation and Quality in the Wood Processing

Industry in B&H, 7. Naučno-stručni skup sa međunarodnim učešćem ”KVALITET 2011”, Neum, B&H, 1. – 4. June 2011.

ALBERT, A. (2006): Understanding CNC Routers, FP Innovations, Forintek, p. 105. URL: http://www.solutionsforwood.ca/_docs/reports/UnderstandingCNCRouters.pdf

DIATOM STUDIO, (2012): Sketch Chair. URL: http://www.sketchchair.cc

DÜSING, G. (2012): Chair 23D. URL: http://gustav-duesing.com/chairsgallerie.html

GODY, E. (2009): Angled Plywood Chair. URL: http://www.interior-and-design.com/ 2009/04/14/angled-plywood-chairs/

HIGLEY, J. B. (2002): CNC applications. Calumet., Purdue University, Indiana, Cited: 15. 5. 2013, URL: http://technology.calumet.purdue.edu/met/mfet/275/

JPANICHELLA (2011): Perforation. Flexi, URL: http://www.woodworkingtalk.com/f9/my-senior-capstone-cnc-flatpack-furniture-38190/

KEM, A. (2010): Breakplane Table. URL: http:// www.seeartdesign.com/artists/andy-kem/

LARO, C. (2011): Spring Wood. URL: http://www.dezeen.com/2011/01/05/spring-wood-by-carolien-laro

MANDAL , A.C. (1985): The Seated Man: Homo Sedens. Dafnia Publications, Copenhagen, ISBN 87-982017-1-9.

OPSVIK, P. (2009): Rethinking Sitting. W.W. Norton & Company, New York, London, ISBN 978-0-393 73288-97.

PONOKO (2013): The world easiest making system, Available at: https://www.ponoko.com/ RAO, P.N. (2010): Cad/Cam: Principles & Applications, Tata McGraw-Hill Education, ISBN 978-

0070681934, p. 784. SMID , P. (2006): CNC programming techniques: an insider's guide to effective methods and

applications. New York : Industrial Press, 2006. ISBN: 978-0831131852. SONG, M.; GAZO, R. (2013): Competitiveness of US Household and Office Furniture Industry,

International Journal of Economics and Management Engineering, Apr. 2013, Vol. 3 (2), pp. 47-55.

XU, X.W. (2004): Striving for a total integration of CAD, CAPP, CAM and CNC, Robotics and Computer-Integrated Manufacturing, Elsevier, 20, pp. 101–109.


167

Influence of Moisture Content on the Strength of Welded Joints

ŽUPČIĆ Ivicaa*– GRBAC Ivicaa – BOGNER Andrijaa – ŽULJ Ivana – LJULJKA Borisa a Department for furniture and wood products, Faculty of forestry, University of Zagreb, Zagreb, Croatia

*Corresponding author: [email protected] Abstract –Wood welding is a process which includes both chemical and physical reactions. Heat is formed during friction, melting and softening of the structure of wood. When the melt cools, a firm joint is formed. Dowels are welded to the surface using rotary welding techniques. This paper studies the influence of moisture content on the substrate and the impact of the dowels on the shear strength of welded joints. This study covered nine groups of samples with different moisture contents and parallel and perpendicular orientations of fibres in the substrate and dowels. The best results were recorded for the sample group (P8M8P) with 7.7 % moisture content in the substrate and dowel. The group of samples with low moisture content (P4M8O) had the worst results, with 4.8 % to 7.7 % substrate and dowel moisture content, respectively. It was concluded that the moisture content in the substrate is the most important parameter for the quality of weld, while the moisture content of the dowel does not play such an important role.

beech wood / wood welding / moisture content / dowel / strength / joints 1. INTRODUCTION

Welding of wood is a process which creates chemical and physical reactions, heat is formed by friction which melts and softens the structure of wood, and a firm joint is formed by cooling of the melt.

The welded samples with 12 % moisture content in wood contained moisture in two different forms, i.e. bound water and constitutional water (ROWELL – LEVAN-GREEN, 2005). Bound water or hydroscopic water is linked by hydrogen bonds between molecules of water and hydroxyl groups in wood. Structural water constitutes the bonds of water molecules formed by reactions of wood components at high temperatures. Water molecules (bound water) are bound into polysaccharides with the smallest pure sizes and the largest content of free molecular groups. These are mainly wood polyoses and amorphous cellulose (SHAFIZADEX , 1963).

During rotational welding of the dowel into the hole, various methods are used to ensure joint strength. Some of those methods include: the use of ethylene glycol (also known as a plasticizer of lignin) and other compounds, welding warm (heated) dowel and dowel with low moisture content (0 to 1 %) and drilling of multistage holes (at a certain depth a smaller diameter hole is drilled) (KANAZAWA et al., 2005). The research is based on small tightness during welding at a depth of 30 mm. Groove dowels made of commercial type of beech, 10 mm in diameter and 8 cm in length, are welded into a hole 9 mm in diameter with rotation frequency of 1200 min-1. At a certain depth, dowel rotation is stopped, and the insertion pressure is kept for a short period of time. Control samples with 12 % moisture content reached an embedded force of 1894 N, while samples with dowel heated to 100 ºC and moisture content of 1 % reached an embedded force of 2986 N. This increase in embedded force, i.e. joint strength by a little over 36 % is certainly significant. For dowels that had a cross cut top, the embedded force increase was 41 %.

GANNE-CHEDEVILLE et al. (2005) researched important parameters in rotational dowel welding (assembling joining). GANNE-CHEDEVILLE also measured the moment during the welding of a dowel into the base, (it was far below the dowel torsion moment) which enabled an easy insertion of the dowel. Their research used beech groove dowels 10 mm in diameter


168

and welded with two rotation frequencies (1165 and 1515 min-1). The elements the dowel was welded into were made of beech and pine wood with an 8 mm diameter hole. The research results showed an increase in joint strength with reduced moisture content when higher rotation frequency was used. The best results in terms of strength were obtained with 0 % moisture content and rotation frequency of 1515 min-1. By reducing moisture content in the dowel and at 1515 rpm, joint strength was considerably increased compared to rotation frequency of 1165 rpm. The best result in embedded force was achieved by the combination of rotation frequency of 1515 rpm, using dowel which was welded into beech base and had 0 % moisture content, heated to 80 ºC and not treated with ethylene glycol. Average embedded force was 3184 N. Control samples were glued with PVA, and average embedded force of the dowel was 3701 N.

Improvement in joint strength was achieved by heating the dowel at 100 ºC to moisture content of 1.5 % (PIZZI et al., 2004). Then the heated dowel was welded into the base using rotational method. The average embedded force of groove dowel with 9 mm in diameter, welded at 30 mm depth with rotation frequency of 1200 min-1, equals 3134 N. Joint strength was equal to that of dowels glued with PVA. However, using the welding method the strength is achieved in a few minutes, while PVA takes 24 hours to show similar results.

Latitudinal joining of groove joints using linear vibration welding was researched by OMRANI et al. (2009). In the course of linear vibration welding groove joints easily evaporate water from the compound thus increasing the welding surface. The research results clearly show that increased grooved surface did not increase the strength of the joint, but it was rather decreased. This justifies the use of straight joints. The cause of decreased strength of groove joints are cracks that appear in the wood. The water evaporating joint had an increase in strength, but a statistically insignificant one. This confirms the thesis of water evaporation and change in moisture content of the wood.

The two wooden elements glued together are expected to reach the required strength of the whole structure. Moisture content in the wood has a high impact on the quality and the strength of the joint. Depending on the technology or conditions of use, the moisture content in the wood (for gluing) is between 8 and 14 %. Individual elements which are to be glued together must have even moisture content. If it differs by more than 2 %, this can cause stress in the joint. This stress can result in broken joints, without additional external stress (RIVER –

OKKONEN, 1991). BINIEK AND SMARDZEWSKI (1987) also researched the influence of wood moisture

content on the strength of glued joints. Increasing wood moisture content from 11.6 % to 18.1 % reduces the joint strength by 20 %. With an increase of moisture content to 35 %, the strength reduces to 75 %.

The aim of the research was to determine the influence of various levels of moisture content in the base and dower on the strength of a welded joint. The optimum moisture content in the base and dower is expected to be around 8 % (the same as with glued wood), and higher or lower moisture content will not decrease the embedded force, i.e. the strength of the joint. 2. MATERIALS AND WORK METHODS

2.1. Samples, welding parameters and moisture content

The study was conducted at the Faculty of Forestry of the University of Zagreb. Beech samples with the dimensions of 200x30x30 mm were used for welding dowels vertically to the fibre orientation with three holes pierced in each sample. The samples with a dowel welded in the fibre orientation had three holes drilled in the front part with the dimensions of 30x30x64 mm. Upon welding, samples were cut vertically into two identical pieces. Average


169

density (ρ0) of beech was 0.74 g/cm³ (min. 0.60 g/cm³, max. 0.85 g/cm³) determined pursuant to the HRN ISO 3131: 1999 (Croatian standard for determination of wood density for the purpose of examining physical and mechanical properties of wood). Average wood ring width was 2.81 mm. Grooved dowels were 120 mm in length and welded into the pierce 20 mm deep with the rotation frequency of 1520 min-1 (the same frequency was used for welding all sample types). Average welding duration was 0.87 s with the tightness of 2.02 mm.

This study used three levels of moisture content: 4.86 %, 7.74 % and 14.55 %. Moisture content was defined pursuant to the HRN ISO 3130: 1999 (Croatian standard for determination of water content for the purpose of examining physical and mechanical properties of wood).

The bases and dowels with lowered moisture content were first dried at the temperature ranging from 103±2 °C to 0 % moisture content. The samples were then conditioned for 2 days and stored in a hermetically sealed receptacle (during the period of 25 days prior to welding) containing silicates in order to get moisture content evenly distributed on the sample and prevent it from further absorption of moisture and swelling. All the samples prepared in this way reached the average moisture content of 4.86 % (min. 4.04 %, max. 5.69 %).

The preparation of bases and dowels with the average moisture content of 7.74 % (min. 6.79 %, max. 8.89 %) was carried out on the samples conditioned during the period of one month in laboratory conditions (23±2 °C temperature and relative humidity of 50±5 %).

The preparation of samples with an increased moisture content of 14.55 % (min. 14.24 %, max. 14.73 %) was carried out on the samples conditioned in the air-handling unit under the temperature of 20 °C and relative humidity of 92 % and conditioning took place until reaching the appropriate moisture content for the samples (approximately 15 days).

Figure 1. The sample used for measuring the embedded force for dowels welded vertically to the fibre

orientation

Figure 2. The sample sawn in order to show the joint used for measuring the embedded force for

dowels welded in the fibre orientation


170

Table 1. List of samples and their codes

Code Description

P4M4O Samples with a lowered moisture content of 4.8 % in the base and dowel, welded vertically on the fibres

P8M8O Samples with moisture content of 7.7 % both in the base and in the dowel, welded vertically on the fibres

P14M14O Samples with an increased moisture content of 14.6 % in the base and dowel, welded vertically on the fibres

P4M8O Samples with a lowered moisture content of 4.8 % in the base and a moisture content of 7.7 % in the dowel, welded vertically on the fibres

P8M4O Samples with moisture content of 7.7 % in the base and a lowered moisture content of 4.8 % in the dowel, welded vertically on the fibres

P4M4P Samples with a lowered moisture content of 4 % both in the base and in the dowel, welded in the fibre orientation

P8M8P Samples with moisture content of 7.7 % in the base and the dowel, welded in the fibre orientation

P4M8P Samples with a lowered moisture content of 4.8 % in the base and a moisture content of 7.7 % in the dowel, welded in the fibre orientation

P8M4P Samples with moisture content of 7.7 % in the base and a lowered moisture content of 4.8 % in the dowel, welded in the fibre orientation

2.2. Test method

After welding, the samples were conditioned for 20 days (23 °C temperature, relative humidity of 50 %) and the measurements of the embedded force were initiated on a universal mechanical testing machine with testing time shift of 5 mm/min. Computers were used for measuring force and lag guaranteeing accuracy and preciseness of all values measured. For the purpose of this study 270 samples were welded whereas 242 correctly welded samples without any cracks were used for further study. Cracks and breaks appeared on 28 samples which, consequently, could not have been used for further study.

3. RESULTS AND DISCUSSION

The results of this study are presented in Table 2 and Figure 3. The study results indicate that the strongest embedded force is linked with the samples with a moisture content of 7.7 % in the base and 4.8 % (P8M4P) in the dowel as well as the samples with a moisture content of 7.7 % (P8M8P) in the base and the dowel. For both sample groups the dowel was welded in the fibre orientation. When a dowel was welded vertically to the fibres the best results were obtained for samples with a moisture content of 4.8 % (P4M4O) in both the base and the dowel. The poorest results are linked to samples with moisture content of 4.8 % in the base and moisture content of 7.7 % in the dowel.

Study results do not match the results obtained by GANNE – CHEDEVILLE et al. in 2005. The results obtained in their research indicated higher values for the embedded force in dowels with 0 % moisture content welded in a beech base in comparison to those with a moisture content of 12 %. The study conveyed by KANAZAWA et al. (2005) also indicates an increase of embedded force for dried dowels with the moisture content of 1 % in relation to the control samples (dowels) with a moisture content of 12 %. The reason for the variation in the distribution of study results is linked to the fact that different welding factors were applied. Duration of the welding process and rotation frequency are among the most important welding factors and they considerably reflect on the strength of a joint. Moisture content also influences the strength of a joint but in the scope of the study considerably less than the main welding factors (welding duration, rotation frequency, pierce and welding


171

depth). It is presumable that the welding of samples with the moisture content of 15 % up to the saturation point of fibres would lead to the decreased strength of a joint.

Wood heating (wood was dried in a drying oven under the temperature of 103±2 °C) leads to chemical reactions linked to the main wood components (lignin, wood polyoses and even celluloses). MAMOŇOVÁ et al. (2002) studied microscopic changes in breech structure after treating the samples in the water boiling from 100 to 140 ºC. Their study results indicate condensation of lignin and decomposition of wood polyoses. Lignin penetrates (migrates) through a cell’s membrane at 100 ºC and 10 minutes of treatment forming a drop-like structure in a cell’s lumen. These microscopic alternations are followed by chemical reactions in the main wood components. The analysis of hydrolysates indicates reactions linked with the dissolution of acid components at the temperature of 100 ºC. Their concentration increases with increased temperature and duration of a treatment. The analysis of saccharides confirms the stability of my-contact at the temperature ranging from 100 to 110 ºC, and depolymerisation starts at the temperature higher than 140 ºC. Non-crystallized cellulosic components are present in small quantities under the temperature of 100 ºC. All these changes have a significant impact on the welding process and the strength of welded joints.

The objective of this study was to investigate the possibility of welding samples with various moisture contents. Researched ranges moisture content in the wood that can be found in practice. Since those are relatively small ranges, this study should certainly extend to welding wood with higher moisture content and lower so we can assume that the distribution of embedded force was divided differently. The results of this study indicate that the entire scope of various moisture contents under the survey proved to be optimal for welding.

This study used the optimal welding parameters since the research results and the insight in the present scientific data (ŽUPČIĆ et al., 2010) indicates that the embedded force (strength of a welded joint) reached the maximal values with the tightness ranging from 2 to 2.6 mm. These values are at the same time optimal tightness for the rotational welding of a dowel during the period of 0.8 and with the rotation frequency of 1520 min-1 (ŽUPČIĆ, 2010; ŽUPČIĆ et al., 2011). According to PIZZI et al. (2003), the optimal tightness is 2 mm since any increase or decrease of tightness results in a decrease of embedded force (with the rotation frequency of 1200 min-1). Table 2. Descriptive statistics of the results obtained for embedded force in relation to moisture content and welding orientation

Sample code

Arithmetic mean of embedded

force (N)

Sample number

Standard deviation of

embedded force (N)

Min. embedded

force (N)

Max. embedded

force (N)

P4M4O 5020.7 29 489.7 3820.0 6170.0 P8M8O 4623.0 30 366.7 3740.0 5340.0 P14M14O 4322.1 28 428.4 3480.0 5320.0 P4M8O 2563.1 29 444.8 1680.0 3520.0 P8M4O 4689.7 29 393.7 3700.0 5310.0 P4M4P 4477.5 21 428.6 3820.0 5180.0 P8M8P 5271.4 29 522.2 4250.0 6080.0 P4M8P 3341.0 20 726.8 1240.0 4292.0 P8M4P 5356.9 27 478.0 4010.0 6040.0 All groups 4438.8 242 989.7 1240.0 6170.0


172

Mean Mean±SE Mean±1,96*SE

P4M4OP8M8O

P14M14OP4M8O

P8M4OP4M4P

P8M8PP4M8P

P8M4P

Code

2000

2500

3000

3500

4000

4500

5000

5500

6000

Em

bedd

ed fo

rce

(N)

Figure 3. Influence of moisture content on the base and dowel and welding orientation (in the same direction and vertically to the fibre orientation in respect of the embedded force in rotational dowel

welding)

4. CONCLUSION The study indicates that beech dowels can be successfully welded into a beech base in a

controlled environment with different values for moisture content (rotation frequency of 1520 min-1, welding time of 0.87 s and tightness of 2.02 mm).

The impact of moisture content on the strength of a joint is not univocally defined. For dowels welded vertically to the fibre orientation, the embedded force is less powerful (statistically relevant) with an increase in moisture content of 4.8 to 14.6 %. For dowels welded in parallel with the fibre orientation, the results indicate stronger embedded force (statistically relevant) with an increase in moisture content of 4.8 to 7.7 %.

The samples with variable moisture content in the base and in the dowel indicated important variations (statistically relevant) for the strength of a joint (the same applies to wood treated with adhesives). The embedded force increased with an increase in the moisture content of the base ranging from 4.8 to 7.7 % and a decrease in the moisture content lf the dowel ranging from 7.7 to 4.8 %. The moisture content in the base plays a very significant role in relation to the moisture content in the dowel. 5. REFERENCES BINIEK , P.; SMARDZEWSKI, J. (1987): Effect of simultaneous changes in several factors on the

strength of fork-tenoned joints. Przemysl Drzewny, 38 (11): pp. 6-8. GANNE-CHEDEVILLE, C.; PIZZI , A.; THOMAS, A.; LEBAN, J. M.; BOCQUET, J. F.; DESPRES, A.;

MANSOURI, H. (2005): Parameter interactions in two-block welding and the wood nail concept in wood dowel welding. J Adhesion Sci. Technol., 19 (13-14): pp. 1157-1174.


173

KANAZAWA , F.; PIZZI , A., PROPERZI, M.; DELMOTTE, L.; PICHELIN, F. (2005): Parameters influencing wood-dowel welding by high-speed rotation. J. Adhesion Sci. Technol., 19 (12): pp. 1025-1038.

MAMONOVA, M.; LAUROVA, M.; NEMČKOVA, V. (2002): Analysis of structure of beech wood subjected to hydrothermal treatment. Wood Structure and Properties, Zvolen, Slovakia, 51-55.

OMRANI , P.; MANSOURI, H. R.; PIZZI , A. (2009): Linear welding of grooved wood surface. Eur. J. Wood Prod., 67 (4): pp. 479-481.

PIZZI , A.; PROPERZI, M.; LEBAN, J.M.; ZANETTI, M.; PICHELIN, F. (2003): Mechanically – induced wood welding. Maderas. Cienca y tecnologia, 5 (2): pp. 101 - 106.

PIZZI . A.; LEBAN, J. M.; KANAZAWA , F., PROPERZI, M.; PICHELIN, F. (2004): Wood dowel bonding by high-speed rotation welding. J. Adhesion Sci. Technol., 18 (11): pp. 1263-1278.

RIVER, B. H.; OKKONEN, E. A. (1991): Delamination of Edge-Glued Wood Panels: Moisture Effects. Limited number of free copies. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest products Laboratory.

ROWELL, R. M.; LEVAN-GREEN, S. L. (2005): Thermal Properties in: Handbook of Wood Chemistry and Wood Composites, CRC Press, Boca Raton, FL, pp. 121-138.

SHAFIZADEX , F. (1963): Acidic hydrolysis of glycoside bonds. Tappi, (46): 381-383. ŽUPČIĆ, I. (2010): Čimbenici koji utječu na spajanje tokarenih bukovih elemenata tehnikom

zavarivanja. Disertacija, Sveučilište u Zagrebu, Šumarski fakultet, pp. 1-237. ŽUPČIĆ, I.; BOGNER, A.; GRBAC, I.; LOZANČIĆ, I. (2010): New insights into rotation welding of beech

wood. International Conference, Wood is good – transfer of knowledge in practice as a way out of the crisis. Innovawood, University of Zagreb, Faculty of Forestry, Croatia 15th October, pp. 147-152.

ŽUPČIĆ, I.; BOGNER, A.; GRBAC, I. (2011): Vrijeme trajanja zavarivanja kao važan čimbenik zavarivanja bukovine. Drvna industrija, 62 (2): pp. 115-121.

HRN ISO 3130 (1999): hrvatska norma za određivanje sadržaja vode za ispitivanje fizikalnih i mehaničkih svojstava drva.

HRN ISO 3131 (1999): hrvatska norma za određivanje gustoće drva za ispitivanje fizikalnih i mehaničkih svojstava drva.


175

The Effects of Press Time and Press Pressure on Modulus of Rupture and Modulus of Elasticity Properties of Oriented Strength Board (OSB)

Manufactured from Poplar Wood

YAPICI Fatiha*– ESEN Raşitb a Karabük University-Forestry Faculty-Department of Forest Industry Engineering Karabuk and Turkey

b Karabük University-Technical Education Faculty-Department of Furniture and Decoration Education Karabuk and Turkey

*Corresponding author: [email protected] Abstract – This study was carried out to determine the effects of pres time and pres pressure on modulus of rupture (MOR) and modulus of elasticity (MOE) properties of oriented strand board (OSB). For this purpose, 80 mm long strands made of poplar wood bonded with phenol-formaldehyde resin at (9 %) with three-layer cross-aligned OSBs. The strands used for the production of test panels were made up 50 % of core layer and 50 % of outer layers. The panels were pressed for three different press times, from 3, 6 to 9 minutes, using 30, 40 and 50 kg/cm2 bar pressure respectively, aimed for density of 0.65 g/cm3.

oriented strand board / phenol-formaldehyde / MOR value / MOE value 1. INTRODUCTION

The decline of a high quality wood supply has led to an increased demand for wood composite materials over the past forty years. The major advantage of wood composite materials which are manufactured from unnused low quality wood and residues of other wood sectors. The wood composite materials which are included panel products such as plywood, particleboard, medium-density fiberboard, and oriented strandboard (OSB) (HU, 2000). Oriented Strand Board (OSB) is an engineered structural wood panel. OSB is made by processing small diameter, fast growing trees into thin strands which are bonded together under heat and pressure with an exterior resin binder. OSB panels are used various applications such as building construction, furniture, roofing and flooring (YAPICI et al., 2009)

Some mechanical properties of OSB panels are equal the playwood panels used for structure areas and the process of manufacturing OSB is comparatively cheaper than plywood industrial, too. (BROCHMANN et al., 2004). OSB industry was developed by using low-density hardwoods such as aspen, yellow-poplar, southern pine, lodge pole pine, jack pine, scotch pine, and so on (MALONEY, 1996). Because of this, there are many studies in the literature related to OSB panels.

Pressing operation is an extremely critical step in the OSB manufacturing process. Pressing conditions depend on resin type and amount, board density; furnish moisture content and thickness of the panels (BAŞTÜRK, 1999). HSU AND KRINCIC (1997) stated that the internal bond and wet modulus of rupture were substantially increased, and the thickness swelling was reduced as the platen temperature was increased from 223 °C to 232 °C.

The mechanical and physical properties of OSB panels are affected by many factors such as raw materials type, adhesive type and ratio, press time and pressure. The most important parameters affecting the properties of OSB are press pressure and press time. The determination of effects of these factors on the physical and mechanical properties of panels is very important for the manufacturing of OSBs. In this study, the aim is to evaluate the effects of press time and press pressure on modulus of rupture and modulus of elasticity of OSB.


176


The poplar wood was used in the production of the (OSB). The strands dimension in usage was approximately 80 mm long, 20 mm wide and 0.7 mm thick. Firstly, the wood strands were dried until 3 % moisture content before adhesive was sprayed on them for three minutes. Then, the adhesive material within 47 % liquid phenol- formaldehyde resin, was applied in 9 percent ratios based on the weight of oven dry wood strands.

The press periods and press pressure were 3, 6 and 9 minutes under the 30-40 and 50 kg/cm2 press pressure, respectively. The shelling ratio was 50 % for core layer and 50 % for face layer, and density of the boards was aimed at 0.67 g/cm3 density. OSB panels, which were dimensioned as 56x56x1.2 cm were made for experiments, in the nine conditions. They were 18 in total as two for each. Hand formed mats were pressed in a hydraulic press. These panels were labeled from 1 to 6. All mats were pressed under automatically controlled conditions at 195±2 ºC. After pressing, the boards were conditioned to constant weight at 65±5 % relative humidity and at a temperature of 20±2 ºC until they reached stable weight (TS 642 1997). The density, moisture content, modulus of rupture and modulus of elasticity values of OSBs were determined according to the related standards (TS-EN 323 1999; TS-EN 322 1999; TS EN 310 1999).

During the measurement of screw strength values were determined using Zwick/Roell Z050 universal test device with capacity of 5000 kg and measurement capability of 0.01 Newton in accuracy. In testing, loading mechanism was operated with a velocity of 10 mm/min.

Data for each test was statistically analyzed. The analysis of variance (ANOVA) was used (α<0.05) for testing significant difference between factors. When the ANOVA indicated a significant difference among factors, the compared values were evaluated with the Duncan test to identify which groups were significantly different from other groups.

3. RESULT, DISCUSSION AND CONCLUSION The density (D) and moisture content (MC) values of OSBs were determined according

to the related standards. The average density and moisture content of panels were obtained as 0.67 g/cm3 and 7.4 %, respectively. It was seen that the aimed and acquired density and moisture content values within the ranges as specified in the related standards. The average and standard deviation of the values of the modulus of rupture and modulus of elasticity of produced panels are shown in Table 1.

Table 1. Summary of the test results of the OSBs

MOE (N/mm2) MOR(N/mm2) Press Pressure Press Time Mean Std. Dev. Mean Std. Dev.

30 3 5973.81 352.40 27.35 2.56 6 6206.97 982.73 47.17 3.49 9 6280.95 216.64 45.08 2.60

40 3 5193.86 513.60 20.71 2.15 6 6791.21 688.11 38.50 1.46 9 5345.78 1170 36.11 1.21

50 3 6629.10 397.62 33.47 3.11 6 2980.22 481.50 35.96 4.80 9 2950.18 581.00 31.10 4.02

It was found that the MOR and MOE values of the test panels varied between 20.71 –

47.17 N/mm2 and 2950.18-6791.21 N/mm2, respectively. The lowest value for MOR of


177

produced panels was 20.71 N/mm2 (40 kg/cm2 and 3 minutes press time). The variance analysis of MOR and MOE based on manufacturing circumstances of test panels was done by using one-way variance analysis (Table 2). Table 2. The result of variance analysis

Source

Type III Sum of Squares

Df Mean Square F Value Sig.

(p<0.5)

MOE (N/mm2)

Corrected Model 85491126.81 8 10686390.85 24.22 0.00 Intercept 1298849045.63 1 1298849045.63 2944.06 0.00 Pressure 32711660.76 2 16355830.38 37.07 0.00 Time 8687820.35 2 4343910.18 9.85 0.00 Pressure*Time 44091645.69 4 11022911.42 24.99 0.00 Error 15882349.99 36 441176.39

Total 1400222522.42 45

MOR (N/mm2)

Corrected Model 2721.349 8 340.17 36.93 0.00 Intercept 55295.93 1 55295.93 6003.17 0.00 Pressure 544.92 2 272.46 29.58 0.00 Time 1466.77 2 733.38 79.62 0.00 Pressure*Time 709.66 4 177.42 19.26 0.00 Error 331.60 36 9.21

Total 58348.88 45

According to the variance analysis, the effects of the both press time and press pressure

on the modulus of elasticity values were significant statistically. Duncan test results conducted to determine the importance of the differences between the groups are given in Table 3.


MOE MOR

Mean HG Mean HG

Press Pressure 50 4186.50 A 33.51 A 40 5776.95 B 31.77 A 30 6153.91 B 39.87 B

Press Time 9 4858.97 A 37.43 B 6 5326.14 A 40.54 BC 3 5932.26 B 27.18 A

It can be seen that the changed of MOE values were changed from 4186.50 N/mm2 to

6153.91 N/mm2 according to Duncan's test, they were also given the same and different homogenous groups. In addition, MOR values were changed between 27.18 N/mm2 and 40.54 N/mm2, and they were given same and different homogenous groups.

In this study, effects of press pressure and press time which are very important factors on the modulus of rupture (MOR) and modulus of elasticity (MOE). MOR and MOE values were affected by changing these factors. It can stated that as the press time increased, the values of modulus of rupture improved and without any impact on modulus of elasticity. But, It was seen that as press pressure increased, the values of MOR and MOE decreased. It can said that these values were decreased due to degrade of individual strand produced from poplar wood that have low density properties by increasing press pressure.


178

4. REFERENCES BROCHMANN, J.; EDWARDSON, C.; SHMULSKY , R. (2004): Influence Of Resin Type And Flake

Thickness On Properties Of OSB. Forest Prod. J. 54 (3):51–5. MALONEY, T.M. (1996) :The family of wood composite materials. Forest Prod. J. 46 (2): pp. 19-26. BASTÜRK, M.A. (1999): Improvements of The Oriented Strand Board With Chitosan Treatments of

The Strands. Ph.D. Thesis, Syracuse, New York, USA. HSU, W.E.; KIRINCIC, S. (1997): OSB Quality Enhancement And Cost Reduction. Proceedings

International Particleboard/Composite Material Symposium. W.S.U.: pp. 91-99. PAO-JEN, (STEVE) H. (2000): Bending Stiffness Prediction For Oriented Strandboard By Classıcal

Laminatıon Theory. University Of Toronto, 1-2. TS 642/ISO 554 (1997): Standard Atmospheres And /Or Testing; Specifications TS-EN 323 (1999): Wood-Based Panels,-Determination Of Density, TSE, Ankara. TS-EN 322 (1999): Wood-Based Panels,-Determination Of Moisture Content, TSE, Ankara TS EN 310 (1999): Wood-Based Panels-Determination Of Modulus Of Elasticity And Of Bending

Strength, TSE, Ankara. YAPICI, F.; GÜNDÜZ, G.; ÖZÇIFÇI, A.; LIKOS, E. (2009): Prediction of Screw and Nail Withdrawal

Strength on OSB (Oriented Strand Board) Panels With Fuzzy Classifier, Technology, 12 (3): pp. 167-174.


179

The Effects of Cast-Polyamide on the Modulus of Rupture and Modulus Elasticity of Oriented Strength Board (OSB) Manufactured

from Scotch Pine

YORUR Huseyina*– YAPICI Fatiha – ESEN Rasitb

a Department of Forest Industry Engineering, Forestry Faculty, Karabuk University, Karabuk, Turkey. b Department of Furniture and Decoration Education, Technical Education Faculty, Karabuk University,

Karabuk, Turkey. *Corresponding author: [email protected]

Abstract – This study was carried out to determine the effects of using cast-polyamide on modulus of rupture (MOR) and modulus elasticity (MOE) of oriented strand board (OSB) which were produced in four different conditions. Firstly, control panels were manufactured, and also OSB panels produced by adding cast-polyamide with 20 % - 30 % ratio compare with weight of oven dry wood particle both out layer and inner layer. Phenol formaldehyde was used at 6 % ratio. Strands were used to the production of panels made up 50 % of core layer and 50 % of outer layers. Test panels were pressed in 6 min., 40 kg/cm2 press pressure and 185±3 °C press temperature by aiming for a target density of 0.67 g/cm3. The values of modulus of rupture and modulus elasticity were determined by using according to related standard.

oriented Strand Board /MOR value / MOE value / cast-polyamide/ phenol-formaldehyde 1. INTRODUCTION

The major advantage of wood composite materials is that they can be manufactured from unused low quality wood and residues of other wood sectors. The wood composite materials are plywood, particleboard, medium-density fibreboard, and oriented strandboard (OSB) (HU, 2000).

ZHU et al. (2005) stated that OSB is made of thin strands of wood mainly from commercially grown trees. The unsurpassed orientation of the flakes gives it relatively higher mechanical properties in the direction of the flakes than in the transverse direction (ZHU et al., 2005). OSB is an engineered wood product that is manufactured from wood particles known as strands, after bonded together with waterproof resin under pressure and heat (BASTÜRK, 1999).

OSB panels are widely used in many applications of the wood construction industry. One of the advantages of OSB is its equivalent mechanical properties and substantially lower cost compared to structural ply wood (HOWARD, 2000). Low-density hardwoods such as aspen, yellow-poplar, southern pine, lodge pole pine, jack pine, scots pine were used in the beginning state of OSB industry (MALONEY, 1996). YAPICI (2008) stated that while increase of adhesive ratio and press time, improve of modulus of rupture and modulus elasticity values of OSB panels produced in three different adhesive ratio (3-4, 5-6 %), three different press time (3-5 and 7 min.) and three different press pressure (35-40 and 45 kg/cm2).

In this study, the aim is to evaluate the effects of using cast-polyamide on modulus of rupture and modulus of elasticity of OSB panels.


Scots Pine wood (Pinus sylvestris L.) was used in the production of the (OSB). The strands dimension in usage was approximately 80 mm long, 20 mm wide and 0.7 mm thick.


180

First, the wood strands were dried to 3 % moisture content before adhesive was sprayed on them for three minutes. The press conditions were applied on 6 minute press time under the 40 kg/cm2 press pressure, respectively. The shelling ratio was 50 % for core layer and 50 % for face layer, and density of the boards was aimed at 670 kg/m3 density. OSB panels, which were dimensioned as 56x56x1.2 cm, were made for experiments.

Totally, five OSB panels were produced such as control panels which were done by using cast-polyamide and other panels. Control panels were made by applying adhesive material without wax, a solid content of 47 % liquid phenol- formaldehyde resin, was applied in 6 % ratios based on the weight of oven dry wood strands. The other panels was produced by adding cast-polyamide with 20 % - 30 % ratio compared to weight of oven dry wood particle both in outer layer and inner layer.

There were 10 in total as two for each group. Hand formed mats were pressed in a hydraulic press. These panels were labelled from 1 to 5. All mats of panels were pressed under automatically controlled conditions at 185±2 ºC. After pressing, the boards were conditioned to constant weight at 65±5 % relative humidity and at a temperature of 20±2 ºC until they reached stable weight (TS 642 1997). The density, moisture content, modulus of rupture and modulus of elasticity values of OSBs were determined according to the related standards (TS-EN 323 1999; TS-EN 322 1999; TS EN 310 1999).

Measurements of MOR and MOE values were determined using Zwick/Roell Z050 universal test device with capacity of 5000 kg and measurement capability of 0.01 N of accuracy. In testing, loading mechanism was operated with a velocity of 6 mm/min.

Data for each test were statistically analysed. The analysis of simple variance analysis was used (α<0.05) to test for significant differences between factors. When the ANOVA indicated a significant difference among factors, the compared values were evaluated with the Duncan test to identify which groups were significantly different from other groups.

3. RESULTS AND DISCUSSIONS

The density and moisture content values of OSBs were determined according to the related standards. The average density and moisture content of panels were obtained as 670 kg/m3 and 6.9 %, respectively. The average and standard deviation values of the modulus of rupture and modulus of elasticity of produced panels are shown in the Table 1.

Table 1. MOR and MOE values

Experimental conditions MOR (N/mm2) MOE (N/mm2)

Mean Standard

Dev. Mean

Standard Dev.

0 (Control- non cast polyamide) 21.93 4.02 4277.08 800.95 1 (Cast polyamide only core layers with 30 %) 25.50 2.86 4225.32 1432.19 2 (Cast polyamide only outer layers with 30 %) 19.82 2.22 3331.52 939.25 3 (Cast polyamide only core layers with 20 %) 25.31 4.11 4934.93 1062.86 4 (Cast polyamide only outer layers with 20 %) 26.39 6.53 4940.61 969.88

MOR and MOE values were two of the most common tests in the OSBs. It was found

that the MOR and MOE values of the test panels varied between 19.82 – 26.39 N/mm2 and 3331.52 – 4940.61 N/mm2, respectively. The variance analysis of MOR and MOE based on manufacturing conditions of test panels was done by using one-way variance analysis (Table 2).


181

Table 2. The result of variance analysis

Sum of Squares Df Mean Square F- Value Sig.level 186.77 4 46.69 2.62 0.05 445.02 25 17.80

631.80 29

According to the variance analysis, the effects of the cast-polyamide on the modulus of elasticity values and modulus of rupture values were not statistically significant. Duncan test results are given in Table 3.


Experiment conditions Mean HG

MOR values

2- Cast polyamide only outer layers with 30 % 19.82 A 0- Control- non cast polyamide 21.96 AB

3- Cast polyamide only core layers with 20 % 25.31 B 1- Cast polyamide only core layers with 30 % 25.50 B 4- Cast polyamide only outer layers with 20 % 26.39 B

MOE values

2- Cast polyamide only core layers with 30 % 3331.52 A 1- Control- non cast polyamide 4225.32 AB

0- Cast polyamide only outer layers with 30 % 4277.08 AB 3- Cast polyamide only core layers with 20 % 4934.93 B 4- Cast polyamide only outer layers with 20 % 4940.61 B

It can be seen that the MOR values changed between 19.82 N/mm2 and 26.39 N/mm2

according to Duncan's test. panels number 1.3 and 5 was given the same homogenous groups. In addition, MOE values changed between 3331.52 N/mm2 and 4940.61 N/mm2, and they were put in the different homogenous groups.

4. CONCLUSION

In this study, the values of MOR and MOE were among the most important mechanical features of oriented strand boards. Especially, it can be stated that if used cast-polyamide ratio was increased, the modulus of rupture values of test panels improved on the test panels produced by using cast-polyamide in core layer with 30 % and 20 %. The highest MOR value was obtained from fourth samples as 26.39 N/mm2, the lowest values of this were obtained from second samples as 19.82 N/mm2. Also, the results showed that the values of modulus of elasticity changed between 3331.52 and 4940.61 N/mm2. 5. REFERENCES BASTÜRK, M.A. (1999): Improvements of the Oriented Strand Board With Chitosan Treatments of

The Strands. Doctoral thesis, Syracuse, New York, USA. HOWARD, J.L. (2000): U.S. Forest Products Annual Market Review and Prospects. FPL-RN-0278.

USDA Forest Serv., Forest Prod. Lab., Madison, WI. MALONEY, T.M. (1996): The family of wood composite materials. Forest Prod. J. 46 (2): pp.19-26. PAO-JEN, (Steve) H. (2000): Bending stiffness prediction for oriented strandboard by classıcal

laminatıon theory, University of Toronto, 1-2. YAPICI, F. (2008): The effect of some production factors on the properties of OSB made from scots

pine (Pinus sylvestris L.) wood. Zonguldak Karaelmas University, Bartın, Turkey.


182

ZHU, E.C.; GUAN, Z.W.; RODD, P.D.; POPE, D.J. (2005): Finite element modelling of OSB webbed timber I-beams with interactions between openings. Advances in Engineering Software 36, pp.797–805.

TS 642/ISO 554 (1997): Standard atmospheres and /or testing; Specifications TS-EN 323 (1999): Wood-Based panels,-Determination of density, TSE, Ankara. TS-EN 322 (1999): Wood-Based panels,-Determination of moisture content, TSE, Ankara TS EN 310 (1999): Wood-Based panels-Determination of modulus of elasticity and of bending strength, TSE, Ankara.

October 18th

2013

ZAGREBCROATIA

Documents

wood is good - user oriented material, technology and design