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Towards Sustainability Using
Minimum Quantity Lubrication
Technique and Nano-Cutting Fluids
in Metal-Machining Processes.
Author: Marta García Tierno
Publication type: Master thesis
Supervisor: Amir Rashid
University: KTH Royal Institute of Technology, Stockholm, Sweden
Department: Department of Production Engineering
Marta García I
ACKNOWLEDGEMENTS
First, I would like to thank professor Amir Rashid, for giving me this opportunity and for his
support. Also, I would like to thank Javier Echavarri, for supervising my thesis from Spain, thanks
for all your comments and corrections given.
Secondly, I want to express my gratitude to LetsNano AB team. Professor Muhammet Toprak,
Bernhard Hirschauer, Tafazzul Mahmood and Nader Nikkam. This project and my work at KTH
couldn’t be possible without their effort and support. I would also like to thank to the people
working at the laboratory at IIP-KTH, specially Anton Kviberg, Jan Stamer and Mats Bejhem for
sharing with me his endless knowledge and wisdom.
Finally, I would like to mention my family, always supporting me in all the aspects of my life,
specially my father and my aunt, Pascual and Rosa. And to my friends, both the ones living in Spain
and the ones in Stockholm, for helping me every day and making me happy.
For those of you who helped me directly or indirectly and I may have forgotten, many thanks.
Marta García II
ABSTRACT
Sustainable manufacturing is making products from processes which have minimal environmental
impact, energy and resource efficient, economically viable and safe for consumers and society as
whole. Achieving sustainability in manufacturing would mean infusing sustainability methods on
product process and system level. On the process level, machining technology is one of the most
widely extended processes in the industry. One way to attain sustainability in this technology is by
adopting efficient management of Metal Working Fluids (MWF). In this purpose to reduce the
amount of MWF starts Minimum Quantity Lubrication (MQL), where very small quantity of fluid
is applied to the cutting zone with maximum precision. Moreover, addition of nanoparticles to
these ´minimum quantity lubricants´ further enhances its tribological properties leading to higher
reduction in friction and temperature in the machining process.
The main objective of this thesis is to study the performance of cooling-lubricating fluids and these
fluids modified with nanoparticles, how the use of this new lubricants improves the results obtained
in material process technologies, particularly in turning. This project is being supported by the
company LetsNano AB, providing the lubricants enhanced with nanoparticles and the funding,
and Accu-Svenska AB, providing base oil and MQL technology.
The experiments are carried out at Kungliga Tekniska Högskolan (KTH), at Institutionen för
Industriell Produktion (IIP) laboratory. The turning process was tested with two different
workipiece materials: hardened steel (Toolox® 44) provided by SSAB, and grey cast iron (Scania
case study material). Two different tooling systems, due to the different materials. One provided
by Mircona AB, and the other given directly by Scania, provided by Sandvik AB and Cermatec AB.
The MQL system is a high-performance booster provided by Acuu-Svenska AB. The lubricant is
a vegetable oil that will also be the base for the Nanofluids (NF). This Nanofluids and produced
and developed by LetsNanoAB.
The study revealed an encouraging potential of moving from conventional (dry) cooling techniques
to the vegetable oil based MQL. Machining performance of MQL was encouraging as in most of
the cases the systematic reduction in tool wear reveals a better machinability. The contribution of
this work for Scania could help them to take the decision and move to more sustainable machining
processes. To prove the potential of the nanotechnology in this kind of processes further study is
needed, and it is going to be tested at IIP facilities in near future. The implementation of this
technology brings more challenges that should considered a study of the hazards of the technology
(emissions, fire and explosion, noise, skin…) necessary safety measures (cleaning, operator
instruction, skin protection…) and modifications in the machine tools system beyond the process
only. This could also be a next step in the further study of this research.
Keywords: Manufacturing, Machining, Turning, Minimum Quantity Lubrication, Nanoparticles.
UNESCO Codes: 3316.07; 2210.30.
Marta García III
SAMMANFATTNING
Hållbar tillverkning gör produkter från processer som har minimal miljöpåverkan, energi och
resurseffektiv, ekonomiskt genomförbar och säker för konsumenterna och samhället som helhet.
Att uppnå hållbarhet i tillverkningen skulle innebära infusion av hållbarhetsmetoder på
produktprocess och systemnivå. På processnivå är bearbetningsteknologi en av de mest utbredda
processerna inom branschen. Ett sätt att uppnå hållbarhet i denna teknik är genom att anta effektiv
hantering av metallbearbetningsvätsko (MWF). I detta syfte för att minska mängden MWF startas
Minimalsmörjning (MQL), där mycket liten mängd vätska appliceras på skärzonen med maximal
precision. Dessutom ökar tillsatsen av nanopartiklar till dessa "minimala smörjmedel" ytterligare
sina tribologiska egenskaper vilket leder till högre minskning av friktion och temperatur i
bearbetningsprocessen.
Huvudsyftet med denna avhandling är att studera prestanda av kylsmörjande vätskor och dessa
vätskor modifierade med nanopartiklar, hur användningen av de här nya smörjmedlen förbättrar
resultaten som erhållits i materialteknik, särskilt vid vridning. Projektet stöds av företaget LetsNano
AB, vilket ger smörjmedlen förbättrad med nanopartiklar och finansieringen, och Accu-Svenska
AB, som erbjuder basolja och MQL-teknik.
Experimenten utförs vid Kungliga Tekniska Högskolan (KTH) vid Institutionen för Industriell
Produktion (IIP). Vridprocessen testades med två olika material: Härdat stål (Toolox® 44) som
SSAB levererade och grått gjutjärn (Scanias fallstudiematerial). Två olika verktygssystem, på grund
av olika material. En som tillhandahålls av Mircona AB och den andra som ges direkt av Scania,
tillhandahållen av Sandvik AB och Cermatec AB. MQL-systemet är en högpresterande booster
som tillhandahålls av Acuu-Svenska AB. Smörjmedlet är en vegetabilisk olja som också kommer
att vara basen för Nanofluiderna (NF). Dessa Nanofluider och produceras och utvecklas av
LetsNanoAB.
Studien avslöjade en uppmuntrande potential att flytta från konventionell (torr) kylningsteknik till
den vegetabiliska oljebaserade MQL. Maskinens bearbetningsförmåga var uppmuntrande,
eftersom i de flesta fallen den systematiska minskningen av verktygsslitaget visar bättre bearbetning.
Arbetet med detta arbete för Scania kan hjälpa dem att fatta beslut och flytta till mer hållbara
bearbetningsprocesser. För att bevisa nanoteknikens potential i denna typ av processer krävs
ytterligare studier, och det kommer att bli testat vid IIP-anläggningar inom en snar framtid.
Genomförandet av denna teknik ger fler utmaningar som bör övervägas en studie av farorna med
tekniken (utsläpp, brand och explosion, buller, hud ...) nödvändiga säkerhetsåtgärder (rengöring,
operatörsinstruktion, skydd mot huden ...) och modifikationer i verktygsmaskinerna system utöver
processen bara. Detta kan också vara nästa steg i den fortsatta studien av denna forskning.
Marta García IV
TABLE OF CONTENTS
LIST OF FIGURES .................................................................................................................................................. VI
LIST OF TABLES ..................................................................................................................................................... IX
LIST OF ABBREVIATIONS ................................................................................................................................. XI
LIST OF NOMENCLATURE ............................................................................................................................. XII
1 INTRODUCTION ............................................................................................................................................1
1.1 Background ................................................................................................................................................1
1.2 Objectives ...................................................................................................................................................2
1.3 Thesis structure ..........................................................................................................................................3
1.4 Collaborators ..............................................................................................................................................4
1.4.1 LetsNano AB ........................................................................................................................................4
1.4.2 Accu-Svenska AB .................................................................................................................................4
1.4.3 Scania: Case study .................................................................................................................................5
1.5 Time planning ............................................................................................................................................6
2 STATE OF THE ART ......................................................................................................................................8
2.1 Sustainable manufacturing in machining ...............................................................................................8
2.2 Tribology of metal cutting .......................................................................................................................9
2.3 Minimum Quantity Lubrication Technique (MQL) ......................................................................... 12
2.3.1 Characteristics .................................................................................................................................... 13
2.3.2 Advantages ......................................................................................................................................... 15
2.3.3 Heat management in MQL .............................................................................................................. 17
2.4 Minimum Quantity Lubrication (MQL) using Nano-cutting Cooling Fluids .............................. 18
2.5 Previous work at KTH-IIP ................................................................................................................... 27
3 EXPERIMENTAL METHODOLOGY .................................................................................................... 28
3.1 Planning of the experiments ................................................................................................................. 28
3.2 Experimental set-up ............................................................................................................................... 29
3.2.1 CNC turning-lathe machine ............................................................................................................. 29
Marta García V
3.2.2 Workpiece material ............................................................................................................................ 31
3.2.3 Tooling system ................................................................................................................................... 34
3.3 Description of the MQL system .......................................................................................................... 38
3.4 Collection of the machining variables ................................................................................................. 40
3.4.1 Measurement of tool wear mechanisms and tool life .................................................................. 40
3.4.2 Measurement of Temperature in the cutting zone ....................................................................... 44
3.4.3 Measurement of the Surface Roughness ....................................................................................... 45
4 RESULTS AND DISCUSSION: TOOLOX® 44 ...................................................................................... 49
4.1 Preliminary results .................................................................................................................................. 49
4.2 Comparison between different lubrication techniques .................................................................... 51
4.2.1 1 mm of depth of cut ........................................................................................................................ 51
4.2.2 0.5 mm of depth of cut ..................................................................................................................... 57
5 RESULTS AND DISCUSSION: SCANIA CASE STUDY .................................................................... 60
5.1 Comparison between different lubrication techniques .................................................................... 61
5.1.1 Tool wear and tool life ..................................................................................................................... 61
5.1.2 Surface roughness .............................................................................................................................. 65
5.1.3 Temperature ....................................................................................................................................... 67
6 CONCLUSIONS AND FUTURE WORK ................................................................................................ 69
6.1 Recommendations for future work ..................................................................................................... 70
REFERENCES .......................................................................................................................................................... 71
APPENDIX A. CODES .......................................................................................................................................... 76
APPENDIX B. FLANK WEAR EVOLUTION ................................................................................................ 82
APPENDIX C. SURFACE ROUGHNESS MEASUREMENTS ................................................................... 85
APPENDIX D. POSTER PVC ANNUAL CONFERENCE .......................................................................... 86
Marta García VI
LIST OF FIGURES
Figure 1. Structure of the master thesis. .................................................................................................. 3
Figure 2. LetsNano AB [3]. ........................................................................................................................ 4
Figure 3. Accu-Svenska AB [4].................................................................................................................. 4
Figure 4. Scania AB [6]. .............................................................................................................................. 5
Figure 5. Gantt diagram of the master thesis. ......................................................................................... 7
Figure 6. Basic elements of sustainable machining [8]. .......................................................................... 8
Figure 7. Cutting process as a tribological system [10]. ....................................................................... 10
Figure 8. Flood cooling with Emulsion [15]. ........................................................................................ 12
Figure 9. Minimum Quantity Lubrication System (MQL) [17]. ......................................................... 13
Figure 10. Metal working fluid costs in metal machining [20]. ........................................................... 15
Figure 11. Percentage of energy consumption in wet machining [18]. ............................................. 16
Figure 12. Comparison of emission during machining between wet and MQL turning [22]. ....... 16
Figure 13. Heat generation in metal cutting [19]. ................................................................................. 17
Figure 14. Possible lubrication mechanisms by the application of Nano-oil between the frictional
surface [25]. ................................................................................................................................................. 18
Figure 15. Variation of flank wear and nodal temperature with machining time [27]. ................... 19
Figure 16. Flank wear vs. machining time 4 cooling techniques and two Nanofluids 1. Al2O3
and 2. TiO2[30, 31]. ................................................................................................................................... 20
Figure 18. Specific energy and power reduction for both lubrication mode [35]. ........................... 21
Figure 17. Variation of surface roughness with cutting condition [34]. ............................................ 21
Figure 19. Tool wear vs. number of cuts [2]. ........................................................................................ 27
Figure 20. Schemetic and picture SMT Swedturn 300 [41]. ................................................................ 29
Figure 21. Schematic diagram of turning operation and cutting parameters [43]. ........................... 30
Figure 22. Workpiece material groups [44]............................................................................................ 31
Figure 23. Cemented carbide inserts, DCMT 11 T3 08-PM7. ........................................................... 34
Marta García VII
Figure 24. Tool holder design for MQL, Mircona AB [8]. ................................................................. 35
Figure 25. Tool holder for MQL, Mircona AB. ................................................................................... 35
Figure 26. Oxide ceramic inserts, DNMX 15 T07 12. ......................................................................... 36
Figure 27. MQL external supplier designed at KTH-IIP. ................................................................... 37
Figure 28. Clamping system for Scania Set-up...................................................................................... 37
Figure 29. Ecolubric MQL booster and Ecolubric E200L vegetable oil. ......................................... 38
Figure 30. MQL booster drawing and components list. ..................................................................... 39
Figure 31. Microscope NIKON Optiphot 150. .................................................................................. 40
Figure 32. DeltaPix Insigtht software..................................................................................................... 40
Figure 33. Types of tool wear (a. Flank wear, b. Crater wear, c. Built-up edge, d. Notch wear, e.
Plastic deformation, f. Thermal cracks, g. Edge breakage) [55]. ......................................................... 42
Figure 34. Cutting profile for grey cast iron machining experiments. ............................................... 43
Figure 35. Thermal infrared camera FLIR SC 640 [55]. ...................................................................... 44
Figure 36. ThermaCAM Researcher Professional 2.10. Software. ..................................................... 45
Figure 37. Mitutoyo SJ-210 Surface Roughness Tester. ...................................................................... 46
Figure 38. Surface roughness profile and values, Ra, Rz and Rq for JIS 2001 standard [57] ........ 47
Figure 39. Effect of geometric factors in determining the theoretical finish on a work surface for
single-point tools: (a) effect of nose radius, (b) effect of feed, and (c) effect of end cutting-edge
angle [57]. ..................................................................................................................................................... 48
Figure 40. Flank wear vs. Machining time, first experiments Toolox® 44, dry machining. ........... 50
Figure 41. Flank wear vs. Machining time, first unsuccessful experiments Toolox® 44, three
lubrication techniques. ............................................................................................................................... 50
Figure 42. Damaged and broken chip breaker, crater images x10, 1mm of depth of cut, dry
machining. ................................................................................................................................................... 51
Figure 43. Crater images x10, 0,5 mm of depth of cut. ....................................................................... 52
Figure 44. Flank wear vs. machining time for dry and MQL, 1 mm of depth of cut, Toolox 44. 52
Figure 45. Comparison of tool life, dry and MQL, 1 mm of depth of cut, Toolox 44. ................. 53
Marta García VIII
Figure 46. Flank wear measurement, 1 mm of depth of cut, dry,MQL with vegetable oil and
compressed air. ........................................................................................................................................... 53
Figure 47. Flank and Crater images x10, 13,3 mins of machining, 1 mm, Toolox 44 (a)Dry
machining (b)Compressed air (c)MQL. .................................................................................................. 54
Figure 48. Temperature graphs 1 mm, dry, air and MQL, Toolox 44(a)Average temperature vs.
machining time (b)Evolution of T during 90 s of machining (c) Evolution of T last 15 s of one
machining step. ........................................................................................................................................... 55
Figure 49. Instantaneous Temperatures IR image, compressed air, 1 mm, Toolox 44. ................. 56
Figure 50. Chips samples for Dry, Compressed air and MQL, 0.5 mm, Toolox 44. ...................... 57
Figure 51. Flank wear vs. machining time for dry, air and MQL, 0.5 mm of depth of cut, Toolox
44. ................................................................................................................................................................. 58
Figure 52. Flank images, 15 mins of machining, 0.5mm of depth of cut, Toolox 44. .................... 58
Figure 53. Average temperature vs. machining time, 0,5 and 1 mm, Toolox 44. ............................ 59
Figure 54. Flank and crater images x5, new ceramic insert. ................................................................ 61
Figure 55. Flank and crater images x5, broken ceramic inserts, Scania sample. .............................. 61
Figure 56. Orientation of nozzles, Scania case study tool holder. ..................................................... 63
Figure 57. Flank wear vs. N of test specimen, Dry 1, MQL 1 and MQL 2 Scania case study. ..... 63
Figure 58. Flank wear vs. N of test specimen, three techniques, Scania case study. ....................... 64
Figure 59. Flank wear images at the end of tool life Dry 1 x10, NF 2 x5, MQL 3 x10, Scania case
study. ............................................................................................................................................................ 64
Figure 60. Comparison of tool life, three cooling techniques, Scania case study. ........................... 65
Figure 61. Average arithmetical mean surface roughness Ra (µm), Scania case study. ................... 65
Figure 62. Surface roughness profile 1. Scania test specimen sample, 2. MQL + NF, 3. MQL +
Vegetable oil, 4. Dry machining. .............................................................................................................. 66
Figure 63. Scania set-up image. ............................................................................................................... 67
Figure 64. Temperature in the cutting zone vs. machining time, Scania case study. ...................... 67
Figure 65. Instantaneous Temperature IR image, Scania case study. ................................................ 68
Figure 67. Flank wear vs. machining time, 0.5 mm Toolox 44. ......................................................... 84
Figure 68. Flank images, evolution of tool wear................................................................................... 84
Marta García IX
LIST OF TABLES
Table 1. Work packages decomposition. .................................................................................................. 6
Table 2. Lubrication strategies and its functions [10]. .......................................................................... 10
Table 3. Summary of MQL with NF with different nanoparticles literature for turning process. . 23
Table 4. Summary of MQL with NF with different nanoparticles literature for milling process. . 25
Table 5. General technical data SMT Swedturn 300 [41]. .................................................................... 29
Table 6. Turning parameters. .................................................................................................................... 30
Table 7. Chemical composition Toolox 44 [46]..................................................................................... 32
Table 8. Mechanical and phyical properties of Toolox® 44 [46]. ....................................................... 32
Table 9. Chemical composition of grey cast iron. ................................................................................. 33
Table 10. Hardness and microstructure of grey cast iron..................................................................... 33
Table 11. Geometrical properties of the carbide inserts. ..................................................................... 34
Table 12. Benefits of insert coatings [54]. ............................................................................................... 35
Table 13. Geometrical properties of the ceramic inserts. ..................................................................... 36
Table 14. General properties of Ecolubric E200L [11]. ....................................................................... 38
Table 15. Test specimen equivalent cutting parameters. ...................................................................... 43
Table 16. General specification on thermal infrared camera FLIR SC 640 [12]. .............................. 44
Table 17. Specifications of Surface Roughness Tester Mitutoyo SJ-210 [56]. .................................. 45
Table 18. Surface roughness JIS 2001 standard parameters. ............................................................... 46
Table 19. Cutting parameters, first experiments Toolox® 44. ............................................................. 49
Table 20. Cutting parameters, Toolox 44 experiments. ........................................................................ 51
Table 21. Tool life, dry and MQL, 1 mm, Toolox 44. .......................................................................... 53
Table 22. Average temperature values, 0,5 and 1 mm, Toolox 44. ..................................................... 59
Table 23. Cutting parameters, Scania Case Study. ................................................................................. 60
Marta García X
Table 24. Flank wear, Scania used inserts, 120 test specimens. ........................................................... 62
Table 25. Tool life for different techniques, Scania case study. .......................................................... 64
Marta García XI
LIST OF ABBREVIATIONS
Al2O3 Aluminium oxide
BUE Built up edge
CFD Computational Fluid Dynamics
CLF Cooling Lubricating Fluids
CNC Computer Numerical Control
CVD Chemical Vapour Deposition
ECEA Cutting edge angle
ENP Engineered NanoParticles
FE Finite Element.
FOV Field of View
GDP Gross Domestic Product
ICP -MS Inductively coupled plasma mass spectrometry
IR Infrared
MoS2 Molibdenum Disulfide
MWF Metal Working Fluid
MQL Minimum Quantity Lubrication
MWF Molibdenum Disulfide
nCLF Nano-Cooling Lubricating Fluids
NF NanoFluid
PVD Physical Vapour Deposition
TiC Titanium Carbide
TiN Titanium Nitrate
TiO2 Titanium dioxide
Marta García XII
LIST OF NOMENCLATURE
Symbol Parameter Units
µ Vicosity cP
Ap Cutting depth mm
d Insert size/Cutting edge length mm
Fc Cutting force N
fc Feed mm/rev
fr Feed rate mm/min
lc Length of cut mm
n Spindle speed rpm
NR Nose radius/ Corner radius mm
Pc Flank wear µm
Ra Arithmetical mean surface roughness µm
Rai Theoretical mean surface roughness µm
Rq Root mean square surface roughness µm
Rz Ten points mean surface roughness µm
tc Machining time s
Tc Cutting temperature ºC
VB Flank wear µm
Vc Cutting speed m/min
ρ Density g/cm3
KTH Royal Institute of Technology Introduction
Marta García Tierno 1 of 88
1 INTRODUCTION
1.1 Background
The concept of sustainability directly affects to all the stages in the production chain. Nowadays
the corporative strategy of a company should be developed integrating sustainability as a major
concept. Sustainable manufacturing is defined as making products and pieces from processes,
which have minimal environmental impact, safe for consumers, energy and resource efficient and
economically feasible. Sustainable manufacturing should involve both the process and the system
level. The material processing technologies are included in the process level and a fundamental part
of them is the need of cooling and lubricating.
Cutting fluids have several functions in material processing technologies, such as lubrication,
cooling and chip removal. Usually the cutting fluids, also known as cooling-lubricating fluids (CLF)
are toxic and dangerous for the nature and the human health. The disposal of these fluids also
needs a special attention and there is strict environmental legislation in this regard. In order to
reduce the quantity of CLF used in machining processes it is desirable to machine in dry or near
dry environments. Minimum Quantity Lubrication (MQL) is a lubrication technique in which a
very small quantity of lubricant is applied on the cutting zone with high precision. It goes from
flow rates of litres per minute with conventional flood cooling methods to 2-100 millilitres per
hour flow rates with MQL systems. The benefits of the method could be synthetizing in [1]:
• Reduction of friction.
• Improvement of surface finish.
• Better removal of heat and its consequent reduction of temperature.
• Tool wear reduction and increase of tool life.
Of course, a reduction of flow of lubricant is also considered a positive impact of MQL.
In recent years nanoparticle-based cooling-lubricating fluid (nCLF) have been designed and
produced by suspending engineered nanoparticles (ENP) in conventional lubricants, for example
vegetable-based oils. These vegetable oils are biodegradable and not hazardous for the nature and
the human health, but the influence of the nanoparticles suspended on should be considered.
The usage of ENP increases both the heat transfer capabilities and the tribological properties of
the lubricants. Previous research in using nanotechnology to improve the lubricants’ properties has
been developed in KTH in the department of Production Engineering (IIP). The results of this
experiments and research have been published in the form of papers in prestigious publications
[2].
KTH Royal Institute of Technology Introduction
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1.2 Objectives
The main objective of this project is to study the performance of the MQL technology using
vegetable base oil and using cooling-lubricating fluids modified with nanoparticles for two different
set-ups and case studies. How the use of this new coolants improves the results obtained in material
processing level.
For this aim, a scientific analysis between three different lubrication techniques will be employed:
• MQL using vegetable-based oil.
• MQL using nCLF, also called in this project NanoFluids, NF.
• Dry machining.
Some of these techniques are widely known and developed but will be used due to the need to
compare the results obtained with the new nanofluids.
The nanoparticle-based cooling-lubricating fluid selected for the experiments must be
economically and environmentally sustainable, which means that it should not be harmful to health
and the environment and must be economically feasible and produced.
The MQL technique can efficiently reduce the associated environmental impact produced by the
disposal of the lubricants. Due to the development of nanoparticles suspended in the CLF the
results can be greatly improved.
The literature review presented in the next chapter shows that the benefits of introducing this kind
of fluids in machining processes, especially in turning, are significant. In most of these articles three
different cooling-lubricating techniques are compared, sometimes including also flood cooling.
Mostly, empirical models have been developed to predict the tool wear evolution and tool life,
usually utilizing home-made MQL systems. The potential of this research resides also in the fact
that the utilized booster is a high-performance booster available in the market. This makes the
project more interesting from the side of the companies involved.
The second part of the project is focused on experimental work for a well-known automotive
Swedish company. This fact gives the opportunity to test the potential of this technology in an
industrial process that it is being used for production, and how this process can be improved and
make it more sustainable.
The scope of this master thesis has a time limitation. It is restricted to the experimental work of
turning two different materials for two case studies that will be explained in detail in the following
sections.
KTH Royal Institute of Technology Introduction
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1.3 Thesis structure
The master thesis consists in 6 chapters. The project is structured separating two big groups of
results: Pre-hardened steel experiments and Scania case study. Common material and information
is presented in previous chapter: State of art and Experimental methodology. Four Appendix, A
to D, are added at the end of the document to extend and complete the information about some
relevant topics.
• Background of the problem
• Thesis scope and objectives
• Calendar of the project (Gantt)
Chapter 1. Introduction
• Explain the following, based on published literature:
• Minimum Quantity Lubrication Technique, its main characteristics, advantages and restrictions.
• Nano-cutting fluids development and advantages.
Chapter 2.State of art
• Planning of the experimental work.
• Explain the process followed to conduct the research, facilities and set-up.
• Collection of relevant variables and MQL system description.
Chapter 3. Experimental methodology
• The results from the experimental study to evaluate the potental of MQL technology for machining pre-hardened steel Toolox 44.
• Tool wear and tool life, temperature and chips.
Chapter 4. Results and discussion.
Toolox® 44
• The results from experimental study to evaluate the potential of MQL technology and Nano-cutting fluids for machining grey cast iron, Scania case study.
• Tool wear and too life, temperature and surface roughness.
Chapter 5. Results and discussion.
Scania case study
• Conclusions and future work in the topic. Chapter 6.
Conclusion and future work
Figure 1. Structure of the master thesis.
KTH Royal Institute of Technology Introduction
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1.4 Collaborators
This project is being supported by the company LetsNano AB and it is done in collaboration with
Accu-Svenska AB. Scania AB is in close contact with KTH, and they understood the potential of
this technology, thus a case study to test the system in one of their processes was proposed.
1.4.1 LetsNano AB
LetsNano AB is a start-up grown at KTH. Their occupation is focused on the developing and
production of Nanofluids for lubrication, heat transfer and energy storage. This Nanofluids that
they produce provide several benefits, such as reduced down time from change events, reduced
thermal deformation of workpiece, better surface finish, reduced consumption of CLF, improve
tool life by reducing tool wear rate or absence of toxic additives giving a healthier working
environment [3].
1.4.2 Accu-Svenska AB
Accu-Svenska AB is a supplier of products and services for MQL systems to industrial applications
of all kinds. Their entire offerings include an ecological profile; and lubricants are brought to
customers directly from the nature with no additives. MQL System is completely designed and
produced in Sweden. The system meets the entire EU standards through the reach directive in
order to be an exempt from the restrictions. The system is completely sustainable; and it does not
expose any environmental or personal health risks [4].
Accu-Svenska AB has been active in industrial lubrication and cooling technology since 1996.
During the first ten years, the company was an agent of the Accu-Lube GmbH, one of the world’s
leading company in production of MQL systems. To meet today’ demands and needs of Swedish
industry for quality health and environment, Accu-Svenska AB developed its unique MQL system
n that is a competent Programmable Logic Controlled, PLC, application system. The system is
exclusively used in conjunction with Accu-Svenska’s self-produced vegetable-based oil. The system
launched to the market in 2006; and it is offered with performance guarantee. It is the only MQL
system that employs Accu-Svenska’s special-processed vegetable-based oil that contains no
additives of any kind [5].
Figure 3. Accu-Svenska AB [4].
Figure 2. LetsNano AB [3].
KTH Royal Institute of Technology Introduction
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1.4.3 Scania: Case study
Scania AB is a major Swedish automotive industry manufacturer of commercial vehicles –
specifically heavy trucks and buses. It also manufactures diesel engines for heavy vehicles as well
as marine and general industrial applications. Scania AB was formed in 1911 through the merger
of Södertälje-based Vabis and Malmö-based Maskinfabriks-aktiebolaget Scania. The company's
head office has been in Södertälje since 1912. Today, Scania has production facilities in Sweden,
France, Netherlands, India, Argentina, Brazil, Poland, and Russia. In addition, there are assembly
plants in ten countries in Africa, Asia and Europe. Scania's sales and service organization and
finance companies are worldwide [6].
Figure 4. Scania AB [6].
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1.5 Time planning
In this section, the temporary planning of the thesis is presented. Firstly, Table 1 shows the
decomposition of the work packages, including start and end days of the tasks. Once the
decomposition in work packages is done, the Gantt diagram is made with the help of Microsoft
Project software. The diagram is shown in Figure 5. During the development of the project the
progress was presented in various presentations. These presentations have been set in the time
planning as milestones.
Table 1. Work packages decomposition.
KTH Royal Institute of Technology Introduction
Marta García Tierno 7 of 88
Fig
ure
5. G
antt
dia
gram
of th
e m
aste
r th
esis
.
KTH Royal Institute of Technology State of the Art
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2 STATE OF THE ART
2.1 Sustainable manufacturing in machining
Machining is the most widely extended industrial process, especially machining of metal products.
In the last years, sustainability in manufacturing is becoming a key issue due to strict environmental
legislation and the necessity of reuse and recycle materials. But for the companies adopting
sustainable strategies would suppose a big effort and investment for the first years. Achieving
sustainability in manufacturing should consider aspects in all levels: system, process and product
levels, trying to find a general view of all them. Concretely the main objective of the sustainable
manufacturing is to change from the classical ideology of manufacturing based on increase the
productivity to a new vision focus on the concept of global value. There is not an official definition,
but the recent work describes it as a process that leads to [7, 8]:
• Environmental friendliness.
• Reduced cost.
• Reduced power consumption.
• Reduced wastes.
• Enhanced operational safety.
• Improved personnel health.
Sustainable manufacturing
Enviromental Friendliness
Machining cost
Power Consumption
Waste Management
Operational Safety
Personnel Health
Figure 6. Basic elements of sustainable machining [8].
KTH Royal Institute of Technology State of the Art
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By changing usual practices in metal cutting sector to sustainable activities would benefit the
company economically, ecologically and socially. In the metal machining sector, a fundamental part
are the cutting fluids. These fluids have several functions, such as lubrication, cooling or chip
removal.
The usual cutting fluids,CLF, the ones that are used for flood cooling are an emulsion, made with
water and oil, usually up to 90% of water. This water must be recycled because it is hazardous for
both the environment and the human health. They can cause problems to human skin and pollute
the soil. These cutting fluids affect directly to some all the basic elements to achieve sustainable
manufacturing, shown in Figure 6.
Klocke and Eisenblätter [9] studied the influence of CLF emulsions in the total cost of the
machining process. The conclusion was that the 15% of the total cost of machining is due to the
CLF emulsions, while the cost fraction of tools is only 4%.
These are also important reasons, not only environmental but also economic reasons, for
developing new cooling and lubrication techniques such as dry or near dry machining or MQL.
The main drawback that the mentioned techniques must deal with is the quality of the results. This
problem is even harder machining difficult-to-cut materials, such as titanium and nickel base alloys
or hardened steels.
2.2 Tribology of metal cutting
The complexity of the machining processes makes very difficult to define systematic friction and
wear mechanisms. The detailed information of what happens in the interface between the tool and
the workpiece is particularly important to understand control and design the machining processes.
The optimization of the processes can be achieved by understanding the tribology of the contact
between tool and workpiece.
Tribological contacts are usually defined by pairs of bodies in contact. This contact is characterized
by a basic body, as an element subjected to the wear, and a counter body [10]. In any machining
process the basic body Is the tool and the counter body the machined workpiece. But apart from
the contact and interfacial element itself the cutting process needs to be understood as a whole and
keep all the parameters of the cutting process under control. All these variables have a direct
influence and impact in one of the main studies of the tribology: the wear (Figure 7). The main
wear mechanisms present in the cutting inserts are abrasion, adhesion, tribochemical reactions and
surface damage. This wear mechanisms of cutting tools often detrimentally limit the performance
of cutting processes. The complexity of a machining process makes it difficult to systematically
analyse the friction and wear mechanisms at the active areas of the tool [11].
KTH Royal Institute of Technology State of the Art
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Focusing on the interfacial element in the cutting process, three cooling-lubricating strategies can
be defined: flood-wet cooling (emulsion), MQL (vegetable oil) and Compressed air. The last two
strategies could be considered as a dry or near dry machining, with the benefits that this involves.
As it is said before, the primary functions of the cutting fluids are cooling, lubricating and chip
removing. In Table 2 shows a summary of the functions and how each lubrication strategy is fixing
them.
The conventional coolant, also known as emulsion has other functions such as transporting chips
or cleaning tools, fixtures and workpieces. If the coolant is removed from the process, these
secondary functions must be taken by other components.
Table 2. Lubrication strategies and its functions [10].
Strategy/Function Cooling Lubrication Chip Removal
Emulsion-Flood Excellent Good Excellent
Oil-MQL Good Excellent Good
Compressed air Little No Little
• None
• Comp. air
• Coolant
• MQL
•Properties
•Coating
•Surface
•Cutting speed
•Feed
•Depth of cut
•Hardness
•Toughness
•Structure
WorkpieceCutting
parameters
Interfacial element
Tool
Contact conditions
• Direct stress
• Shear stress
• Temperature
Wear mechanisms
• Tribo. reactions
• Abrasion
• Adhesion
• Fatigue
Figure 7. Cutting process as a tribological system [10].
KTH Royal Institute of Technology State of the Art
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In following subchapters, the lubrication technique that is the focus of this project will be deeply
developed. In addition, a review of the published literature on a new technology is presented,
Nano-cutting fluids and MQL Technique. Nevertheless, to understand the process properly wear
mechanisms should be explained, as an important study field of the tribology.
Tribology is defined as the science that studies the interaction between surfaces in relative motion.
This study includes not only lubrication, but also friction and wear. In tribological contacts wear
occurs due to the interaction between surfaces in contact and implies gradual removal of the surface
materials. The wear mechanisms are abrasive, adhesive, fatigue and tribo chemical wear. Usually an
interrelationship between these types of wear is what occurs in the contacts [12]. To understand
what it is happening in the interface between cutting tool and workpiece material it is important to
explain the wear mechanisms [13].
Adhesive wear
Adhesive wear has its origin from the shearing contact between the asperities of two solid in relative
motion. During sliding elastic and plastic deformation of the asperities occur resulting in a contact
area where the boding forces give the adherence and the surfaces get welded [14].
Abrasive wear
Abrasive wear occurs when one of the surfaces in contact is significantly harder than the other.
Abrasion can also occur when harder particles are introduced in the tribo contact. Abrasive wear
causes high plastic deformation. Harder material of the contact will scratch the softer in a ploughing
action, resulting wear, scratches and grooves in the soft material [14].
Fatigue wear
Fatigue wear is caused by periodical loads. Repeated loads generate microcracks, usually below the
surface, at a point of weakness such an inclusion. On the subsequent loading and unloading, the
microcrack is propagating and voids coalesce. When the crack reaches a critical size, it changes
direction to emerge the surface and a flat sheet-like particle is detached. This wear mechanism does
not usually occur in metal cutting, it is more common in rolls and dies [12].
Tribo chemical wear
Tribo chemical wear is mainly dominated by chemical reactions in the contact and the material is
therefore consumed. The environmental conditions in combination with the mechanical stresses
have great important. The chemical action, such as diffusion or solution, is not a wear mechanism
on its own, but it is in combination with other wear mechanisms. So, it is better to consider
chemical effects as an additional influence parameter which could change the material properties
of the surfaces in contact [12].
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2.3 Minimum Quantity Lubrication Technique (MQL)
If a fluid is applied in the cutting zone, the main lubrication techniques regarding to application
method in machining can be summarized in two groups:
• Flood-cooling. It is the most common lubrication method, but also the most hazardous
and expensive one. It guarantees a very good level of lubrication, cooling and chip
removing. Applying this method of lubrication, it is also possible to orientate the nozzle to
the clearance tool surface, reducing the flank wear, especially when the cutting speed is
slow [15].
• Minimal quantity lubrication (MQL). in MQL very small lubricant flow (ml/h instead
of l/min) is used. In this case, the lubricant is directly sprayed on the cutting area. It
guarantees a good level of lubrication, but the cooling action is very small, and the chip
removal mechanism is obtained by the air flow used to spread the lubricant.
In recent years several researchers have tried to reduce the quantity of lubricant using different
cooling strategies. The most successful technique is the near dry machining or MQL technique,
which is implemented in the market.
MQL [16] is a recent technique introduced in machining obtains safe, environmental and economic
benefits, reducing the use of coolant lubricant fluids in metal cutting. In these methods, high-speed
air jet is introduced with micro-drops of vegetable oil in suspension to lubricate the cutting zone.
In these techniques, lubricate flow rate is limited to millilitres/ hour instead of litre/ min like in
flood cooling environment. This mist or suspension made from air and lubricant should be
delivered accurately into the cutting zone.
First, the lubricant must be mixed with the air to achieve the mist that is being introduced into the
interface of the cutting insert and the workpiece. For this purpose, there are different types of
systems, but in this project a high-performance booster provided by Accu-Svenska AB is the one
chosen. The characteristics of this system will be explained in the following chapter.
Apart from the reduction of temperature and tool wear there are other advantages that MQL
technique can offer [16]:
Figure 8. Flood cooling with Emulsion [15].
KTH Royal Institute of Technology State of the Art
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• Chip, workpiece and tool holder have a low residue of lubricant: their cleaning is easier and
cheaper.
• During machining the working area is not flooded so, if necessary, the cutting operation
can be readily observed.
The successful application of MQL technique in machining processes involves good understanding
of different variables such as feed technology, parameters settings, fluids properties [17]… All the
relevant and parameters that are important for the MQL technique are summarized in the Figure
9. All the components in the MQL system must be very carefully coordinated in order to achieve
the desired outcome, which is optimal, both technologically, economically and environmentally
[10].
2.3.1 Characteristics
The main characteristics of MQL can be described in these points:
• Small amount of fluid. The German DIN specification fix the maximum flow for MQL
up to 50 mL/hour of lubricant and in exceptional cases up to 150 mL/hour. But generally,
the amount is subjective and depends on the material, process and the selected tools [18].
• Lubricant. Since very good lubrication properties are required for the MQL technique,
usually the fluid utilized for this technology is pure oil. It could be from mineral or
vegetable oil to synthetic oils.
• Generation of the mist. The oil in MQL technique is applied in form of a mist. This
mist is formed by compressed air, at a medium pressure, from 2 to 10 bars and the
lubricant itself. The mist should be as much uniform as it is possible. The size of the
droplets depends on the equipment used and the characteristics of the selected oil.
MQL
Equipment
• High performance booster
Fluids
• Vegetable oil
• NF
Machine tool
• Upgradability
Settings
• Oil flow
• Air flow
Tools
• Internal feed
• External feed
Figure 9. Minimum Quantity Lubrication System (MQL) [17].
KTH Royal Institute of Technology State of the Art
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• Accurate application. The oil in MQL must be applied accurately into the cutting zone
to achieve good machining products. It is particularly important to control all the
parameters to ensure that the oil reaches properly the cutting point.
So, the goal of the MQL is simple, apply just enough fluid to fully lubricate the cutting zone using
the least amount of oil as possible. But in this technology, there are also some general factors that
should be considered to obtain good outcomes related to the lubricants, oils, tools, materials and
removal of the chips.
Oils
There are some types of oils that are not the suitable for MQL. Water-miscible metalworking fluids
don not have good enough lubricity properties. On the other hand, their flash point is too low for
the temperatures that could be reach in cutting with MQL.
Lubricants with organic additives or zinc are not the best option since these additives can react at
MQL machining temperatures and cause hazard products. Mineral oil-based products with high
aromatic compound content could also change in relatively short time [18].
Workpiece material
Not all the materials are appropriated to be cut using MQL technology. This decision of selecting
or switching to MQL system depends on mechanical, physical and chemical properties of the
materials.
Grey cast iron works very well with MQL since the graphite liberated during machining acts as an
additional lubricant. Cutting these kind of materials, a significant amount of dust is generated. In
flood cooling this dust is easily removed by the cutting fluid, so if MQL is selected this dust removal
must be considered.
Non-ferrous materials, like some aluminium alloys and steel up to 800MPa of tensile strength are
easy to cut, and therefor suitable for MQL cooling technique. Even difficult-to-cut material, such
as titanium alloys, can be machined with MQL if the system is properly designed.
But also, some materials have demonstrated that they are not suitable for this technology, such as
copper in heavy cutting dur to the heat generation in this process [18].
Tools
In the implementation of MQL technology in a cutting process, the selection of an appropriated
tool can help to minimize the drawbacks and extend the tool life. Tools designed for dry cutting
usually work well with MQL, because they are designed to resist thermal shocks. One example of
this type of tools could be ceramic inserts.
In the machining of high strength steels multi-layer coating tools are recommended. These coatings
help the tool to resist to high temperatures without breaking. Tools can be designed for MQL, with
special chip breakers. Although, these tools may be more expensive, using them might allow
reaching the proper tolerances, cutting faster and obtaining longer tool life [19].
KTH Royal Institute of Technology State of the Art
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Chips
Chips removal in MQL is completely different from chip removal in flood cooling. The main
mechanisms to remove the chips in MQL are gravity and compressed air. In the work space it is
important to remove the chips as soon as possible because they can damage the process in different
aspects (e.g. workpiece and machining equipment).
The design of the workspace can help removing the chips in MQL technique. The gravity is the
simplest method, designing an inclined metal sliding into a collector or onto a conveyor [18]. The
position of the workpiece also helps in the chips removal. Compressed air also can be used to
remove the chips. But the mist for lubricating and the air should go in separate nozzles [20].
2.3.2 Advantages
Related to the application of this technology into the industry, there are many known advantages
that the MQL technology could provide. MQL has demonstrated in multiple worldwide plants
with better quality, higher productivity, minimal environmental impact, lower operation health
issues, reduced water and greenhouse gas emission, and reduced energy consumption, which result
in lower overall cost [21]. The main advantages that MQL could provide to the industry can be
summarized in five points:
Costs
The MWF associated costs are in the range of 10-20% of total manufacturing cost. By changing
this type of flood cooling method to MQL most of the costs associated to MWF can be reduced
or eliminated [19].
In Figure 10 the costs analysis in metal machining re shown in detail. This 16% of costs would be
reduced, because the MQL energy consumption is very small, the disposal is zero, the investment
for the system itself is much cheaper compared to the system of wet machining, and MQL does
not need extra work from the employers.
16%
4%
80%
MWF costs Tools Other costs
14%7%
10%
40%
22%
7%
WF system
Energy
Employees
System
Disposal
Others
Figure 10. Metal working fluid costs in metal machining [20].
KTH Royal Institute of Technology State of the Art
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Energy consumption
The largest energy consumption in CNC machines with traditional flood cooling are:
• 25% in the cutting process itself.
• 30-40% in the MWF system.
• 15-20% to obtain the necessary compressed air for flood cooling.
In traditional flood or wet machining, the energy consumption is mostly fixed and difficult to
reduce, it can only be reduce improving the tooling and cutting efficiency. Using MQL technology
this energy related to MWF system and compressed air no longer exists (≈50% of the total energy
consumption), which results in savings in energy.
Environment and safety
MQL is considered as a low-emission process due to a considerable reduction of MWF inhaled
and skin compared to flood machining. A study by a German association shows that turning under
MQL and wet conditions has confirmed that the concentration of oil is less than the half in MQL
and always below the inhalable fraction for a human (10 mg/m3) as it is shown in this figure, in
which are presented the results of measuring the concentration of oil in the air in three different
points of the turning process [22].
25%
25%
15%
35%
0,00%
20,00%
40,00%
60,00%
80,00%
100,00%
ENERGY CONSUMPTION WET MACHINING
MWF System
Compressed air
Cutting process
Others
Figure 11. Percentage of energy consumption in wet machining [18].
0
2
4
6
8
10
12
14
16
18
Person Control Panel Extracted air
EM
ISSIO
N [M
G/
M3 A
IR]
MEASUREMENT POINT
MQL
Wet
Figure 12. Comparison of emission during machining between wet
and MQL turning [22].
KTH Royal Institute of Technology State of the Art
Marta García Tierno 17 of 88
Chips recycling
Revenue from chips re-melting is often a significant component in plant’s operating budget. Drying
and cleaning the chips produced after wet machining requires floor space, energy and it is
expensive. In the use of MQL the chips are nearly dry and virtually clean, that is why there is not
necessary to dry them [21].
Nano-cutting fluids
Addition of Engineered Nano Particles (ENP) to base fluid enhance tribological and thermal
properties, so the quality of the product obtained after the process could also be enhanced. This
technology is very new, and it is being developed continuously. In the next subchapter the main
advantages and literature published in this technology will be discussed.
2.3.3 Heat management in MQL
One of the main objectives of the cooling-lubrication technologies in metal cutting is to absorb
the heat generated in the cutting zone, which could be translated in reduction in temperature.
In metal cutting there exist to main zones in where the heat generation is occurring: Primary and
secondary shear zones (Figure 13).
The primary heat is difficult to reduce, and the only possible solution is to try to reduce its effects.
That is the main function of the conventional cutting fluids, to go into the effect instead of looking
to the source of the heat. This rapid cooling achieved by conventional cutting fluids has also some
drawbacks. If the tool is cooled down too fast, it can cause a sudden breakage due to thermal cracks
in the tool. This rapid heating and cooling phenomena in the tools is called thermal cycles.
On the other hand, MQL technology focuses on the elimination of the heat generated by the
friction, in the secondary shear zone, between the tool and the chip interface. The heat generated
in this zone is one of the main reasons for premature tool wear [18]. In this case the major part of
the generated is taken by the chips. The temperature is reduced both in the workpiece and in the
cutting insert. Improving the thermal properties of the MQL lubricants could also help reducing
the temperature in the cutting point.
Figure 13. Heat generation in metal cutting [19].
KTH Royal Institute of Technology State of the Art
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2.4 Minimum Quantity Lubrication (MQL) using Nano-cutting
Cooling Fluids
One of the main objectives of the cutting fluids is cooling the interface of the cutting tool and the
workpiece. A Nanofluid (NF) is designed and fabricated by suspending engineered nanoparticles
(ENPs) in biodegradable vegetable-based fluids. The addition of this Nanoparticles into
conventional oils improves its thermal properties, which means and improvement of cooling
capabilities. These Nano-cutting fluids are expensive to produce, so they are not advisable for wet
or flood machining. But the small amount of flow that MQL provides can make Nanofluids a
viable alternative [23].
Several parameters affect directly to the machining process: cutting forces, type of cutting tool,
temperatures… But it is found that the most influential one is the temperature[24]. One of the
main functions of the cutting fluids is the control of the temperature during the process. The
cooling fluid prevents the rise of temperature, preventing also the thermal expansion of the
workpiece. Consequently, the cutting fluids enhance the tool life and the quality of the machined
piece. Using MQL techniques instead of traditional flood-cooling high cooling is needed to be
achieve with very small quantity of lubricant. Thermal conductivity increases introducing
nanoparticles into conventional oils, which improves its cooling capabilities.
But this improvement of the thermal properties of the cutting fluid is not the only advantage of
adding nanoparticles into the oil. There is also a reduction in the friction recorded due to the
addition of ENP. This phenomenon could be explained by the following mechanisms [25].
Ball-bearing effect. The nanoparticles suspended in the oil play the role of a ball between the two
lubricated surfaces, reducing the friction between them.
• Protective film. The nanoparticles protect the surface by coating the rough surfaces.
• Mending effect. The ENP can help reducing the loss of mass in the surfaces. This effect
also reduces the surface roughness or the workpiece.
• Polishing effect. The nanoparticles help in the abrasion of the surface, which is known as
a polishing effect. This effect is very important and one of the main reason of using ENP
in metal machining processes.
Figure 14. Possible lubrication mechanisms by the application of Nano-oil between the frictional surface [25].
KTH Royal Institute of Technology State of the Art
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The literature written and published about cutting fluids enhanced with Nanoparticles is wide and
varied, trying to prove the potential that this new technology has in metal machining. Researchers
used different MQL techniques for their experiments, but the flow of oil that they supply is always
limited to millilitres per hour, instead of the litres per minute of the traditional flood cooling. In
this chapter the literature and papers found in this topic will be summarize.
Krishna et al. [26] performed a study to prove the potential of nanoboric acid suspensions in two
different base oils, SAE-40 and coconut oil. The material turned was AISI 1040 stainless steel with
carbide tools. They tried with different concentrations of Nanoparticles as well, obtaining the best
performance in terms of cutting temperatures, tool wear and surface roughness at 0.5% nanoboric
acid suspensions in coconut oil.
Rao et al. [27] studied the behaviour of different concentrations, from 0,5 to 1% of carbon
nanotube (CNT) inclusions in the oil turning of AISI 1040 stainless steel and cemented carbides.
The obtained results in terms of nodal temperatures and tool wear showed and reduction in
temperature and flank wear comparing with traditional cutting fluid. The results in both
temperature and wear remain constant at concentrations of more than 2%. Variation of
temperature and flank wear are shown in Figure 15.
Khandekar et al. [28] run a comparative study of tool wear, cutting force, surface roughness and
chip thickness among dry turning, conventional cutting fluid as well as Nano-cutting fluid (1%
weight of Al2O3). The material was AISI 4340 steel, machined with uncoated cemented carbide
inserts. Machining with Nano-cutting fluid shows a significant reduction in the surface roughness
of 54.5% and 28.5% compared to dry machining and traditional cutting fluid.
Amrita et al. [29] utilized three types of Nano-cutting fluids in turning AISI 1040 hardened steel.
This oil includes 0.3 wt.% of graphite, nanoboric acid and MoS2. In general terms the better
properties were shown by the Nano-cutting fluid made with MoS2.
Figure 15. Variation of flank wear and nodal temperature with machining time [27].
KTH Royal Institute of Technology State of the Art
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Sharma et al. [30] examined the machining performance of a Nano cutting fluid prepared with
Al2O3 1 wt.% in turning a workpiece of AISI 1040 steel, using also MQL technique. The study
reveals clear reduction in tool wear and surface roughness compared to dry, conventional oil MQL
and wet machining. MQL shows the machining performance comparable to wet machining. In
other study performed by Sharma et al. [31] tried with TiO2 analysing forces, tool wear, surface
roughness and chip morphology. The obtained results are comparable in quality to the ones
obtained with Al2O3. The results obtained in tool wear for both types of Nanoparticles are shown
in Figure 16.
Su et al. [32] investigated the effect of Nanofluid with Nano-graphite using ester oil as base fluid
in turning of AISI 1045 medium carbon steel. Two different cutting speeds (55 m/min and 96
m/min) were tried finding a decrease in main cutting force with respect to dry cutting of 11 and
26% respectively, with the oil improved with 0.5 wt.% of Nano-graphite. On the other hand, the
maximum percentage of reduction in cutting temperature relatively to dry cutting was 11,9% and
21%, with 0.5 wt.% of Nano-graphite as well.
Chetan et al. [33] conducted an experimental study using MQL technique with Nanofluids
produced with commercially available powder of alumina (Al2O3) and colloidal solution of silver
(Ag) in sunflower oil in turning of Nickel based alloy. The lowest magnitude of cutting force and
flank wear were found with alumina NF and a flow rate of 125 ml/h.
The potential of the fluids enhanced with Nanoparticles and MQL technique is also tried to be
prove in other cutting processes such as milling or grinding, not only in turning, the case study of
this project. Uysal and Furkan Demiren [34] performed a research of milling Martensitic stainless
steel AISI 420 by using vegetable oil reinforced with 1wt.% of MoS2. Surface roughness and tool
wear results were analysed. These experimental results showed that the use of nanoparticles of
MoS2 gave the minimum tool wear and surface roughness due to the lubrication effect of the
nanoparticles. In Figure 17 Surface roughness is shown for Dry cutting, MQL with conventional
oil MQL with MoS2 nanofluid.
Figure 16. Flank wear vs. machining time 4 cooling techniques and two Nanofluids 1. Al2O3 and 2. TiO2[30, 31].
KTH Royal Institute of Technology State of the Art
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Sarhan et al. [35] studied the behaviour SiO2 nanoparticles with MQL technology in milling
aluminium alloy AL6061-T, commonly used in the aircraft and automotive industries for its
extraordinary mechanical properties. The main objective of this research is to reduce the power
consumption and pollution, so power and specific energy were also measured. In Figure 17,
evolution of specific energy and power reduction are shown vs. cutting time. The power reduction
in percentage is 30% during in all the cutting measured steps. The results show that the cutting
forces, specific energy, and the power required at the cutting tool are reduced considerably using
the lubricant made out SiO2 and vegetable oil. Sayuti et al. [36] investigated the machining
performance of Aluminium AL6061-T6 alloy also, under MQL cooling technique and Nanofluids
with SiO2 nanoparticles. This study was focused on the machined surface in the end milling of this
aluminium alloy. The results show that the machined surface contain a thin protective film of SiO2,
and this helps to reduce the friction and thermal deformation between the tool and the workpiece.
Sayuti et al. [37] an experimental study in milling aerospace duralumin AL-2017-T4 using carbon
onion nanofluid. The highest carbon onion concentration (1.5 wt.%) produces the lowest cutting
force and the best surface quality. A reduction of 21,99% in cutting forces and 46.32% in surface
roughness are recorded.
Figure 17. Specific energy and power reduction for both lubrication mode [35].
Figure 18. Variation of surface roughness with cutting condition [34].
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Rahmati et al. [38] investigated the effects of MoS2 on the machined surface morphology after
milling aluminium alloy AL6061-T6 workpiece. The best machined surface quality was found with
0.5% of MoS2. The same researches in another investigation with aluminium alloy AL6061-T6 [39]
investigated with different concentration of MoS2, pressures and nozzle orientation angle. One of
the main conclusion that could be extracted from this research is that the minimum cutting force,
cutting temperature and the best surface roughness were achieved with an air pressure of 4 bars.
Mao et al. [40] performed experiments with different types of nanoparticles and base oils in
grinding process of hardened AISI 52100 steel. The results in surface roughness and cutting forces
showed with oil-based nanofluid in comparison with water-based nanofluid, but not cutting
temperatures. This shows that the oil has better lubrication properties, but the water-based NF has
a better cooling effect. The size of the nanoparticles only affects to the forces, decreasing with the
size of them, and to the surface finish, that is deteriorated at the larger diameter nanoparticles.
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Table 3. Summary of MQL with NF with different nanoparticles literature for turning process.
No. Strategy/ Authors
Cooling methods
Workpìece/ Tooling
Cutting Parameters
Findings
1 Krishna et al., (2010) [26]
MQL+NF SAE 40 and coconut oil, 0.25-1 wt.% nanoboric acid NP (50nm)
AISI 1040 steel Cemented carbide tools MQL Tool holder
Vc=100m/min f=0,2mm/rev d=1mm
Thermal conductivity increased, and specific heat decreased with the concentration of NP. Best performance in surface roughness and temperatures at 0,5 wt.% of NP.
2 Rao et al., (2011) [27]
Dry, MQL and MQL+NF CNT (Carbon nanotube) nanoparticles 0.5-5 wt.%
AISI 1040 steel Cemented carbide tools
Vc=102m/min f=0,44mm/rev d=0,5mm
The decrease of tool wear and nodal temperature is limited to 2 wt.% of nanoparticles in the oil
3 Khandekar et al., (2012) [28]
Dry, MQL and MQL+NF 1 wt.% Al2O3
AISI 4340 steel Uncoated carbide tools
Vc=350m/min f=0,1mm/rev d=1mm
Great reduction in crater and flank wear. Reduction of 50% and 30% in cutting force and 54,5% and 28,5% in Ra compared to dry and machining with conventional cutting fluid.
4 Amrita et al., (2014) [29]
Dry, Wet, MQL and MQL+NF NanoGraphite, Nanoboric acid and MoS2 NP 0.3 wt%
AISI 1040 steel Uncoated cemented carbide tools
Vc=65m/min f=0,14mm/rev d=0,75mm
Oil with MoS2 shows better performance in cutting forces. NanoFluids, starting with MoS2 showed better results in terms of tool wear, even better than wet machining.
5 Sharma et al., (2016) [30]
Dry, Wet, MQL and MQL+NF 1 wt.% Al2O3
AISI 1040 steel Uncoated cemented carbide tools
Vc=96,7m/min f=0,1mm/rev d=1mm
NF reduced cutting force up to 59.1%, 29.2% and 28.6% compared to dry, conventional mist and wet machining, respectively. Tool wear up to 63.9%, 44.9% and 5.27%. The machining performance is comparable to wet machining.
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6 Sharma et al., (2016) [31]
Dry, Wet, MQL and MQL+NF 1 wt.% TiO2
AISI 1040 steel Uncoated cemented carbide tools
Vc=96,7m/min f=0,1mm/rev d=1mm
NF reduced cutting force up to 62.67%, 34.88% and 35.85% compared to dry, conventional mist and wet machining, respectively. Tool wear up to 58.1% and 35.85%, compared to dry and conventional oil. The machining performance is comparable to wet machining.
7 Su et al., (2015) [32]
Dry, MQL and MQL+NF 0.1-0.5 wt% NanoGraphite
AISI 1045 steel Uncoated carbide tools
Vc=55/96mm/min f=0,1mm/rev d=1mm
The main cutting force with respect to dry cutting was 11 and 26 %, for the two selected cutting speeds. The maximum reduction of cutting temperature relative to dry cutting was 11.9 and 21% respectively for the different speeds.
8 Chetan et al., (2016) [33]
Dry, MQL and MQL+NF 0,1-10 wt.%Al2O3 and Ag
Nimonic 90 Nickel based alloy Multilayered carbide inserts
Vc=60 mm/min f=0,12mm/rev d=0,5mm
The smallest flank wear obtained was with the lowest flow and Al2O3 NF. Best surface quality also with Al2O3 in sunflower base oil.
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Table 4. Summary of MQL with NF with different nanoparticles literature for milling process.
No.
Strategy/ Authors
Cooling methods
Workpìece/ Tooling
Cutting Parameters
Findings
1 Uysal and Furkan Demiren, (2015) [34]
Dry, MQL and MQL+NF 1 wt% MoS2
AISI 420 martensitic steel Uncoated WC cutting tools
n=995 1/min f=180mm/min d=0,5mm
Two flows were tested (20-40mL/h), not seeing a big difference. The reductions of the surface roughness were determined as 36,3% and 39,2% at 20 ml/h and 40 ml/ flow rates in nano MQL. The nano MQL method could reduce the tool wear by 16,8% and 19,9% at 20 ml/h and 40 ml/h flow
2 Sarhan et al., (2012) [35]
MQL and MQL+NF 0.2 wt% SiO2
Al 6061-T6 Aluminium alloy HSS with 2 flutes and 10 mm diameter
n=5000 1/min f=100mm/min d=5mm
The range of cutting force reduction is 40.22–42.13% compared to conventional oil. Power consumption analysis was also done obtaining a range of reduction of 40.22-42.13%.
3 Sayuti et al., (2014) [36]
MQL and MQL+NF 0.2-1 wt% SiO2
Al 6061-T6 Aluminium alloy HSS with 2 flutes and 10 mm diameter
n=5000 1/min f=100mm/min d=5mm
Protective thin films were developed on the feed marks of the machined surface providing much less friction and thermal deformation. Drastic reduction of cutting oil consumption using MQL+NF was recorded.
4 Sayuti et al., (2013) [37]
MQL and MQL+NF 0.5-1.5 wt% Carbon onions
Duralumin AL2017-T4 Aluminium alloy SEC-ALHEM2S8 end mill, 8 mm diameter
n=5000 1/min f=75,408-100mm/min d=5mm
The highest carbon onion concentration (1.5 %wt) produces the lowest cutting force and best surface quality. The cutting force and surface roughness reduction percentage are found to be 21.99 and 46.32 %.
5 Rahmati et al., (2014) [38]
MQL and MQL+NF 0.2-1 wt% MoS2
Al 6061-T6 Aluminium alloy Tungsten
n=5000 1/min f=100mm/min d=5mm
Machined surface quality was superior when NP of 0.5 wt% concentration. NP in the tool-workpiece
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carbide, 2 flutes and 10 mm diameter
interface enhanced the machined surface due tothe rolling, filling and polishing actions.
6 Rahmati et al., (2014) [39]
MQL and MQL+NF 0.2-1 wt% MoS2
Al 6061-T6 Aluminium alloy Tungsten carbide, 2 flutes and 10 mm diameter
n=8000 1/min f=2100mm/min d=5mm
Minimum cutting force with 1 wt.% and 30º nozzle angle. Minimum temperature with 0.5 wt.% and 30º nozzle angle. Best surface roughness with 0.5 wt.% and 60º nozzle angle. The best performance is found with air pressure of 4 bars.
7 Mao et al., (2013) [40]
MQL and MQL+NF (Grinding) 0.2-1 wt% MoS2
AISI 52100 Vc=31,4m/s f=0,05m/s d=0,01mm
The lubricating and cooling performance in the grinding zone are improved with the increase of the NP concentration. Not significant influence on the diameter of the NP.
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2.5 Previous work at KTH-IIP
Krajnik et al. [2] performed in 2016 experimental work at KTH-IIP laboratory, machining
experiments of MoS2 based nCLF in turning of hardened steel. Three cooling-lubricating
techniques were compared: flood cooling, MQL using vegetable-based soya bean oil and this base
oil enhanced with NP, 1% wt. MoS2, 10 nm co-axial nanotubes. The workpiece material is Toolox®
44, pre-hardened steel. The properties of this material will be explained in detail in experimental
methodology chapter, since it is the material selected for the current work
The machining experiments were carried out on a Swedturn 300 (SMT) CNC lathe machine.
Characteristics of metal-working process kept into consideration were tool wear evolution, tool
life, chip formation and temperature evolution (only for MQL and nCLF). Figure 19 shows the
evolution of tool wear vs. number of cuts for one measurement and three cooling techniques. It
can be observed that there is systematic reduction in evolution of flank wear each step of all three
measurements, for three lubrication methods. Also, there is apparent increase in tool life in nCLF
based lubrication method when compared with flood and MQL lubrication.
Figure 19. Tool wear vs. number of cuts [2].
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3 EXPERIMENTAL METHODOLOGY
3.1 Planning of the experiments
The experiments were focused in turning under dry, vegetable base oil for MQL and new
developed Nano-cutting fluids in CNC turning machine. The steps for running these experiments
are the following:
1. Problem statement. to investigate the potential of MQL technique and specially MQL
technique using Nano-cutting fluids in turning of two different materials, pre-hardened
steel (Toolox® 44) and grey cast iron (Scania case study).
2. Objectives. The main aim of this project is to measure different variables in the machining
process to prove the potential of this technology in different conditions. The secondary
aim could be study if this technology could be used as an alternative cooling technology in
industrial machining process.
3. Selection of the measurable variables. Considering which facilities were available in
KTH-IIP laboratory the influencing measurement variables were selected. Tool wear
mechanisms and tool life, surface roughness and cutting temperature will be measured.
4. Selection of the cutting parameters. This step of the planning was particularly important
since it affects directly to the succeed of the experimental work.
5. Experimental work. Execution of the experimental work, following the planned steps
and decisions.
6. Results and analysis. Analyse the collected variables and interpret the results. The
experiments were repeated to validate them and find repeatability.
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3.2 Experimental set-up
3.2.1 CNC turning-lathe machine
Turning experiments were conducted in CNC lathe turning machine SMT Swedturn 300 [41]. Each
experiment was repeated at least two times to avoid possible errors.
Table 5. General technical data SMT Swedturn 300 [41].
Some general definitions and formulas should be defined in order to understand the turning
process properly. Turning generates cylindrical and rounded forms with a singlepoint tool. The
tool is stationary with the workpiece rotating. Turning is the most common process for metal
cutting and is a highly optimized process, requiring thorough consideration of the various factors
in the turning application [42].
Some equations should be presented to comprehend turning process and to calculate subsequently
the cutting parameters [43]:
Max distance
spindlenose - ref.plane
Machine weight
(approx)
Spindle
drive
Number of
spindle speeds
1295 mm 8000 kg 40 kW Stepless
Figure 20. Schemetic and picture SMT Swedturn 300 [41].
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Cutting speed vc (m/min) 𝑣𝑐 =𝐷2×𝜋×𝑛
1000
Spindle speed n (rpm) 𝑛 =𝑣𝑐×1000
𝜋×𝐷2
Metal removal rate Q (cm3/min) 𝑄 = 𝑣𝑐 × 𝑎𝑝 × 𝑓𝑛
Machining time Tc (min) 𝑇𝑐 =𝑙𝑚
𝑓𝑛×𝑛
Cutting depth ap (mm) 𝑎𝑝 =𝐷1−𝐷2
2
Net power Pc (kW) 𝑃𝑐 =𝑣𝑐×𝑎𝑝×𝑓𝑛×𝑘𝑐
60×103
Table 6. Turning parameters.
Symbol Designation Unit
D1 Initial diameter mm
D2 Machining diameter mm
fn Feed per revolution mm/rev
ap Cutting depth mm
n Spindle speed rpm
Pc Net power kW
Q, MRR Metal removal rate cm3/min
Tc Machining time min
lm Machining length mm
ap
n
fn
Vc
Figure 21. Schematic diagram of turning operation and cutting parameters [43].
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3.2.2 Workpiece material
The metal cutting industry produces an extremely wide variety of components machined from
different materials. Each material has its own characteristics that are influenced by heat treatments,
alloying elements…
Therefore, workpiece materials have been divided into six groups according to ISO-standard.
Toolox® 44 is pre-hardened steel and its hardness value is 45 HRC. Regarding to the ISO-standard
this material should be part of two groups: ISO H and ISO P. Its hardness is 45 HRC, which is the
limit between hardened steel and usual steel.
• ISO H. Hardened steel is the smallest group of steels from a machining point of view.
This group contains hardened and tempered steels with hardness between 45 and 65 HRC.
The hardness makes them all difficult to machine. The material generates heat during
cutting and it is very abrasive for the cutting tool.
• ISO P. It is the largest of all the workpiece material groups. This group includes unalloyed
to high-alloyed materials, martensitic and ferritic stainless steel… The machinability of
these steels differs a lot depending of the properties of the material: hardness, carbon
content etc. [44].
• ISO K. Machining cast is completely different from machining steel, and there many
difference as well between the types of cast irons. All cast irons contain SiC which is very
abrasive for the tool.
Figure 22. Workpiece material groups [44].
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Toolox® 44
The first workpiece material used in this research is Toolox® 44 provided by the company SSAB.
Toolox® 44 is low-alloyed steel because its alloying elements are less than 5% in concentration,
around 3% indeed. (Table 7).
Toolox® is based on low-carbon concept, which provides low carbide concentration. The
inclusions (carbides in this case) make the steel difficult to machine. This is the reason why Toolox®
44 is easy to machine despite its hardness, and it has good stability during machining [45].
This material is delivered quenched and tempered at a minimum temperature of 590ºC. Toolox®
is not supposed to have more heat treatments, which could avoid expensive and risky heat
treatments. Toolox® is produced to rigorous quality standards, its potent mechanical properties are
measured and guaranteed [46]. The mechanical properties of this steel are summarized in Table 8.
Element C (%) Si (%) Mn (%) P (%) S (%) Cr (%) Mo (%) V (%) Ni (%)
% Wt. 0,32 0,6-1,1 0,8 max 0,001 max 0,003 1,35 0,8 0,14 max 1
Table 8. Mechanical and phyical properties of Toolox® 44 [46].
Mechanical properties at 20 ºC Physical properties at 20 ºC
Tensile strength (Rm) 1450 MPa Heat conductivity 34 W/mK
Yield strength Rp02 1300 MPa Thermal expansion coefficient 13,5 10-6/K
Elongation Ap 13 %
Compressive yield strength 1250 MPa
Impact toughness 30J
Hardness 45 HRC
Regarding to these properties, Toolox® has high toughness compared to other steels of similar
hardness (two or three times tougher). This high toughness ensures longer tool life and better
machinability [45]. Toolox® 44 is suitable for plastic moulding, rubber moulding and machine
components.
Department of Production Engineering at KTH have valuable experience in machining this pre-
hardened steel. Daghini and Nicolescu [47] have investigated the influence of inserts coating and
substrate on Toolox® 44 turning process. Tool life, tool wear, chips morphology and temperature
were measured using seven types of cutting inserts and different combinations of two coatings and
four substrates.
Table 7. Chemical composition Toolox 44 [46].
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Grey cast iron (Scania Case study)
The second material that is being tested is a Grey Cast Iron. This material is widely used in
automotive industry because it has very good antivibration properties. The chemical composition
of the material is shown in Table 9.
Table 9. Chemical composition of grey cast iron.
A typical chemical composition to obtain a graphitic microstructure is 2.5 to 4.0% carbon and 1 to
3% silicon by weight. Graphite may occupy 6 to 10% of the volume of grey iron. The presence of
graphite flakes makes the Grey Iron easily machinable as they tend to crack easily across the
graphite flakes. Grey iron also has very good damping capacity and hence it is often used as the
base for machine tool mountings.
The machinability of the grey cast iron is affected by variation in the surface composition, such as
free ferrite residues, which affects directly to the cutting process. The ferrite generates harder zones
in the metal, located randomly, and the graphite instead generates softer areas. This variations in
hardness could influence in the machinability of grey cast iron. In the tested material, to ensure its
machinability, the concentration of ferrite must be below 5%. The microstructure of it and the
hardness, which also affects highly to the machining behaviour are shown in Table 10.
Table 10. Hardness and microstructure of grey cast iron.
Element C (%) Si (%) Mn (%) P (%) S (%) Cr (%)
% Wt. 3-3,5 2 0,6-1 0,4-0,8 0,12 0,4-0,7
Hardness (HB) Microstructure
240-290
Ferrite<5%
Cementite <1%
Graphite (flakes) >90%
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3.2.3 Tooling system
Since in this project two different materials are being tested, also two tooling systems are necessary.
Toolox® 44
The tooling system chosen for this project is provided by the company Mircona AB, cutting inserts
and tool holder. Table 11 shows the ISO designation of these inserts. These cutting inserts are
designed for medium roughing to finishing of all types of steel and cast iron.
Table 11. Geometrical properties of the carbide inserts.
Regarding to the material, chosen inserts are cemented carbide inserts, with three coatings, coated
by the method of CVD (Chemical Vapour Deposition). Coated cemented carbides represent 80 to
90 % of the total of the cutting inserts [48]. These inserts are widely used because they give a good
combination of toughness and tool wear resistant.
The coatings are TIN, Al2O3 and TiCN. CVD coating process is more recommended for inserts
for turning, milling or drilling steels or grey-cast irons. The typical thickness of this type of coatings
is between 9 to 20 µm. The layers are generated by chemical reactions at temperatures between
700ºC to 1050ºC. PVD (Physical Vapour Deposition) process allows obtaining layers of 2-3 µm.
These coatings are used mainly in cutting difficult to machine materials, such as superalloys or
titanium alloys [49]. The benefits of the CVD-coatings types are summarized in Table 12. These
coatings are continuously being improved, trying to optimize the toughness, adhesion and wear
resistance.
Code DCMT 11 T3 08-PM7
D 55 º (Rhombic)
C Clearance angle 7º
M Tolerances
T Type of clamping
11 Insert size, d=9.52 mm
T3 Insert thickness, 3.18 mm
0.8 Corner radius 0,8mm
PM Medium pass
Figure 23. Cemented carbide inserts, DCMT 11 T3 08-PM7.
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Table 12. Benefits of insert coatings [54].
On the other hand, for the present study a specially designed tool holder is used. This MQL holder,
also designed by Mircona AB, allows to apply the lubricant with precision in the cutting zone. This
tool holder applies the oil internally [50]. Figure 24 shows the design of the tool holder utilized.
TiN coatings TiC Coatings Al203 Coatings
• Excellent build-up edge resistance
• Excellent wear resistance
• Excellent crater resistance
• Excellent on gummy materials • Effective at medium speeds
• Effective at high speeds and high heat conditions
• Excellent for threading and cut off operations
• Excellent on abrasive materials
• Makes it easy to identify what insert corners have been used
• Effective at lower speeds
Figure 25. Tool holder for MQL, Mircona AB..
Figure 24. Tool holder design for MQL, Mircona AB [8].
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Selected holder has two outlets to supply the oil. On top, 1 mm diameter hole, to supply oil to the
crater, and on the front relief, 1.5 mm one, to apply the oil in the cutting edge. The connection
between in hose and the tool holder in made with a tread of 1/8”, and a cylindrical hole of 5 mm
of diameter. To ensure that the system works properly in particularly important to seal all the
connections, to avoid oil and air leakage. It is also important to ensure that the oil is reaching the
cutting zone. For this purpose, the amount of oil supplied can be controlled.
Grey cast iron (Scania case study)
For the second part of the project, Scania case study, it was necessary to use a new tooling system.
This tooling system was provided directly by Scania, to reproduce the same process as it is being
carried out at their plant.
Cutting inserts used are oxide ceramics, a standard cutting material for turning cast iron and alloyed
cast iron with high standards for wear resistance [51]. These inserts were provided by Ceramtec
AB. Oxide ceramics are aluminium oxide based (Al2O3) with added zirconia (ZrO2) for crack
inhibition. The composition makes cutting inserts very resistance to tool wear but lacks of thermal
shock resistance [48].
Table 13. Geometrical properties of the ceramic inserts.
The tool holder suitable for these inserts is provided by Sandvik Coromant. This tool holder is
designed for machining under flood cooling conditions, or dry cutting, but it is not suitable for
MQL technology. Sandvik Coromant is already working with this technology, so they can
customize tool holders for MQL. But for running this second experimental part, instead of using
a fixed tool holder designed by Sandvik Coromant, a system designed at KTH-IIP was chosen.
Code DNMX 15 T07 12
D 55 º (Rhombic)
N Clearance angle 0º
M Tolerances
X Type of clamping
15 Insert size, d=12.7 mm
T07 Insert thickness, 7.94 mm
12 Corner radius 1.2mm
Figure 26. Oxide ceramic inserts, DNMX 15 T07 12.
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This new design allows to control the direction of the oil flow. The design has two nozzles. These
nozzles are made of 2 mm of internal diameter copper hoses. The decision of choosing the copper
is because it is flexible enough to be adjusted, but on the other hand it is stiff and resistant. The
tool holder with the design attached is shown in Figure 27.
One of the nozzles supplies the oil to the flank and the cutting edge, and the other directly to the
nose. In results and analysis section, the influence of the control of the direction of the oil flow
will be explained in detail.
The second challenge that appears while designing the experimental set-up for Scania case study
was the clamping. The workpiece material provided by Scania comes in the form of cylinders,
which poses a difficulty when clamping. The pressure that the clampers of the turning machine.
The pressure that the clampers of the chuck exert in the cylinders can break them. For this purpose,
two solid cylinders or bars were machined. The first one is made of aluminium alloy, and it is
introduced inside the cylinder, in the side of the chunk, to clamp it without damaging it. The
reason for choosing this material is that it is tough enough to withstand the pressure of the
clampers. The second one, machined in steel, is designed to fix the tailstock. Figure 28 shows the
clamping system used for the experimental work.
Workpiece rotation
Cylinder 1
Cylinder 2
Clampers
Figure 28. Clamping system for Scania Set-up.
Figure 27. MQL external supplier designed at KTH-IIP.
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3.3 Description of the MQL system
MQL is known a lubrication technique in which a small amount of oil is applied in form of mist
directly into the cutting zone. Actually, as it is explained in the state of art, this technique is
worldwide used in the metal working industry and it effectiveness is already proved.
There are many alternatives of MQL boosters available in the market, but the Swedish company
Accu-Svenska AB is a leader in this type of technology, offering in their catalogue high
performance MQL boosters, such as ECOLUBRIC® booster, that is the one chosen for this
project. The booster system provided by Accu-Svenska AB transports the lubricant-air mixture
through the machine tool, in order to reach the cutting edge of the tool [52].
The oil chosen for performing the first experiments is ECOLUBRIC® E200L, also provided by
Accu-Svenska AB. This lubricant is an economic and environment-friendly alternative for friction
reduction in industry. The lubricant is directly extracted from plants; this oil is pure vegetable-based
lubricant without any chemical modification. The properties of ECOLUBRIC® E200L are shown
in Table 14 [53].
Table 14. General properties of Ecolubric E200L [11].
Properties Description
Chemical description
Cold-pressed rapeseed oil without additives.
Health hazard The product is not harmful to health and involves no special hazards for humans or the environment
Appearance Liquid
Colour Yellowish
Smell Neutral
Melting point -18°C
Flash point 325°C
Density (20°C) 0,92g/cm3
Viscosity (20°C) 70 cP
Figure 29. Ecolubric MQL booster and Ecolubric E200L vegetable oil.
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Figure 30. MQL booster drawing and components list.
Figure 30 shows the schematic of the MQL Ecolubric booster system used for this research project. All the components are presented in the table in the right of the image.
1 oil and air (mist) outlet
2 oil refill
3 oil gauge
4 oil deposit
5 electric switch
6 air cleaner
7 handle
8 pressure gauge
9 electric plug
10 air connection
11 electric switch
12 electric plug
13 solenoid
14 mounting plate
15 oil pump
16 terminal
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3.4 Collection of the machining variables
The equipment available in the KTH-IIP laboratory used for this project will be described in the
following section.
3.4.1 Measurement of tool wear mechanisms and tool life
The wear in the cutting insert appears due to the friction between the tool and the workpiece. To
measure the evolution of the wear, optical microscope NIKON Optiphot 150 is used. The flank
wear and the crater wear are being measured.
DeltaPix Insight software has the option to calibrate the different magnifications and to create a
ruler and a scale to quantify the wear. Also, surfaces can be measured. The capture of the images
of the flank and the crater is done with a Delta Pix Invenio II microscope camera and analysed
with the DeltaPix InsIght proed by DeltaPix.
Figure 32. DeltaPix Insigtht software.
Figure 31. Microscope NIKON Optiphot 150.
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Wear on cutting edges
To understand the cutting process properly it is particularly important to study the different wear
mechanisms that occur in the cutting inserts and its causes.
a. Flank wear
Flank wear is the most common type and most desirable and predictive. It could cause bad surface
finish and bad tolerances in the workpiece. The variable that affects more to the presence of this
wear is the high cutting speed. This type of wear can be measured and quantified. The maximum
flank wear can be used as a limit for the end of the tool life. Flank wear occurs due to abrasion,
caused by hard constituents in the workpiece material [54].
b. Crater wear
This type of wear is located in the rake side of the cutting insert. It is usually caused by chemical
reactions between the workpiece material and the insert. Extreme crater wear could cause insert
breakage. It can be reduced decreasing the relation between cutting speed and feed (vc/fn). It is due
to chemical reaction between the workpiece material and the cutting tool and is amplified by cutting
speed [54].
c. Built-up edge
Material from the workpiece is welded into the cutting insert due to the high pressure. It is very
common in machining sticky and soft materials such as low carbon steel or aluminium. Low
machining speed increases the possibility to appear build-up edge. It occurs due to adhesion
processes.
d. Notch wear
Notch wear it is characterized by excessive damage localized in both the rake and the flank. The
damage appears at the depth of cut line. It usually appears in machining stainless steels and HRSA.
Cermets or Al2O3 coated inserts help to reduce this type of wear. It is caused by adhesion, pressure
welding of chips, and a deformation hardened surface [54].
e. Plastic deformation
Plastic deformation appears when the tool material is softened. High cutting temperatures are the
main cause. Harder grades or thicker coatings might be a solution. It could lead to premature chip
breakage.
f. Thermal cracks
Thermal cracks appear when there is fast variation in temperature. These cracks are perpendicular
to the cutting edge. This type of wear is related to interrupted cuts, and commonly appears in
milling operation. It can be avoided by using a tougher grade or controlling the cooling, using
abundant coolant or none at all.
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g. Insert breakage
It is usually the result of an overload mechanical tensile stresses. But it can also be due to many
other reasons such as wrong cutting parameters, inclusions in the workpiece material, vibrations,
built-up edge or excessive wear.
a b
c d
e f
g
Figure 33. Types of tool wear (a. Flank wear, b. Crater wear, c. Built-up edge, d. Notch wear, e. Plastic deformation, f. Thermal cracks, g.
Edge breakage) [55].
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Machining processes
The flank tool wear was measured in the machining experiments fixing the cutting time steps. Two
different procedures were follow for the two experimental set-ups. The maximum values of the
flank tool wear were measured after these defined cutting steps.
It was estimated a tool life of 15 minutes for the experiments with Toolox® 44 hardened steel. The
time of each cutting step was 90 seconds, so the flank wear was observed and measured under the
microscope every 90 seconds of continuous machining. In order to achieve this 90 seconds, the
cutting length has been adjusted for the different diameters of the round steel bar that was available.
On the other hand, the machining process for the grey cast iron was partially different. In this case,
since the objective was to compare the obtained results with real machining parts an equivalent test
specimen was defined.
Table 15. Test specimen equivalent cutting parameters.
Cutting paramenters 1 test specimen
Feed (mm/r) 0,3
Depth of cut (mm) 0,5
Cutting speed (m/min) 520
Spindle speed (rpm) 1210-1260
MRR (cm3/min) 78
Length of cut (mm) 50
Time (s) 7,9
Material removed (cm3) 10,3
0,5mm x 50mm
Equivalent to 1 test specimen
Figure 34. Cutting profile for grey cast iron machining experiments.
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3.4.2 Measurement of Temperature in the cutting zone
FLIR SC 640 supplies a combination of infrared and visible spectrum images of superior quality
and temperature measurement accuracy [55]. The purpose of the Infrared Camera in the Project is
to measure the evolution of the temperature in the cutting zone. The specification of the camera
FLIR SC 640 is shown in the Table 16.
Table 16. General specification on thermal infrared camera FLIR SC 640 [12].
The thermal camera FLIR SC 640 needs a software to analyse and collect the data. The software is
called ThermaCAM Researcher Professional. This software allows to extract temperature data in
and IR images and videos. Afterwards, to analyse and extract conclusions from the temperature
values, Matlab software is being utilized to filter and plot the results.
Specifications Thermal camera FLIR SC 640
Field of View (FOV) / minimum focus distance
24° x 18° / 0.3 m – 12° x 9° / 1.2 m – 45° x 34° / 0.2 m as an option
Spatial resolution 0.65 mrad for 24°lens – 0.33 mrad for 12° lens – 1.3 mrad for 45° lens
Thermal sensitivity 30 mK at 30°C
Electronic zoom 1-8x continuous including pan function
Electric and manual focus Auto and manual
Accuracy ± 2°C or ± 2% of reading
Temperature range -40°C to +1500°C (optional up to +2000°C)
Figure 35. Thermal infrared camera FLIR SC 640 [55].
KTH Royal Institute of Technology Experimental methodology
Marta García Tierno 45 of 88
3.4.3 Measurement of the Surface Roughness
The surface roughness tester chosen for conducting the study is the Mitutoyo SJ-210 [56]. The
most significant value measured and analysed is Ra, arithmetical mean of the surface profile. The
surface roughness was measured three times in each workpiece after machining, and only the mean
values are presented in this report. The roughness standard selected was JIS’01.
Table 17. Specifications of Surface Roughness Tester Mitutoyo SJ-210 [56].
The surface roughness was measured for the Scania study case. In this case the workpieces were
removed every 21-equivalent test specimen, so the surface roughness was measured for different
machining steps.
Model Mitutoyo SJ210
Measuring range 17.5 mm
Measuring speed 0.25/0.5/0.75 mm/s Returning:1mm/s
Measuring force 4mN
Standards JIS'82/JIS'94/JIS'01/ISO'97/ANSI/VDA
Filters Gaussian, 2CR75, PC75
Sampling length 0.008/ 0.25/ 0.8/ 2.5 mm
Stylus profile 5 µm/ 90°
Figure 36. ThermaCAM Researcher Professional 2.10. Software.
KTH Royal Institute of Technology Experimental methodology
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For the experiments for the pre-hardened steel the material came in the size of round bars of 140
mm of diameter and 2 m length. These bars were cut into smaller bars of 0.5 m length. The same
bar was utilized for several experiments, so the surface roughness could not be measured.
Software provided by Mitutoyo was used to analyze the measured surface roughness results. The
selected standard for this purpose is JIS 2001. In Table 18 the specifications of selected standard
are shown.
Table 18. Surface roughness JIS 2001 standard parameters.
JIS 2001 standard gives three surface roughness values:
• Ra
• Rz
• Rq
Arithmetical mean surface roughness Ra is obtained from the following formula, when the surface
roughness is expressed by y=f(x), taking x-axis to the mean line direction and Y-axis the vertical
value of the surface roughness curve in a sample reference length “l”.
𝑅𝑎 =1
𝑙∫ |𝑓(𝑥)|𝑑𝑥𝑙
0
Standard JIS 2001
Profil R
λs 2.5 µm
N 5
Cut-Off 0.8 mm
Filter GAUSS
Figure 37. Mitutoyo SJ-210 Surface Roughness Tester.
KTH Royal Institute of Technology Experimental methodology
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Following JIS 2001 standard Rz value is ten points mean roughness. This value is obtained from
the total of the mean value of each distance between the mean line and 5 peaks, Yp, from the
highest one, and the mean value of each distance between the mean line and the 5 valleys, Yv, from
the lowest one, of the roughness curve in a sample reference length “l”.
𝑅𝑧 =∑ 𝑌𝑝𝑖 + ∑ 𝑌𝑣𝑖5
𝑖=15𝑖=1
5
Root mean square surface roughness, Rq, is referred to as the sum of the squares of the individual
heights and depths from the mean line in a sample reference length “l”.
𝑅𝑞 = √1
𝑙∫ 𝑓2(𝑥)𝑑𝑥𝑙
0
Machining is usually the manufacturing process that determines the final geometry and dimension
and surface finish. The surface roughness of a machined piece is determined by geometric factors,
work material factors and vibration and machine tool factors. Within geometric factors there are
different parameters that determined the surface finish of a machined part [57]. They include:
• Type of machining operations.
• Cutting tool geometry, most importantly nose radius.
• Feed
Ra
Rz
Rq
Figure 38. Surface roughness profile and values, Ra, Rz and Rq for JIS 2001 standard [57]
KTH Royal Institute of Technology Experimental methodology
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Type of machining operation refers to the process that generates the surface, turning in this case.
Tool geometry combined with feed from the surface geometry. The effects of the feed and
geometry of the cutting insert in surface finish can be seen in Figure 39.
The effect of the nose radius can be seen in Figure 39. (a). Keeping the feed constant, a larger nose
radius causes less pronounced feed marks, thus leading to a better surface roughness. If two feeds
are compared with the same nose radius, larger feed rate increase the separation between feed
marks, leading to an increase in the surface roughness Figure 39 (b). Higher end cutting edge angle
(ECEA) will also result in a higher surface roughness value Figure 39 (c).
The effects of nose radius and feed can be combined in an equation to predict the ideal average
roughness of a surface machined by a single point tool. This equation will be use in this project to
compare the theoretical value with the experimental one.
𝑅𝑎𝑖 =𝑓𝑛
2
32𝑁𝑅
Where Rai=theoretical arithmetic average surface roughness, (mm), fn=feed (mm/rev) and NR= nose radius
on the tool point (mm) [57].
Figure 39. Effect of geometric factors in determining the theoretical finish on a work surface for single-point tools: (a) effect of nose radius, (b) effect of
feed, and (c) effect of end cutting-edge angle [57].
KTH Royal Institute of Technology Results and Discussion: Toolox® 44
Marta García Tierno 49 of 88
4 RESULTS AND DISCUSSION: TOOLOX® 44
The results and discussion section show the experimental values obtained after machining under
different cooling-lubrication techniques at KTH-IIP laboratory. As it was explained in the
experimental methodology section, while Toolox® 44 pre-hardened steel was machined, internal
MQL is being tested. The comparison was made under different conditions that will be explained
in detail in this chapter. At the beginning of the experimental work some troubles were found with
the experimental set-up that did not allow to extract any conclusion from the collected values.
After solving these problems, valuable results were obtained, and the performance revealed
encouraging potential of MQL technology for turning Toolox® 44. In order to show the potential
of MQL three machining variables are going to be measured: tool wear, temperature and tool life.
Chips shapes and colour is also analysed.
To analyse the tool wear properly the subsequent procedure was followed:
• Flank and crater picture were captured. The flank wear was measured using the software
mentioned in the experimental methodology section.
• Chips were collected for each cooling lubricating technique. The chips were analysed
visually, paying attention to the colour and the shape.
• Every insert was utilized twice, following the recommendations of the producer.
• The experiments under each cooling-lubrication strategy were repeated three times.
The most significant wear type that appears in coated carbide inserts is the flank wear. The criteria
selected to declare the end of the tool life is 0.3 mm of wear in the flank. During the experimental
work, other types of wear also appear and will be explained in this section.
4.1 Preliminary results
First experiments were carried out using various cooling strategies at a cutting speed of 110 m/min,
feed of 0.2 mm/rev and depth of cut of 0.5 mm, following the recommendations suggested for
the cutting inserts. The cutting parameters are shown in Table 19. The flow rate used for these
experiments was between 2 and 5 mL/h and 4 bars of air pressure. As it is explained in the previous
section, the machining time is fixed for these experiments, in this case 48 seconds of continuous
machining for each step.
Table 19. Cutting parameters, first experiments Toolox® 44.
Cutting parameters Value
Cutting speed 110 m/min
Feed 0.2 mm/rev
Depth of cut 0.5 mm
Machining time (1 step) 48 s
Flow rate 2-5 mL/h
Air pressure 4 bars
KTH Royal Institute of Technology Results and Discussion: Toolox® 44
Marta García Tierno 50 of 88
Figure 40 shows the evolution of the flank wear observed for dry machining in the steel that was
available in the laboratory. This material came from an old batch with an uncertain origin. The
repeatability in the dry machining results was quite high, after three experiments three tool lives
were recorded, 11.2, 10.4 and 12.8 mins. After these dry experiments, different lubrication
techniques started to be tested in the same Toolox® 44 round bar.
As soon as the second experimental work started the drawbacks begin to appear. The experiments
were repeated at least three times for each lubrication technique, but the dispersion that appeared
in the results was too high. Figure 41 shows some examples of tool wear evolution for the different
tested techniques. Some experimental work with a Nanofluid with wt. 1% of MoS2 nanoparticles
was also tried (MQL+NF in the graph). But as it is presented in Figure 41, the results were
unconcluded, because repeatability could not be extracted from the experimental outcomes.
After these troubling outcomes, the reasons to explain them began to be an objective. The first
idea was that the problem resided in the tooling system, that it was not appropriated for the material
and the selected cutting parameters. Mircona engineers were contacted and they came to IIP-KTH
laboratory to analyse the cutting parameters. They concluded that the cutting variables were
adequate for the experimental work. Secondly, the material was studied, looking for an explanation.
The hardness was measured, extracting the conclusion that there was a significant difference from
the outside of the piece to the core. This was the reason why new Toolox 44 round bar was bought,
4 m length and 160 mm of diameter. Once the new bar arrived, the second round of experiments
started. These results are presented in the following section.
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0 2 4 6 8 10 12
Fla
nk
wear
(mm
)
Machining time (min)
Dry 1
Dry 2
Dry 3
End of tool life
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0 5 10 15 20
To
ol
wear
(mm
)
Machining time (mm)
End of tool life
MQL+Veg oil
Dry
MQL + NF
Figure 40. Flank wear vs. Machining time, first experiments Toolox® 44, dry machining.
Figure 41. Flank wear vs. Machining time, first unsuccessful experiments Toolox® 44, three lubrication techniques.
KTH Royal Institute of Technology Results and Discussion: Toolox® 44
Marta García Tierno 51 of 88
4.2 Comparison between different lubrication techniques
Once new hardened steel bar arrived, the second round of experiments started. In this case, the
cutting parameters were selected to cut under extreme conditions, increasing the cutting speed up
to 120 m/min and extending the continuous machining time up to 100 seconds. Two depths of
cut were tested: 0.5 and 1 mm, finding significant differences between them that will be explicated.
The experiments for each cooling-lubricating technique were repeated three times to understand
the process completely and rely in the results. In Table 20 the cutting parameters are presented.
Table 20. Cutting parameters, Toolox 44 experiments.
4.2.1 1 mm of depth of cut
Initially, 1 mm of depth of cut was selected for the experimental work. The reason of selecting
bigger depth is that the design of the chip breaker of the inserts is suitable for this depth of cut, so
shorter chips are obtained. Instead of long continuous chips obtained initially, these chips are 5-10
mm long. But after 360 seconds of machining, the chips became long and continuous. The crater
was observed under the microscope and as Figure 42 shows, the chip breaker was worn away. On
the left side of the picture the crater is shown after one step and on the right after 4 steps of dry
machining, that it stopped working.
Cutting parameters Value
Cutting speed 120 m/min
Feed 0.2 mm/rev
Depth of cut 0.5/1 mm
Machining time (1 step) 90-100 s
Flow rate 5-10 mL/h
Air pressure 4 bars
Figure 42. Damaged and broken chip breaker, crater images x10, 1mm of depth of cut, dry machining.
Chip breaker
Damage in the
chip breaker
KTH Royal Institute of Technology Results and Discussion: Toolox® 44
Marta García Tierno 52 of 88
On the other hand, when the depth of the cut is 0.5 mm, the chips are long and continuous, which
means that the chip breaker is not working properly. Figure 43 shows two images of the crater for
0,5 mm of depth of cut machining under MQL with vegetable oil, after 90 seconds of machining
and after 360 seconds. The wear in the chip breaker is irrelevant, which means that it is not working
properly. This conclusion can also be extracted from the fact that the chips are long and continuous
from the first machining step.
The problem of continuous blue long chips is common in machining high tensile strength material.
Chips must be controlled in order to avoid future problems that affect adversely the machining
process in the following ways: spoiling the cutting edge, raising temperature, poor surface finish or
hazardous to machine operator.
Figure 44 shows the plots of the flank wear under the mentioned cutting conditions for two cooling
strategies: MQL using vegetable oil (Ecolubric E200L) and dry machining. The observation shows
that MQL performance is relatively better than dry machining, obtaining smaller flank wear values
for all machining steps. Each tool life experiment was repeated three times, and these results are
plotted in the graph.
0
0,05
0,1
0,15
0,2
0,25
0,3
0 5 10 15 20
Fla
nk
wear
(mm
)
Machining time (mins)
MQL(Vegetableoil, Ecolubric200L)EndOfToolLife
Dry
Figure 43. Crater images x10, 0,5 mm of depth of cut.
Figure 44. Flank wear vs. machining time for dry and MQL, 1 mm of depth of cut, Toolox 44.
KTH Royal Institute of Technology Results and Discussion: Toolox® 44
Marta García Tierno 53 of 88
In terms of tool life an average improvement of 21.4% was found comparing MQL with dry
machining. Figure 45 shows the different tool lives values for three repeated experiments.
Numerical results are summarized in Table 23.
While the tool wear and tool life were measured the chips were collected and analysed. In the case
of dry machining, the colour of the chips was completely burnt blue. On the other hand, the MQL
chips were purple, between gold and blue. The expected colour of the chips machined under MQL
was completely light golden. This colour means that the friction is being reduced, and consequently
the temperature is also lower. The first conclusion extracted from this colour of the chips was that
the oil was not reaching properly the cutting zone. The difference in the colour of the chips
between dry and MQL was due to the cooling effect of the generated mist. In order to separate the
two functions of the cutting fluids, cooling and lubricating, only pressured air was introduced
through the system. The MQL booster gives the option to reduce the oil delivered to the cutting
zone. Figure 46 shows the flank wear for machining with compressed air compared also with dry
and MQL cooling strategies.
Tool life (min) MQL Dry
Experiment 1 18.33 15
Experiment 2 20 16.67
Experiment 3 18.33 15
Average 18.89 15.56
Improvement 21.4%
Table 21. Tool life, dry and MQL, 1 mm, Toolox 44.
Figure 45. Comparison of tool life, dry and MQL, 1 mm of depth of cut, Toolox 44.
0
5
10
15
20
25T
oo
l li
fe (
min
s)
MQL DRY
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,00 5,00 10,00 15,00 20,00
To
ol
wear
(mm
)
Machining time (mins)
MQL
Dry
Air
End of tool life
Figure 46. Flank wear measurement, 1 mm of depth of cut, dry,MQL with vegetable oil and
compressed air.
KTH Royal Institute of Technology Results and Discussion: Toolox® 44
Marta García Tierno 54 of 88
When oil is provided to the tool, the flank wear should be apparently smaller due to the friction
reduction. In this case the relative difference was below 15% for all steps. Figure 46 shows flank
and crater images after 8 steps of machining, 13.3 mins for three cooling techniques. The flank
wear curve was built based on these pictures of the inserts taken under the microscope. Flank wear
measurement, 1 mm of depth of cut, dry and MQL with vegetable oil.
The chips were also analysed. There was not any difference between the chips after machining with
MQL technology and the ones obtained machining only with compressed air. The colour of both
chips was between blue and golden, purplish.
Cutting temperature was also measured for the first four machining steps. The reduction between
machining under dry and MQL with vegetable oil is significant, up to 30% of relative reduction for
all the machining steps. Figure 48 (a) shows the average temperature for each machining step.
Furthermore, Figure 48 (b) shows the evolution of the temperature for three cooling techniques in
one step of 90 seconds.
(a)
(b)
(c)
Figure 47. Flank and Crater images x10, 13,3 mins of machining, 1 mm, Toolox 44 (a)Dry machining (b)Compressed air (c)MQL.
KTH Royal Institute of Technology Results and Discussion: Toolox® 44
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Reduction up to 30 ºC can be observe between MQL and dry machining. The relative difference
between MQL and air in average temperature is less than 5%, as it can be observed in Figure 48
(a). In the case of one machining step, Figure 48 (b), the maximum difference in temperature is 4
ºC. The temperature results in addition to the analysis of the colour of the chips could lead to the
conclusion that the oil mist machining under this set-up is not reaching properly the cutting edge.
This is the main reason to move to smaller depth of cut, to ensure that the oil reaches the cutting
point properly.
On the other hand, other conclusions could be extracted from Figure 48 (b) and (c). Firstly, graph
(b) shows the evolution of temperature during 90 seconds of machining. The curve for MQL and
compressed air are flat, and the increase of temperature between the initial and the final time is
only 4ºC. Instead, in the dry machining temperature curve there is a significant slope. The increase
of temperature is 22ºC in 90 seconds. It can also be observed that the temperature in dry is 15ºC
higher than MQL or compressed air when the machining started. Finally, in graph (c) the cooling
down zone is plotted. This zone represents the temperature that remains in the workpiece after
machining. The difference between the cooling techniques is significant, up to 18ºC when dry
machining and MQL are compared.
40
60
80
100
120
0 1,5 3 4,5 6
Tem
pera
ture
(ºC
)
Machining time (mins)
Dry MQL Air(a)
(b)
(c)
Figure 48. Temperature graphs 1 mm, dry, air and MQL, Toolox 44(a)Average temperature vs. machining time (b)Evolution of T during 90 s of
machining (c) Evolution of T last 15 s of one machining step.
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Figure 49 shows an example of an Infrared Image captured with ThermaCam FLIR SC640. The
maximum temperature of the area inside the circle, that includes the cutting point, is represented
in the previous graphs. There are some high values that were removed in order to obtain a reliable
average. Matlab code utilized for this purpose can be found in Appendix A.
Figure 49. Instantaneous Temperatures IR image, compressed air, 1 mm, Toolox 44.
KTH Royal Institute of Technology Results and Discussion: Toolox® 44
Marta García Tierno 57 of 88
4.2.2 0.5 mm of depth of cut
The main conclusion extracted from 1 mm of depth of cut experimental work was that, even if the
chip breaker was working and the chips were under control, the mist was not reaching properly
the cutting point. These results motivated the decision to move to smaller depth of cut and 0,5
mm was chosen. The other cutting parameters were kept constant. The parameters are shown in
Table 20.
Firstly, chips were collected and analysed repeating the same machining process: measuring the
tool wear after 90 seconds of continuous machining under three different techniques: MQL with
vegetable oil, compressed air and dry machining. The chips were different for three cases from the
first machining step. The chips are continuous and long in all the experiments, due to the selected
cutting depth and the properties of the workpiece material. Under these cutting conditions the
design of the chip breaker of the cutting inserts is not the most suitable option. The chips are
shown in Figure 50.
Chips obtained from dry machining are completely blue, burnt and washer type or helical. Blue
intense in colour indicates high chip tool interface temperature. When oil is applied using MQL
booster, the chips are light golden and completely tubular. The chips obtained machining with
compressed air are a mix between the two previous chips. They are blue-golden, purplish, and
helical. Chips obtained machining under air and MQL and 1 mm of depth of cut are very similar
to these chips. Light golden chips indicate lower temperature, due to the reduction in the friction
that the oil is generating. The mentioned indications lead us to think that the oil was reaching the
cutting zone properly machining 0.5 mm of depth of cut.
Secondly, the tool wear curves were built. A tool life of 15 minutes was estimated from previous
experiment, so initially 10 steps of 90 seconds of continuous cutting were defined for each
lubrication technique. The results of the flank wear are plotted in Figure 51.
Figure 50. Chips samples for Dry, Compressed air and MQL, 0.5 mm, Toolox 44.
Dry
Air
MQL
KTH Royal Institute of Technology Results and Discussion: Toolox® 44
Marta García Tierno 58 of 88
Figure 52 shows the flank images after 15 of machining, last measured step, for three studied
lubrication techniques. The only significant wear that appears in under these cutting conditions is
flank wear, caused by abrasion processes. There are not adhesion or chemical wear found in the
microscopic images. The end of the tool life is set to flank wear of 0.3 mm.
Some conclusions can be extracted from Figure 51. There is a systematic reduction in flank wear
when MQL technique is used. The biggest difference comes after 15 minutes of machining, up to
100% of improvement when dry and MQL are compared. The cutting inserts are almost broken
for dry machining and cutting with compressed air, obtaining flank wear values close to the 0.3
mm limit.
On the other hand, the cutting inserts used for machining under MQL have an acceptable value of
tool wear after 15 minutes, giving the possibility to continue machining. The results of cutting with
compressed air showed slightly better performance than dry machining during the middle steps,
but in terms of tool life are comparable. This behavior was also found in the previous experiments
when the cutting depth was 1 mm. The air introduced in the cutting zone helps to reduce the
cutting temperature directly but has no affect in the friction. The small improvement in the tool
life is caused by this reduction in temperature. It is particularly important to ensure that the oil is
reaching properly the cutting zone to reduce the friction in the chip tool interface. This leads to
bigger reduction in temperature as well.
1 2 3
0
0,05
0,1
0,15
0,2
0,25
0,3
0 3 6 9 12 15
Fla
nk
wear
(mm
)
Machining time (min)
Dry
Dry
MQL
MQL
Air
Air
3
2
1
Figure 51. Flank wear vs. machining time for dry, air and MQL, 0.5 mm of depth of cut, Toolox 44.
Figure 52. Flank images, 15 mins of machining, 0.5mm of depth of cut, Toolox 44.
KTH Royal Institute of Technology Results and Discussion: Toolox® 44
Marta García Tierno 59 of 88
Finally, temperature was measured for first four cutting steps of 90 seconds. The results are plotted
in Figure 53. New conclusions can be extracted from this graph that demonstrate that the MQL
system is optimized for a cutting depth of 0.5 mm.
Figure 53 shows the average temperature for first four cutting steps and two cutting depths. The
temperature in the cutting zone are significantly lower when air or MQL is applied. An average
relative reduction of 15 % was found. This difference in temperature is appreciable from the first
90 seconds of machining, with a reduction of 10ºC. In contrast, when the cutting depth is 1 mm,
the relative difference in temperature is only 5%, 2ºC after the first machining step. These results
evidence the hypothesis that the oil is reaching the cutting zone and the friction is reduced.
Finally, Table 22 summarizes average temperature values for the three cooling-lubricating strategies
and two cutting depths. The biggest difference appears when MQL with 1 mm and 0.5 mm are
compared, a reduction of 21.2%, compared to the 5.3% of dry and 11% of air.
Table 22. Average temperature values, 0,5 and 1 mm, Toolox 44.
Cooling strategy/ Cutting depth 0,5 mm 1 mm
Dry 98.7ºC 103.9ºC
Air 74.7ºC 82.9ºC
MQL 65.4ºC 79.2ºC
Figure 53. Average temperature vs. machining time, 0,5 and 1 mm, Toolox 44.
40
50
60
70
80
90
100
110
120
0 1,5 3 4,5 6
Tem
pera
ture
(ºC
)
Machining time (min)
Air 0,5mm
Dry 0,5mm
MQL 0,5mm
Air 1mm
Dry 1mm
MQL 1mm
KTH Royal Institute of Technology Results and Discussion: Scania Case Study
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5 RESULTS AND DISCUSSION: SCANIA CASE STUDY
This chapter presents the results and the main outcomes from the experimental work done for
Scania Case Study. As it was explained in Experimental Methodology chapter, the workpiece
material was provided directly by Scania. Cutting inserts and tool holders were also supplied by
Scania. Cutting parameters were selected in collaboration with the company to try to reproduce the
process as close as possible. The experimental set-up was revised by Scania employees to ensure
that the machining process was correct.
Table 23 summarizes the cutting parameters for Scania Case Study. These parameters could not be
modified even if the results could be optimized. The values are kept constant to reproduce the
process that it is carried out at Scania in Södertälje. One test specimen equivalent is defined, to
compare with the number Södertälje of production provided by Scania with one cutting insert. 120
test specimens are machined in with one side of one cutting inserts. The cutting tools are indexable
inserts, meaning that they can be rotated or flipped, so each cutting insert will be used four times.
Table 23. Cutting parameters, Scania Case Study.
To summarize, the subsequent procedure was followed to analyse the machining process:
• Flank and crater picture were captured. The flank wear was measured using the software
mentioned in the experimental methodology section. They were observed after machining
three test specimen equivalent.
• Every insert was utilized four times, following the recommendations of the producer.
• The experiments under each cooling-lubrication strategy were repeated two times. In this
case experiments cannot be replicated three times due to the limitation in material amount.
Cutting parameters 1 test specimen
Cutting speed 520 m/min
Feed 0.3 mm/rev
Depth of cut 0.5 mm
Spindle speed 1210-1260 rpm
Machining time (1 specimen) 7.9s
Flow rate 5-10 mL/h
Air pressure 4 bars
KTH Royal Institute of Technology Results and Discussion: Scania Case Study
Marta García Tierno 61 of 88
5.1 Comparison between different lubrication techniques
Three different cooling techniques were compared for Scania case study:
• MQL using vegetable oil Ecolubric E200L.
• MQL using Nanofluid, Ecolubric E200L as base oil and 0.5% by weight of MoS2.
• Dry machining. Scania, at Södertälje plant, produces the parts that are the focus of this case
study using this technology.
The main objective of these results and discussion part is to compare dry machining technology
with other technologies that could improve the process and increase the productivity. Tool wear,
tool life and temperature are being measured to compare the techniques. Surface roughness is also
used to prove the potential of this new lubrication techniques. Scania has very strict rules in terms
of quality for finished parts. The average surface roughness Ra should be below 2.5 µm for the
finished pieces.
5.1.1 Tool wear and tool life
In Söderltälje, they can machine up to 120 test specimen equivalents without changing or flipping
the cuttings. This value will be used to compare and established as a goal. Used inserts brought
directly from Scania were analysed under the microscope. Figure 54 shows flank and crater images
of a new ceramic insert, and Figure 55 one side of one of the inserts provided by Scania.
Figure 54. Flank and crater images x5, new ceramic insert.
Figure 55. Flank and crater images x5, broken ceramic inserts, Scania sample.
KTH Royal Institute of Technology Results and Discussion: Scania Case Study
Marta García Tierno 62 of 88
Only 2 sides up to the 16 analyzed were completely worn away. In others, a significant wear was
found, up to 155 µm at worst. Table 24 shows the flank wear found in the cutting inserts received
from Scania. It can be observed that in most of the cases the inserts are not completely broken,
only 2 out of 16, 12.5%. But as it will be discussed in next section, the transition from this wear
values to a worn away flank is unpredictable.
Table 24. Flank wear, Scania used inserts, 120 test specimens.
Firstly, dry machining experiments were carried out, repeating the experiments two times. Tool life
results were recorded, obtaining 69 test specimen equivalents in the first experiment and 54 in the
second one. There are many reasons that could explain these difficulties to reproduce real
conditions and to obtain as good results as the ones obtain in Södertälje (120 parts):
• Higher cutting temperature. In the set up at KTH the same cylinder is machining
continuously, machining 7 times, and 0.5 mm depth. The temperature increases in each
machining, although we wait before starting a new machining.
• Clamping system. The clamping system that we are using, as it is explained, consists of two
cylinders, one fixed in the inner part of the cylinder and the other to fix the tail-stock. There
is always a small deviation, a misalignment when the cylinder is clamped, because this
process is done manually.
• Air suppliers. At Scania facilities, air suppliers are used to remove the chips easily. In the
case studied, more sparks appear, since the chips are not being removed properly. This
process could make the insert and the workpiece itself to suffer more.
After dry machining tests, MQL was tested. In this case study two different fluids were applied,
vegetable oil Ecolubric E200L and 0.5% w.t. MoS2 nCLF, with Ecolubric E200L as base oil. But
first, it was important to ensure that the angle of the nozzles designed at IIP-KTH were correctly
aligned to make the oil reach the cutting zone. These first experiments were carried out using only
vegetable oil.
The first MQL experiment gave a tool life of 81 test specimens. Relative increase in tool life of
31% comparing MQL with vegetable oil with dry machining was found. But it was expected to
obtain a better performance in terms of tool life and tool wear due to previous experience, so the
angle of the nozzle was change. The main objective of this change was to ensure that the oil was
reaching properly the cutting edge and the flank, instead of the crater. So finally, one of the nozzles
was orientated to the nose and the other to the flank and cutting edge, as it is shown in Figure 56.
Flank wear (µm) Insert 1 Insert 2 Insert 3 Insert 4
Side 1 89.23 91.5 109.8 86.9
Side 2 Broken 82.4 116.7 96.1
Side 3 Broken 155.6 112,11 105.3
Side 4 82.37 96.1 105.3 103
KTH Royal Institute of Technology Results and Discussion: Scania Case Study
Marta García Tierno 63 of 88
As soon as the nozzle was realigned the results started to improve. Tool life of 150 test specimens
was obtained in the second tool life experiment with MQL and vegetable oil. Figure 57 shows the
evolution of the tool wear for two different nozzles positioning. Also, first dry machining
experiment is plotted. The new value of tool life shows and improvement of 85% and 117%
compared to first nozzle orientation (MQL 1) and first dry machining experiment (Dry 1)
respectively.
In total, 7 tool life experiments were carried out, comparing three cooling-lubricating techniques:
dry machining, MQL with vegetable oil and MQL with NF. Table 25 summarizes the experimental
work and tool life results in terms of number of test specimen and time. The repeatability of the
results of the same technique is high, excluding the first MQL with vegetable oil experiment, as it
was explained recently. The relative difference is 22% in dry machining, 8% in MQL and 13%
machining with NF. This is reasonable because the material utilized for this experimental work is
provided directly by Scania, and its properties and quality are proved and constant for all the test
specimens. Figure 58 shows the flank wear evolution for best results for different cooling
techniques, Dry 1, MQL 3 and NF 2.
Figure 56. Orientation of nozzles, Scania case study tool holder.
Nozzle to the nose
Nozzle to the cutting edge Nose
Cutting edge
0
50
100
150
200
250
300
0 30 60 90 120 150
Fla
nk w
ear
(µm
)
N of test specimen
Dry 1 MQL1 MQL 2
Figure 57. Flank wear vs. N of test specimen, Dry 1, MQL 1 and MQL 2 Scania case study.
KTH Royal Institute of Technology Results and Discussion: Scania Case Study
Marta García Tierno 64 of 88
Table 25. Tool life for different techniques, Scania case study.
It can be observed that there is a main difference in the evolution of the tool wear between different
cooling-lubricating techniques. Machining in dry and applying the NF the tool breakage occurred
suddenly, on the other hand, applying vegetable oil Ecolubric E200L, the breakage occurs due to
extreme flank wear. Figure 59 shows the flank images for the last machining step for three studied
cases. It can be observed that looking to the first two images, dry and NF, that the flank is destroyed
and above the 0.3mm limit. The decision of stopping the machining in MQL was the obtained
results during the turning. When the flank exceeds 0.25 mm, too many sparks appeared, and it was
not advisable to continue the experimental work, so the end of the tool life was declared.
Experiment number Name
Cooling/ Lubricating Technique
N of test specimen
Time (mins)
1 Dry 1
Dry machining
69 9.1
2 Dry 2 54 7.1
3 MQL 1
MQL Ecolubric E200L
81 10.7
4 MQL 2 150 19.8
5 MQL 3 162 21.4
6 NF 1 MQL NF(0,5%wt
MoS2)
114 15.0
7 NF 2 129 17.0
0
50
100
150
200
250
300
0 50 100 150
Fla
mk w
ear
(µm
)
N of test specimen
Dry 1 NF 2 MQL 3
Figure 58. Flank wear vs. N of test specimen, three techniques, Scania case study.
Figure 59. Flank wear images at the end of tool life Dry 1 x10, NF 2 x5, MQL 3 x10, Scania case study.
KTH Royal Institute of Technology Results and Discussion: Scania Case Study
Marta García Tierno 65 of 88
To conclude with tool wear and tool life analysis, Figure 60 summarizes the tool life results for the
three techniques and two rounds of experiments. In terms of flank wear, the wear obtained under
dry machining is slightly higher than MQL and NF. There is a systematic reduction in tool wear
when vegetable oil or NF is applied. But in terms of tool life the best results are for MQL technique
with vegetable oil. There is a relative improvement of 20.4% and 135 % when NF and dry
machining are compared with vegetable oil. There are some reasons that could explain results when
NF is applied, but the main motivation lies in the fact that the particles are not coming out from
the system. The booster itself might be getting partially block due to the concentration of
Nanoparticles and less amount of oil is reaching the cutting zone. This might be the reason why
the results obtained for turning with MQL and NF showed a performance between dry and MQL
with vegetable oil Ecolubric E200L.
5.1.2 Surface roughness
In this case study surface roughness was also measured. This was possible due to the geometry of
the workpiece as it was described previously. The workpiece was removed after machining 21 test
specimens equivalent for dry machining and 15 for MQL with vegetable oil and NF. Every
measurement was repeated three times and the average was calculated. The most significant value
was the arithmetical mean surface roughness Ra (µm). Figure 61 graphs the average surface
roughness for all the measured values.
69
162
114
54
150
129
0
20
40
60
80
100
120
140
160
Dry MQL NF
Tool life
N o
f T
est
Sp
ecim
en
Figure 60. Comparison of tool life, three cooling techniques, Scania case study.
0
1
2
3
4
Aver
age
Ra
(µm
)
Dry 1 Dry 2 MQL 2 MQL 3 NF 1 NF 2Figure 61. Average arithmetical mean surface roughness Ra (µm), Scania case study.
KTH Royal Institute of Technology Results and Discussion: Scania Case Study
Marta García Tierno 66 of 88
The process that is being done at Scania facilities in Södertälje requires a maximum arithmetical
mean surface roughness Ra value of 2.5 µm. The limit of 2.5 µm is plotted in Figure 61 in dots.
Theoretical surface roughness value is calculated for turning with the cutting parameters, obtaining
a value of 2.34 µm. This value is achieved in all the measured steps when oil is introduced, both
vegetable oil and NF. In dry experiments this value is highly exceeded, above 3 µm in all the
measurements taken. This reduction for both cooling techniques compared with dry machining
could be due to the reduction in cutting temperatures. Figure 62 shows 4 surface profile examples,
measured after one of the middles steps of the experimental work:
1. Scania test specimen sample. Ra=2.343 µm.
2. Machining with MQL + NF. Ra=2.308 µm.
3. Machining with MQL + Vegetable oil Ecolubric E200L. Ra=2.202 µm.
4. Dry machining. Ra= 4.122 µm
Figure 62. Surface roughness profile 1. Scania test specimen sample, 2. MQL + NF, 3. MQL +
Vegetable oil, 4. Dry machining.
-20,0
-10,0
0,0
10,0
20,0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0
[µm]
[mm]
-20,0
-10,0
0,0
10,0
20,0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0
[µm]
[mm]
-20,0
-10,0
0,0
10,0
20,0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0
[µm]
[mm]
-20,0
-10,0
0,0
10,0
20,0
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0
[µm]
[mm]
1
2
3
4
KTH Royal Institute of Technology Results and Discussion: Scania Case Study
Marta García Tierno 67 of 88
All the measurements done for three different cooling-lubricating techniques are presented detail
in Appendix C. These values were utilized to calculate the average values of the surface roughness
that are presented in Figure 61. The arithmetical average surface roughness for dry machining in
presented profile is 4.33 µm. These high values of roughness could be justified by the high cutting
temperatures achieved in dry machining. The nose radius of the selected cutting tool is bit enough
(1.2mm) to achieve good surface roughness results, but the high feed (0.3 mm/rev) utilized makes
more difficult to obtain good quality. Temperature, nose radius and feed are the parameters that
affect most in the surface roughness.
5.1.3 Temperature
In Scania Case study temperature around the cutting zone was also measured. It is important to
explain that the temperature was difficult to measure in this experimental set-up. The turning
experiments were done utilizing the second revolver of the machine tool. Due to the geometry of
the tool holder, it was very hard to access to the cutting point with the Thermal Camera. Figure 63
shows the set up. Furthermore, the cutting time of each test specimen is only 7.9 seconds. This
short cutting time does not let the temperature increase, so it is even more problematic to record
the reduction.
Selected tool holder
Revolver 2
Figure 63. Scania set-up image.
Figure 64. Temperature in the cutting zone vs. machining time, Scania case study.
KTH Royal Institute of Technology Results and Discussion: Scania Case Study
Marta García Tierno 68 of 88
Nevertheless, reduction of 8ºC were recorded for one machining step. The temperature plotted in
Figure 64 shows a reduction up to 10ºC after machining one test specimen equivalent. Although,
it is very difficult to extract any significant conclusions from these temperature measurements.
Finally, Figure 65 shows an example of an Infrared Image captured with ThermaCam FLIR SC640
after 7.9 seconds of turning.
29.4ºC
29
28
27
26
25
24.9ºC
Figure 65. Instantaneous Temperature IR image, Scania case study.
KTH Royal Institute of Technology Conclusions and Future Work
Marta García Tierno 69 of 88
6 CONCLUSIONS AND FUTURE WORK
The work presented in this thesis focused on the investigation of the potential of MQL and further
MQL technique improved with oils enhanced with nanoparticles in two different workpiece
materials and set-ups: pre-hardened steel and Scania case study: grey cast iron. This was executed
by performing different turning experiments with both set-ups and proper cutting parameters and
variables. The general conclusions drawn from this research can be summarized in the following
points:
• The overall potential of MQL technology for the selected experimental set-up and cutting
parameters has been proved in terms of quality and tool life. The utilized cutting parameters
tried to reproduce real conditions as close as possible.
• The better performance of MQL with vegetable oil was proved for Toolox® 44 pre-hardened
steel case study. Three cooling-lubricating techniques were compared in this study obtaining
reductions in tool wear up to 50 % (0.5 mm of depth of cut). In terms of tool life an
improvement of 25% was recorded compared to dry machining.
• When cutting temperatures where measured turning pre-hardened steel, reductions of 31% (1
mm) and up to 51% (0.5 mm) were recorded when vegetable oil Ecolubric E200L was applied,
compared to dry machining.
• The study reveals that it is particularly important to ensure that the oil reaches the cutting
point properly. This conclusion was proved when two different cutting depths were compared.
The colour of the chips is a good indicator of the behaviour of the system itself, obtaining
better results in terms of temperature and tool wear when golden chips appeared.
• The designed system for Scania case study gives the opportunity to adjust the direction of the
flow, which helps to ensure that the oils reaches properly the cutting edge.
• In Scania case study three cooling techniques were compared, dry machining, MQL with
vegetable base oil and MQL with NF. The best performance was obtained using vegetable oil,
obtaining a systematic reduction in the tool wear of 25% compared to dry machining. Tool
life of the cutting inserts was increased in 87% and 135% utilizing MQL with NF and MQL
with vegetable oil respectively.
• In terms of quality, surface roughness and cutting temperatures were also improved with the
new cooling-lubricating technology. The experimental work shows improvements of 34% in
surface roughness and reductions up to 15% in cutting temperature. Regarding to the surface
roughness, using any of the two proposed cooling methods (MQL with vegetable and MQL
with NF), the quality standard asked by Scania (2,5 µm) was achieved for every machining
step.
KTH Royal Institute of Technology Conclusions and Future Work
Marta García Tierno 70 of 88
6.1 Recommendations for future work
During the current work, many interrogates have appeared which can be studied further in future
research work. These questions are summarized in the following points:
• In both studied set-ups, vegetable oil MQL and NF MQL can be studied under different
combinations of oil flow rates and air pressures for new cutting speeds, cutting depths and
feed rates.
• In order to understand the cooling-lubricating process properly, tribological properties of
the fluids could be studied at different temperatures and conditions.
• In Scania case study, the results obtained in dry machining are not as good as expected and
compared to the process done at Scania, Södertälje. These difficulties are explained in the
results chapter and can be solved following some of the advices given. The quality of the
results could be enhanced by improving other aspects of the machining process in the IIP-
KTH laboratory.
• The study shows that the cutting temperature highly affects to the machining process. The
MQL system itself is not able to achieve lower temperatures in machining. One improvement
in the booster system could be to cool down the temperature of the mist before being applied
in the cutting zone. The company Accu-Svenska AB is actually working on this project. They
are working on a new system in which they can reduce the temperature of the mist using a
cryogenic close loop.
• The research reveals that it is particularly important to ensure that the oil is reaching the
cutting edge properly. For this purpose, a solution could be to analyse the actual MQL tool
holder and optimize the design of the holes and nozzles. The CFD modelling techniques can
be very useful to design and visualize the oil flow while customising the tool holder. CFD
technology can provide an optimal solution and save cost and time required for prototyping.
• The literature review shows an impressing potential of oil enhanced with nanoparticles.
Further experimental work should be done using Nanotechnology in pre-hardened steel.
This technology reveals several challenges, such as the design of the MQL booster that
should be solved during the execution of the further research. First step of this research
would be ICP-MS (Inductively coupled plasma mass spectrometry) tests. Some samples of
the oil enhanced with nanoparticles would be collected in the cutting zone and will be
analyzed to measure the concentration of Nanoparticles afterwards. These tests would give
information about what is happening with the fluids inside the MQL booster.
• The potential that MQL reveals for this particular process makes interesting to continue with
this study. In order to include this technology in an industrial process, like the one that is
carrying out at Scania, Södertälje, Further study on MQL system design and implementation,
including cost and life cycle analysis.
KTH Royal Institute of Technology References
Marta García Tierno 71 of 88
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KTH Royal Institute of Technology Appendix A. Codes
Marta García Tierno 76 of 88
APPENDIX A. CODES
1. CNC Codes for turning operations
Toolox® 44
Channel 1: File name: MQLTEST
;Testing Toolox 44
;Cutting parameter
;v120 f0,2 d0,5-1
;Starting the experiment at D=150 L1=500
DEF REAL L1=139 ;Final diameter: external-cutting depth
DEF REAL L2=500 ;Length of the workpiece
N10 G54 G18 DIAMON
N11 TRANS X0 Z=L2 ;Change the origin of the workpiece
N12 T9D1
N20 G0 X=L1+10 Z10
N21 G0 Z5 ;Moving to the starting point
N22 G0 X=L1+5
N23 G96 F0.2 S120 M4 LIMS=3000
N24 G1 X=L1
N25 G1 Z-50 ;Finishing Z
N26 G1=L4+5
N27 GO X=L4+50
N28 M5
N29 G0 Z50
N40 M2
Channel 2: File name: MQLTEST
;Machining the chamfer before testing
DEF REAL L1=150 ;External diameter
DEF REAL L2=500 ;Length of the workpiece
N101 G54 G18 DIAMON
N102 TRANS X0 Z=L2 ;Change the origin of the workpiece
N103 T22 D1
N104 G0 X=L1+20 Z10
N105 G96 F0.15 S100 M4 LIMS=1000
N110 G0 Z5
N120 G0 X=L1+5
N130 G0 X=L1-4 Z1
N131 G1 X=L1+4 Z-3 ;Linear movement
N140 G0 X200 Z20
KTH Royal Institute of Technology Appendix A. Codes
Marta García Tierno 77 of 88
N150 M5
N152 M2
Scania Case Study
Channel 2: File name: SCANIA2017
;Testing Scania cylinder liners
;Cutting parameter
;v550 f0,3 d0,5
;Definition of geometrical parameters
DEF REAL L1=306; Total length (longer than the cylinder itself)
DEF REAL L2=138; Machining diameter
;Moving to the starting position N100
N101 G54 G18 DIAMON
N102 TRANS X0 Z=L1
N103 T22 D1 ;Selection of tool number
N105 G0 Z-205
N106 G0 X=L2+5
;Start machining N110
N111 G6 F0.3 S550 M4 LIMS=1500
N112 G1 X=L2
N113 G1 Z-30
;Returning to initial position N200
N201 G1 X=L2+5
N202 G0 X=L2+80
N203 G0 Z20
N211 M5
M2
Channel 2: File name: SCANIA2017GROOVES
;Definition of geometrical parameters
DEF REAL L1=306 ;Total length (longer than the cylinder itself)
DEF REAL L2=138 ;Diameter of the cylinder
DEF REAL L3=138 ;Diameter of the groove
;Machining grooves
N101 G54 G18 DIAMON
N102 TRANS X0 Z=L1
N103 T23 D1 ;Selection of tool number
N104 G0 X=L2+20 Z10
N105 G0 Z-22 ;Starting Z
N106 GO X=L2+5
;First groove
N111 G96 F0.2 S300 M4 LIMS=1500
N112 G1 X=L2
KTH Royal Institute of Technology Appendix A. Codes
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N113 G1 X=L3 Z-24
N114 G1 Z-27
N115 G1 X=L2 Z-29
N116 G1 X=L2+7
;Second groove
N121 G0 Z-79
N122 G1 X=L2
N123 G1 X=L3 Z-81
N124 G1 Z-84
N125 G1 X=L2 Z-86
N126 G1 X=L2+7
;Third groove
N131 G0 Z-136
N132 G1 X=L2
N133 G1 X=L3 Z-138
N134 G1 Z-141
N135 G1 X=L2 Z-143
N136 G1 X=L2+7
;Fourth groove
N141 G0 Z-193
N142 G1 X=L2
N143 G1 X=L3 Z-195
N144 G1 Z-198
N145 G1 X=L2 Z-200
N146 G1 X=L2+7
;Returning to initial position
N201 GO X=L2+60
N212 G0 Z20
N213 M5
M2
Channel 2: File name: SCANIA2017FIRSTFACING
;First facing
;Definition of geometrical parameters
DEF REAL L1=306 ;Total length (longer than the cylinder)
DEF REAL L2=139 ;Cutting diameter
N101 G54 G18 DIAMON
N102 TRANS X0 ZZ=L1
N103 T23 D1 ;Selection of tool number
N104 G0 x=l2+20 z10
N105 G0 Z-18 ;Starting Z
;Machining
N111 G96 F0.2 S300 M4 LIMS=1500
N112 G1 X=L2
KTH Royal Institute of Technology Appendix A. Codes
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N113 G1 Z-205
N114 G1 X=L2
;Returning to initial position
N211 GO X=L2+20 Z20
N212 M5
2. Matlab Codes for Temperature Analysis
Extraction of one temperature measurement
clc clear all
%Extracting temperature data data=load('ImageMax10.irp'); a=size(data);
%Parameters x1=5;%Diference in temperature at the beginning of the machining x2=10; seg=8.5; %Number of seconds machining %Temperature vector T(:,1)=data(:,1)+0.001*data(:,2)-273.15;
%Time vector t=zeros(a(1),1); t(1)=0;
for i=2:(a(1)-1) aux=0.001*[data(i+1,4)-data(i,4)]; aux2=data(i+1,3)-data(i,3); t(i)=t(i-1)+aux+aux2; end
%Plotting all temperature values plot(t,T) grid on hold on xlabel('Time (s)') ylabel ('Temperature (ºC)')
%Extracting values for cutting time j=1; while([T(j+1)-T(j)]<x1) j=j+1; end aux3=j;
%Time from the raise of T lim=seg+t(aux3); aux4=lim/(t(2)-t(1));
aux4=round(aux4);
KTH Royal Institute of Technology Appendix A. Codes
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t2=t(aux3:aux4); T2=T(aux3:aux4); mean1=mean(T2);
%Smoothing the curve 1 b=size(T2); if rem(b(1),2)==0 T3=sgolayfilt(T2,2,(b(1)-1)); else T3=sgolayfilt(T2,2,b(1)); end
%Deleting strange values u=1; for p=1:(b(1)-1) if(T2(p)<(T3(p)+5)&&(T2(p)>(T3(p)-5))) T4(u)=T2(p); t4(u)=t2(p); u=u+1; end end
Tm(1:a(1))=mean1;
%Cutting time calculation tcut=t(b(1))-t(1)
xmax=t(a(1)-1); ymin=min(T)-20; ymax=max(T)+20;
%Smoothing T4 c=size(T4); if rem(c(2),2)==0 T5=sgolayfilt(T4,2,(c(2)-1)); else T5=sgolayfilt(T4,2,c(2)); end
%Plotting xlabel('Time (s)') ylabel ('Temperature (ºC)') scatter(t,T,3); grid on hold on plot(t4,T4); hold on plot(t4,T5,'linewidth',3); xlim([0 xmax])
mean2=mean(T4) hold on
KTH Royal Institute of Technology Appendix A. Codes
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Plotting multiple temperature curves %Plotting tool wear clc clear all
data=xlsread('data'); nc=data(:,1); DRY1=data(:,2); DRY2=data(:,3); MQL1=data(:,4); MQL2=data(:,5); MQL3=data(:,6); NF1=data(:,7); NF2=data(:,8); aux=size(nc);
scatter(nc, DRY1,18,[1,0.6,0.2],'filled'); hold on plot(nc,DRY1,'LineWidth',0.5,'Color', [1,0.6,0.2],'LineStyle', '- -'); hold on grid on scatter(nc, DRY2,18,[0,1,1],'filled'); hold on plot(nc,DRY2,'LineWidth',0.5,'Color', [0,1,1],'LineStyle', '- -'); hold on scatter (nc, MQL2,18,[0,1,0],'filled'); hold on plot(nc,MQL2,'LineWidth',0.5,'Color', [0,1,0],'LineStyle', '- -'); hold on scatter (nc, NF1,18,[0,0,1],'filled'); hold on plot(nc,NF1,'LineWidth',0.5,'Color', [0,0,1], 'LineStyle', '- -'); hold on scatter (nc, MQL3,18,[1,1,0],'filled'); hold on plot(nc,MQL3,'LineWidth',0.5,'Color', [1,1,0],'LineStyle', '- -'); hold on
max=zeros(aux(1),1); max(:,1)=300; plot(nc,max,'Color',[1,0,0]); hold on
xlabel('N of test specimen'); ylabel('Tool wear (um)'); legend('DRY1','DRY1','DRY2','DRY2','MQL','MQL','NF','NF'); ylim([0 300]);
KTH Royal Institute of Technology Appendix B. Flank Wear Evolution
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APPENDIX B. FLANK WEAR EVOLUTION
Flank wear images x10: Toolox 44 Cemented carbide inserts
0
1
2
3
4
KTH Royal Institute of Technology Appendix B. Flank Wear Evolution
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7
7
7
7
6
6
6
6
8
8
8
8
9
9
9
9
5
6
6
6
KTH Royal Institute of Technology Appendix B. Flank Wear Evolution
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10
9
9
9
0
0,05
0,1
0,15
0,2
0,25
0,3
0 3 6 9 12 15
Fla
nk
wear
(mm
)
Machining time (min)
Dry
MQL
Air
Figure 66. Flank wear vs. machining time, 0.5 mm Toolox 44.
Figure 67. Flank images, evolution of tool wear.
KTH Royal Institute of Technology Appendix C. Surface Roughness Measurements
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APPENDIX C. SURFACE ROUGHNESS MEASUREMENTS
Scania sample Dry 1
Ra (µm) Rz (µm) Rq (µm)
N of test specimen
Ra (µm)
Rz (µm)
Rq (µm)
3.73 16.67 4.42 21 3.73 16.67 4.42
42 3.37 16.77 4.68
63 3.75 21.45 4.52
Average (µm) 3.62 18.30 4.54 Table 26. Surface roughness values JIS 2001, Scania sample, dry machining.
MQL 2 NF 2
N of test specimen
Ra (µm)
Rz (µm)
Rq (µm)
N of test specimen
Ra (µm)
Rz (µm)
Rq (µm)
15 2.2 14.87 2.83 15 2.13 11.57 2.69
30 2.6 12 2.29 30 2.26 13.37 2.82
45 2.27 11.85 2.93 45 2.58 11.78 2.89
60 2.1 10.32 2.57 60 2.39 13.78 2.66
75 2.28 15.41 3.16 75 2.89 12.25 3.26
90 2.48 13.93 3.27 90 2.51 11.18 3.2
105 2.21 12.63 2.66 105 2.69 11.7 3.15
120 2.73 15.74 3.46 120 3 13.4 3.21
135 2.58 14.97 3.4 Average (µm) 2.56 12.38 2.99
150 2.52 15.41 3.4
Average (µm) 2.40 13.71 3.00 Table 27. Surface roughness vaules JIS 2001, MQL with vegetable oil, MQL with NF.
KTH Royal Institute of Technology Appendix D. Poster PVC Annual Conference
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APPENDIX D. POSTER PVC ANNUAL CONFERENCE
The overall goal of PVC, Processvätskecentrum, (Process Fluid Center) is to enhance
competitiveness for Swedish machining with minimal environmental impact. This requires a
competence base that benefits both increased productivity and increased knowledge of process
fluids and its use.
The ambition of PVC is to bring together user and supplier companies in a network within the
framework of the center programs Chalmers MCRs and KTH DMMS operations. Structure for
this network will be based on established work methods within the centers of MCR as the main
coordinator.
The annual conference of PVC took place at KTH-IIP department the 22nd of November 2017.
This project was presented in that conference, in the poster session. The poster utilized for this
presentation is presented in this appendix.
KTH Royal Institute of Technology Appendix D. Poster PVC Annual Conference
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