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MM451 Design for Manufacture and Assembly
Luggage Trolley Design
School of Mechanical and Manufacturing Engineering
DUBLIN CITY UNIVERSITY
Glasnevin, Dublin 9,
Ireland
Tom O’ Carroll Marketing
Aidan Walsh Design
Patrick King Safety
Neville Lawless Manufacturing
Henry Foster Assembly
James McArdle Recycling
DCU University’s Declaration on Plagiarism
Assignment Submission Form
This form must be filled in and completed by the student submitting an
assignment.
Assignments submitted without the completed form will not be accepted.
Names & Student Numbers:
Tom O’Carroll; 10211172
Aidan Walsh; 10211826
Patrick King; 10212063
Neville Lawless; 10212298
Henry Foster; 10210440
James McArdle; 10210918
Programme: CAMM
Module Code: MM451
Assignment Title: Luggage Trolley Design
Submission Date: 04th May 2011
I declare that this material, which I now submit for assessment, is entirely my groups work and has not been taken from the work of others, save and to the extent that such work has been cited and acknowledged within the text of our work. We understand that plagiarism, collusion, and copying is a grave and serious offence in the university and accept the penalties that would be imposed should we engage in plagiarism, collusion, or copying. We have read and understood the Assignment Regulations set out in the module documentation. We have identified and included the source of all facts, ideas, opinions, viewpoints of others in the assignment references. Direct quotations from books, journal articles, internet sources, module text, or any other source whatsoever are acknowledged and the source cited are identified in the assignment references. This assignment, or any part of it, has not been previously submitted by me or any other person of our group for assessment on this or any other course of study.
We have read and understood the referencing guidelines found at http://www.library.dcu.ie/citing&refguide08.pdf and/or recommended in the assignment guidelines.
Name: _________________________ Date: _____________
Page 1
1 Table of contents
1 TABLE OF CONTENTS ..........................................................................................................................................1
2 PRELIMINARY RESEARCH ...........................................................................................................................2
2.1 RECYCLING INCENTIVES ................................................................................................................................... 2 2.2 CHARACTERISTICS OF THE LUGGAGE TROLLEY: ........................................................................................... 3 2.3 MATERIAL SELECTION FOR RECYCLABILITY:................................................................................................. 4 2.4 RECYCLING MANUFACTURING SYSTEM:........................................................................................................ 5 2.5 INITIAL SAFETY GUIDELINES ............................................................................................................................. 6
3 CONCEPTUALIZING THE DESIGN ..........................................................................................................8
3.1 THE BASE.............................................................................................................................................................. 8 3.2 HANDLE .............................................................................................................................................................10 3.3 WHEELS ..............................................................................................................................................................12
4 DESIGN DEVELOPMENT............................................................................................................................ 15
5 SCHEMATIC DIAGRAMS ........................................................................................................................... 17
6 DOCUMENTATION ....................................................................................................................................... 18
6.1 PURCHASE LIST: ................................................................................................................................................18 6.2 BILL OF MATERIALS TO BE MANUFACTURED. ..............................................................................................19 6.3 MANUFACTURING PROCESSES.......................................................................................................................19 6.4 BILL OF MATERIALS FOR ASSEMBLY .............................................................................................................21 6.5 ASSEMBLY PROCESSES ......................................................................................................................................21
7 FINAL DESIGN ................................................................................................................................................. 25
8 REFERENCES ..................................................................................................................................................... 28
9 APPENDIX A ......................................................................................................................................................... 29
10 APPENDIX B ......................................................................................................................................................... 34
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2 Preliminary Research
Before conceptual designs were discussed among the product development team, market
research was conducted to illuminate what was available at the moment and how it was
being marketed. It was decided that the target market for the product would be industrial and private delivery services requiring a means of moving luggage/packages from a
vehicle to its destination without incurring manual handling injury. All research carried
out was secondary or “desk” research. The main source of information on the target
market was the internet. Sites which specialised in trolleys and pallet-trucks were
researched and popular designs were noted as a reference point. Usable transport space is essentially the primary capital earning factor in any delivery
service. Space occupied by a trolley is hence a waste of resources and should be
minimised. A light-weight, foldable trolley would be ideal for moving packages of up to
50kg from a transporter to a point of use without draining usable transport space. This idea forms the focal point of the forecasted marketing strategy.
2.1 Recycling Incentives
Environmental issues are becoming increasingly important to product designers and
manufacturers. Public awareness of the value and how fragile of a whole eco-system of
the plant is constantly increases and the traditional assumption that the cost of ecological burdens is to be shared by the society as a whole is no longer acceptable. In 1993 the
European Union introduced a set of guidelines, the Eco Management and Audit Scheme
(EMAS), which, although still voluntary, has signalled that environmental responsibility
should lie with industry. [1]
This trend is most apparent when considering the environmental impact of worn-out products. The shortage of landfill and waste burning facilities constantly reminds us that
our products do not simply disappear after disposal. It is widely known that the most
ecologically sound way to treat a worn out product is recycling.
Since it is rarely possible or beneficial to recycle a product completely, the aim is to maximize the recycled resources while minimizing the effort that has to be invested. This
balance must be observed while taking economic factors and other social factors into
account. The main objective for the end-of-life value of a product can be realized by two
means [1]:
Improvement of recycling processes by developing more refined recycling technologies (e.g. advanced separating and purifying methods),
Improvement of product design in a recycling-friendly matter.
It is widely believed that only 10-20% of recycling costs and benefits depend on recycling
process optimization. The remainder is already determined at the design stage. Hence it is
an industry wide interest to develop methods and tools for including environmental considerations into product design. [1]
Addressing the environmental problems within the life-cycle of a product requires
rethinking the relationships between manufacturers, suppliers and consumers. By
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developing relationships with suppliers, consumers as well as recyclers in order to
manage materials flow in an environmentally friendly way. To provide the necessary
communication infrastructure and to support collaboration and coordination needs a possible recycling network could be established.[2] It should consist of a “server” which is
the designer and “clients” representing the consumers, recyclers and
materials/components as shown in Figure 1.
Figure 1: Representation of the system life-cycle of a product [2]
In this network the recyclers are considered as dismantlers’/waste management providers. The function of recyclers can be provided by the original product manufacturer, an
independent recycler, or what is widely common today, a contract recycler which recycles
products for a manufacturer who retains ownership of the products. Suppliers have to
honour the requirements of the designer to use recycled materials provided by the
recyclers. [2]
This leads us to the design limitations that have been set for this project:
2.2 Characteristics of the luggage trolley:
Maximum load: 50 kg. Should be foldable (as much as possible). Should be lightweight, for easy carrying.
Handle height should be adjustable for height of person 155-185 cm Expected price range: Euro 25 – 40. Operating temperature: -5 +40 0C. Should be usable outdoors. The expected annual production volume of the device is 10,000 pieces.
Knowing these requirements, the material selection process can begin whilst the
design is being concurrently progressed.
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2.3 Material Selection for recyclability:
Keeping the product life cycle in mind as shown in Figure, suitable materials that could be used for the manufacturing of the trolley where considered. These materials had to be
durable, as the trolley has to withstand daily abuse by the end user. Also the material had
to be suitable for manufacturing and did not require a large capital investment.
Keeping these material qualities in mind but also considering materials that could be
reused / recycled was the main aim of the recycler. The materials that were selected for the main components of the trolley .i.e. the frame, the
handles, and the Wheels were as follows;
2.3.1 The handle:
The Handle was made from a plastic material. The material the most suited for this purpose was ABS (Acrylonitrile butadiene styrene). The
advantage of ABS is that this material combines the strength
and rigidity of the acrylonitrile and styrene polymers with
the toughness of the polybutadiene rubber. [3]
Important mechanical properties of ABS are impact
resistance and toughness. A variety of modifications can be
made to improve impact resistance and toughness. The
impact resistance can be amplified by increasing the proportions of polybutadiene in relation to styrene and also acrylonitrile, although this causes changes in other properties.
The material stability under load is excellent. [3]
ABS is a suitable material, as this material can be recycled with easier once there is no reinforcing fibres additives added to the polymer before/during moulding. Therefore the
ABS material fulfils all the requirements necessary.
2.3.2 The Frame/base:
The Frame and base plate was made from an Aluminium alloy
material. Aluminium is remarkable for the metal's low density and for its ability to resist corrosion due to the phenomenon of
passivation. Structural components made from aluminium and
its alloys are vital to the aerospace industry and are very
important in other areas of transportation and building.
Although aluminium is an extremely common element, the common aluminium minerals are not economic sources of the
metal. Almost all metallic aluminium is produced from the ore
bauxite (AlOx(OH)3-2x). Large deposits of bauxite occur in
Australia, Brazil, but the primary mining areas for the ore are
in Ghana, Indonesia, Russia and Surinam. Smelting of the ore mainly occurs in Australia, Brazil, Canada, Norway, Russia and the United States, because smelting is an energy-
Page 5
intensive process, regions with excess natural gas are also becoming regions for smelting,
Therefore the production of Aluminium is not an environmentally friend process due to
due the destruction of the local ecological system with the regions of mining, also due to the large amounts of energy that is required to produce the material.[4]
However Aluminium has some positive characteristic about it, for one it’s a non-ferrous
metal meaning it will not rust therefore it doesn’t require any form of protective coat such
as painting or powder coasting. This property of the material helps reduce any process with the production of the trolley, because the frame of the trolley does not require any
painting or coating.
Aluminium is also 100% recyclable without any loss of its natural qualities. Recovery of the metal via recycling has become an important
facet of the aluminium industry. Recycling of scrap aluminium
involves melting the scrap, a process that requires only 5% of the
energy used to produce aluminium from ore. In Europe aluminium
experiences high rates of recycling, ranging from 42% of beverage cans, 85% of construction materials and 95% of transport vehicles. [4]
2.3.3 The Wheels:
The wheels would be made from a Synthetic rubber material. This
a monomers, can be mixed in various desirable proportions to be
copolymerized for a wide range of physical, mechanical, and
chemical properties. The monomers can be produced pure and the
addition of impurities or additives can be controlled by design to give optimal properties. The wheels would be a bought in part.
2.4 Recycling Manufacturing system:
A Manufacturing system that has an active recycling process implemented is called a Recycling Manufacturing system. Figure 2show a schematic lay out of the system.
AS shown in Figure 2there are two divisions. (1) Production Division, (2) Disposal
Division.
Figure 2: Recycling with in a manufacturing process. [2]
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1. Production Division is the area were raw materials from suppliers is used to create
components and part resulting in an end product to be sold to a consumer.
2. Disposal Division or recycling is wall waste material and components are collected and sorted in to the various types e.g. plastic or metals. Within the area the material or
components are either checked and reused and sent back into the Production Division or
set of for recycling.
From the Disposal Division the following steps can be taken as the production of the
trolley which involves the purchasing of raw material e.g. the Aluminium, the ABS plastic graduals, and the purchasing of components such as the wheels, fixtures (screws, rivets,
etc.).
Reuse part: - parts can be reused within the plant.
Not-reusable but recycled:- the part can be used but can recycled .i.e. resent back to the supplier or recycling firm to be recycled.
Not-recyclable: - the parts can only be sent to landfill this area should be avoided if
possible.
2.5 Initial safety guidelines
Producers have an obligation to avoid placing dangerous products on the market. The EC General Product Safety Regulations (2004) specifies that “A producer shall not place or
attempt to place on the market a product unless it is a safe product”. Contravention of this
regulation is an offence. [3] Directive 2001/95/EC of the European Parliament on general product safety defines a safe product as “any product which, under normal or reasonably
foreseeable conditions of use including duration and, where applicable, putting into service, installation and maintenance requirements, does not present any risk or only the minimum risks
compatible with the product's use, considered to be acceptable and consistent with a high level of
protection for the safety and health of persons”.[4] The directive goes on to list four points
which should be taken into account in particular. These are [4]:
1. The general characteristics of the product.
2. The effect of the product on other products.
3. The presentation of the product including instructions, warning and any other
information relating to the product.
4. The categories of consumers at risk.
With regard to point 1, in the design stage it was necessary to assess the composition of
the luggage trolley designs, the shape and dimensions of the designs, the safety of moving
or folding parts and the ease of use of the designs. Folding or extending parts should be
easy to operate without risk of injury to the user, while at the same time being strong and
secure. Sharp edges should be avoided as much as possible and the product should be lightweight and manoeuvrable.
The luggage trolley is obviously designed for use in conjunction with other products. It
should be capable of holding up to 50kg of luggage, of varying shapes and sizes, securely,
stably, and without risk of failure. Therefore, a suitably sturdy, versatile design is required. The design should not pose a risk to the luggage it transports or the
Page 7
environment it traverses. Inert materials should be used and, again, sharp edges should
be avoided.
Comprehensive instructions for extending, folding and general use of the product should be provided. Clear guidelines and warnings should be placed on the product itself for
folding mechanisms etc. Information regarding the safe use of the product would also be necessary. Article 5 of directive 2001/95/EC states that “producers shall provide consumers
with the relevant information to enable them to assess the risks inherent in a product throughout
the normal or reasonably foreseeable period of its use, where such risks are not immediately obvious without adequate warnings, and to take precautions against those risks.”[2] It should be noted
however that the presence of warnings does not exempt a producer from regulations
regarding safety. [3]
The luggage is primarily targeted at healthy adults, however, it is likely that children, elderly people etc. may come into contact with the product. This increases the risk of
injury or damage being caused by the product. Consideration of this factor should be
taken in the design process.
Producers are liable for defective products produced by them. Defectiveness is
determined by a lack of safety which could reasonably be expected. [5] Directive 85/374/EEC defines a defective product as one that “does not provide the safety which a person
is entitled to expect, taking all circumstances into account, including: (a) the presentation of the
product; (b) the use to which it could reasonably be expected that the product would be put; (c) the
time when the product was put into circulation.” [5] This highlights the importance of
producing a safe product with clear guidelines. It is in the interest of the producer to manufacture a safe product so that no liability for injury or damage is incurred.
Once the initial ideas for the base, the handle and the wheels had been conceptualized,
they were evaluated from a safety point of view. The above mentioned directives and guidelines were taken into account and recommendations were made accordingly.
Appraisals for each concept are given below
Page 8
3 Conceptualizing the design Market research was a key factor in determining the initial conceptual designs. Based on
the target market, a number of different approaches were investigated.
3.1 The Base
Base design 1 as seen in Table 1 represented the flat-bed style of trolley available on
many websites which provide trolleys to delivery services. Figure 12(a) shows an example of this design. This design was seen to be too bulky to realistically transport
around in a delivery vehicle. Though it may be useful for transporting large cargo from a
train or other large vehicle, it would far exceed the carrying requirement of 50kg for this
target market. Base design 2 was clearly the most common type of base found as part of
the market study. This two wheel design is simple and relatively cheap to produce using the fact that it must be tilted to support the load against the handle.
Figure 12(b) shows the style of trolley represented by this concept. The third and fourth
base designs were not as commonly occurring on the sources researched. This base design
would facilitate a trolley similar to that of design 2 but with the option of it being able to
move while standing freely. This design was also deemed to be bulky and hence difficult
to sell in the target market. Figure 12(c) is an example of a three wheeled design similar
to how these two designs would work.
Table 1: Trolley Base Concepts
1
2
3
4
Designer Simplest Simple Complex Most complex
Manufacturing 2nd Easiest Easiest Hardest 3rd Easiest
Assembly Easiest Easy Hardest Hard
Safety Safest Safe Unsafe, Unstable Unsafe, unstable
Marketing Easy to sell Easiest to sell Difficult to sell Difficult to sell
Recycling Least Wasteful Wasteful Most Wasteful Very Wasteful
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3.1.1 Manufacture’s comments
1. This concept was settled as the 2nd most favourable with regards to
manufacturability. It contains 4 metal tubes and 4 wheel mountings so it has the
minimum number of parts. All the aluminium tubing is a standard sizing and can be
purchased in bulk at a cheaper cost. The symmetrical nature of the design leads to better automation which is desirable. Each castor however requires four drilling operations so
that requires 16 for the base.
2. This is deemed the best concept by the manufacturing team, it contains 4 tube
sections and one section with 3 bends. The addition of hinges requires the same number of drilling operations as castors but the cost of the aluminium tubing is less than the two
castors it replaces. It is felt that the drilling operations are easier catered for the hinges as
there is better access. A minimum 2 sheet thickness is adhered to between holes.
3. Deemed a bad design. Requires 4 tube sections and a 5 th with 3 bends and 2
castors. As with other designs, all standard tubing and wheels can be purchased in bulk. No additional manufacturing positives when compared to concepts 1 and 2. Addition of
two extra wheels requires extra drilling processes and an increased manual handling.
There is an increased chance of errors being made in the manufacturing process.
4. Bad design, Chosen over 3 if a choice has to be made. Exact same design as
concept C less one wheel. 4 less drilling operations are need, but no other discernible differences are present.
3.1.2 Assembly comments
1. This design was deemed the most favourable to assemble. The design is
completely symmetrical requires no individual parts, i.e., all the parts are used
somewhere else in the design. Very few fasteners are required and all the fasteners would
be identical. 2. This was decided to be the 2nd most preferable design. There is symmetry and
many common parts. There are more parts than the previous design due to the hinge
mechanism at the front, though fewer wheels are required.
3. This design was deemed to be the least favourable with regard to assembly. The
design is symmetrical and has some common parts, but has the most parts out of all of the designs. The wheels also differ between the front and rear of the base.
4. This design is quite similar to the previous design, with the exception that at the
front of the trolley there is only one wheel for steering. Due to having fewer parts than
that design, it would be preferable to the previous design.
3.1.3 Safety concerns
1. This concept consists of a flat square base with four wheels, is a solid design which provides excellent stability. One drawback of this idea is the sharp corners at the
front of the trolley. These could potentially injure the lower leg or ankle and could easily
damage property, for example doorframes, if the trolley was not controlled properly.
2. A two-wheel concept is also a stable design which provides good manoeuvrability. However, sharp corners are present in this design also. There is a ledge along the front of
the base which is designed to allow the trolley to stand upright. This edge could pose a
Page 10
serious risk. If somebody happened to get, for example, a foot caught underneath it when
the trolley was loaded, a large force would be exerted on a relatively small area and this
could cause injury. It was suggested that this ledge could be hinged to reduce the required storage space of the trolley when folded. This would add another risk as users
could potentially catch a finger when folding it. The fact that the trolley has to be tipped
means that some of the load must be taken by the user. There is a certain amount of risk
associated with this and there is also an increased risk of the trolley falling backwards
during use. 3. Concept 3 reduces the risk posed by sharp corners but the downside is that
stability is reduced. If loaded carelessly or left on uneven terrain, the trolley could easily
fall to one side. If small wheels are used at the front of the base the trolley may become
difficult to push safely over rough ground. A hinged joint in the middle was suggested but this would result in a weak point which would be susceptible to failure. A hinged
joint in this position would also increase the risk of injury to fingers when the product is
being folded.
4. This is a modified version of the previous concept. While it may be slightly
cheaper to produce, this concept is completely unacceptable from a safety standpoint. It would be very unstable and difficult to use safely.
3.2 Handle
The conceptual designs for the handle seen in Table 2 were broken down to three different
approaches based on the trolleys researched. Handle design 1 was the most commonly
occurring. This design could be made to either fold or telescope in order to be compacted (Fig. 15 (b)), this design would suit the target demographic but would resemble many of
the products currently available and may be difficult to market as an original design.
Design 2 was less common and any similar designs observed were lacking the support
bars on the sides (Fig. 15 (a)), this design was conceived in an attempt to minimise material used and related processing expense. It also allows for a very compact folded
state and with support straps or elastic canopy between support bars it could provide
very even support without great expense which would also suit the delivery services
industry while also maintaining a degree of originality. Design 3 was also unique in that it
was not found during the market research at all. This design is hence purely conceptual. The idea behind it is to create an even bed of support for the load while reducing cost as it
could be injection moulded from a plastic rather than built with a metal frame. It may
however be too stiff and could risk failing without the elasticity of a metal to support a
large load.
3.2.1 Manufacturing comments
1. This is the best solution from a manufacturer’s point of view. It contains 3 sections
with 3 hinge joints. Total 8 parts. It has symmetry about the middle horizontal brace which leads to reduction of original parts. The standard tubing (hollow or solid) can be
easily sourced for mass purchase. The standard hinges can also be purchased. Aluminium
tubing can be used for all sections of the design. There is a lot of manual handling
required however as the factory doesn’t have robot automation.
Page 11
2. This design is the next favourable. It is comprised of 3 sections with attachment of
horizontal supports required. 6 parts in total. As with the other designs standard tubing,
can be easily out sourced for mass purchase. The plastic components are not standard components however, if the plastic components can be injection moulded in house there is
a need only to design and purchase one die for all components as an injection moulding
machine is an available resource. The locking mechanism can be designed for multiple-
uses on the 3 sections as it holds the horizontal supports. Tighter tolerances are needed for
tubing as a high level of stiffness is required when arms are fully extended.
Table 2: Trolley Handle Concepts
3. This is not to be favoured over the other components. It requires 2 sections,
formed with bent sheeting, with internal reinforcement. Although standard tubing and sheet metal should be used a large volume of material is required, needlessly. Complex
bending operations are also needed and there is no possibility of multi-use or
multifunctional components.
3.2.2 Assembly comments
1. The first concept was judged to be the easiest to assemble. It only requires
connection between the parts to be assembled.
1 2 3
Designer Simplest Ok Complex
Manufacturing Easiest 2nd Easiest Hardest
Assembly Easiest Hardest Ok
Safety Hazardous Safe Safest
Marketing Hardest to sell Easiest to sell Ok to sell
Recycling Least Wasteful Wasteful Very Wasteful
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2. The 2nd concept is the most difficult to assemble. There are a number of
mechanisms that will be required in the handle to enable the telescopic folding of the
handle which may be difficult to assemble. 3. The 3rd concept would be easy to assemble. It involves snap-fitting a number of
plastic moulded parts together and attaching a handle to the top of the assembly.
3.2.3 Safety concerns
1. A tubular frame concept, is a simple design, however, it contains a number of
rotating joints which need to lock into place presumably by some kind of snapping
mechanism. This type of joint poses a risk to the user during folding and unfolding operations. Due to the nature of the product it would be folded and unfolded regularly so
this type of design is undesirable from a safety point of view. There is also a danger of
luggage falling through the back of the trolley as it has quite an open structure.
2. A telescopic concept, removes the risk associated with rotating joints. There is still
a danger of catching a finger in the extending tubes. It is thought, however, that this poses less of a risk especially as the extending mechanism would be operated from the handle at
the top which is a safe distance from the dangerous areas. The protruding bars may be a
safety hazard also. They have the potential to cause injury particularly if the trolley fell
over. Again, there is a danger of luggage falling through the bars.
3. This concept is also an extendable design and was deemed to be the safest. There are no rotating joints or protruding parts and the edges are rounded. Luggage cannot fall
through the back of the trolley either. One danger is that the sliding mechanism could
catch fingers. As in the case of concept 2, this would be operated from the top of the
handle.
3.3 Wheels
Three wheel designs were also considered though as wheels would most likely be
standard parts these designs were based entirely on wheels found during market
research. Wheel design 1 from Table 3 is a pneumatic roller bearing wheel; these wheels
are simple, durable and usable on many different surfaces. They would suit the requirement for versatility that a delivery service would have depending on how wide
their delivery range was, meaning that they would work just as well in a rural
environment as in an urban or industrial one. A trolley using this wheel type is seen in
Figure 15(b). The second wheel type is a castor style design. These wheels are suited to
four-wheel trolleys as they facilitate turning without any tilting axle. Castors are highly standardised and hence could be obtained cheaply in high volumes. They are however
generally not as efficient as multi-terrain wheels and may not be as useful outside. Figure
12(a) shows a standard application of castors in trolleys. The third wheel type is the triple-
wheel stair-climbers. These are highly specialised wheels for applications where a trolley
will need to go up and down steps regularly. These wheels would be useful in the delivery business as it is possible that an elevator won’t be available in older buildings or
that an item may be for use on the upper story of a private home. However, these wheels
are assumed to be more expensive to manufacture and hence would add additional cost
to the finished product which may not be in the target price range. Due to the size of the three wheel assembly, they may also require an extra process or slight redesign of the base
Page 13
to fit to the product being developed. Fig. 15 (c) shows an example of a trolley using these
stair-climbing wheels.
Table 3: Trolley Wheel Concepts
Designer Simple Ok Complex
Manufacturing 2nd Easiest Easiest Hardest
Assembly Easiest Hardest Ok
Safety Safest Ok Ok
Marketing Easy to sell Hardest to sell Easiest to sell
Recycling
3.3.1 Manufactures comments
1. Deemed the best concept as it has the least number of attachment areas. And is the
cheapest to bulk buy.
2. The second choice for the manufacturing team as it requires only one point of
attachment; i.e. 1hole to be drilled etc. 3. This wheel idea although it only has one attachment point it is more expensive
and more complex to fix.
3.3.2 Assembly comments
1. The first type of wheel will require attachment using an axle, bearing and
fasteners. This would be the simplest of the wheel types to assemble.
2. The second type of trolley wheels will come pre-assembled. They will only require attachment to the trolley bases. This will require only fasteners to attach. The trolley base
will need to be held upside-down for attachment. These would be the most difficult to
assemble.
3. The final type will require a bearing and fasteners. They will not require the trolley
to be turned upside-down though. They are moderately difficult to assemble
Page 14
3.3.3 Safety concerns
1. The roller bearing wheel is a standard design which can be implemented
reasonably safely.
2. The swivel caster is a requirement for four-wheel designs and is not applicable to
two-wheel designs. This type of wheel has been incorporated safely into many products.
3. The stair climber design, would allow a trolley to be used safely on steps.
However, there is a danger posed by the three wheels in close proximity. There is a
greater potential to catch fingers in this type of design. Also debris could become trapped
between the wheels causing the trolley to jam suddenly. This type of design is also less safe to manoeuvre on level ground as four wheels in a fixed position are in contact with
ground making the trolley more difficult to turn.
Page 15
4 Design development Once the initial design was decided upon a detailed design was started. The program used to create the model was AutoCAD 2008. The designer created a base model initially,
Figure 3Error! Not a valid bookmark self-reference., and then had a meeting with the
other team members to get their opinions and ideas on this design.
The problems with this design were noted as below;
Base is too low to the ground, needs to be
raised Wheels will not move when base is loaded with
goods, need guards Cross supports on handle should be further out
than upright of handle
Need locking mechanism at the base for handle in upright position
How will wheel and base shaft be held in
position Need a mechanism for connecting the straps for
holding on goods to base
All of these comments were implemented into
the design and the next revision of the drawing
can be seen in Figure 5.
At this stage the locking telescopic locking
mechanism for the
handle was to be button operated from the top of the handle. However the assembly engineer noted that this would be very complicated to assemble, this was rectified by putting in
a cam lock at each of the connections between box
sections, Figure 4. The guards were thought to be hard
to manufacture in one piece due to the double round profile so these were changed to a square profile.
The mechanism at base for locking the handle in the upright position was thought unsafe as it was possible hands would need to be used to unlock
base. This was replaced with just a simple up fold of the base to act as a stopping device. Once the design
Figure 3: Detail Trolley Design Rev 0
Figure 5: Detail Trolley Design Rev 1
Figure 4: Cam Lock system
Page 16
reached revision 2 in Figure 7 it was very close to the final design. There needed to be
some device to hold the handle in the upright position when the user would be loading the trolley. So a simple T bar was introduced that would sit in a simple
grooved connection on the base. It was also noted that the cross support bars needed something to keep them in place, circlips were added either side of the ABS joint connectors.
The final design can be seen in Figure 8 with the
finished folded trolley is seen in Figure 6.
Figure 7: Detail Trolley Design Rev 2
Figure 8: Detail Trolley Final Design
Figure 6: Folded Trolley
Page 17
5 Schematic diagrams
Table 4: Schedule of drawings in Appendix A
Item Drawing Name Drawing Number
1 LUGGAGE TROLLEY DESIGN ASSEMBLED DETAIL DFMATRYL01
2 LUGGAGE TROLLEY DESIGN ISOMETRIC VIEW DFMATRYL02
3 LUGGAGE TROLLEY DESIGN FOLDED DETAIL DFMATRYL03
4 LUGGAGE TROLLEY DESIGN FOLDED ISOMETRIC DFMATRYL04
5 LUGGAGE TROLLEY DESIGN EXPLODED VIEW DFMATRYL05
Drawing Schedule
Page 18
6 Documentation
6.1 Purchase list:
6.1.1 Plastic handle:
Either:
Bulk bought x 10000.
Purchase die and injection mould. …..Selected
6.1.2 Slide mechanism housings:
Must be moulded
No opportunity to purchase these as they are specifically designed and no alternative could be settled upon. Same die used as above
Purchase of cam lock mechanism, x1000
6.1.3 Base plastic housing:
Either:
Purchase out
Purchase die and injection mould ….Selected
6.1.4 Extendable trolley arms:
Purchase out .…Selected
3 sizes for x10000 units of each
All hollow
6.1.5 Base plate:
Purchase aluminium sheeting
Purchase aluminium box sections
6.1.6 Wheels:
Purchase
6.1.7 Wheel axle:
Purchase: Solid aluminium Purchase: Hollow tubing
Page 19
6.2 Bill of materials to be manufactured. Table 5: Bill of Materials
All Plastic
Components
Total
Quantity Cost
Number per
trolley
Cost per
trolley
Injection Moulding
Die x1 2,748.28 x1 0.28
Trolley Arms metres
Per
metre
Size A 3500 0.56 x1 0.196
Size B 3500 0.56 x1 0.196
Size C 3500 0.56 x1 0.196
total 0.588
Base Plate
per
tonne
Flat aluminium
plate x10000
50 per Al rolls
40 rolls = 1 tonne
€6,300
200 rolls needed 5 tonnes €31,500 x1
€3.15
U sections
.16m each 3200 0.36
x2 €0.12
Wheels per unit
20000 2.3 x2 9.2
Axle
per
metre
10000 0.5
0.5
Supports
per
metre
20000 0.48 x2 1.92
Total €15.75
6.3 Manufacturing Processes
Prior to settlement on any production routes, general guidelines were presented to the
design team. Although these are not vital to the successful development of a detailed
design, they are rules which have evolved empirically out of trial and error, so it is in the
interest of the team to adhere to them when given the opportunity. If the opportunity is
not available then the question “Why?” should be asked. This lends itself well to the concurrent engineering process and the cyclical nature of it. By questioning why such
guidelines cannot be followed, can lead to more elegant solutions which could have
perhaps been overlooked.
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The following processes have been selected in accordance to the available resources in the
manufacturing plant and good practices and guidelines will be discussed with each.
6.3.1 Injection moulding One mould
Produces all plastic components As with most assemblies of this nature, the use of injection moulded plastics is nearly
unavoidable at some point. In this instance it has been decided that a family mould
should be used rather than a balanced multi-cavity. This is due to the small number (in
mass production volumes) of plastic components needed to be made. It has been calculated that this route is more economical than purchasing a mould for each plastic
component. Each component is cut free from the family tree manually.
Care should be given in this instance as if done correctly no further processing should be
required. Each item has flashings removed if necessary.
There is a playoff here with how tight the tolerances are set for the die and how much
flash is present in the components.
6.3.2 Cutting All aluminium tubes and axel
Manual loading and unloading to automated cutting jig.
Three different cutting stations to cover the 2 sizes of rods being cut and 1 size square aluminium tubing.
Liberal tolerances can be used in all cases as there is no immediate concern for high
dimensional accuracy.
All these saws are available resources in the factory.
6.3.3 Threading of axle Automated threading with on CNC. A reliable datum has been set on both ends of the axel from the previous cutting
operation. Threading of the ends can be carried out with on the CNC with fast production
rate leaving the CNC free to be used for other operations once the quota of 10,000 has
been met.
6.3.4 Progression tool/Punching Optimized material usage required that strip stock aluminium rolls be purchased. A 3
stage progressive die is needed to; Punch triangular areas out.
Ribs added by bending
Axel attachments bent up
Scrap is reduced by nesting parts as close as possible. Large radii are specified for the punch, as sharp corners wear faster and act as stress
concentrators
All holes punched are a minimum 3 times sheet thickness apart and minimum 2 times
sheet thickness from the base edge.
6.3.5 Box section cutting Manually added to saw for cutting v shape groove to allow bending
Page 21
Manually bent.
No need for a bending presses to be utilised here as it is over kill. Aluminium sheeting
can easily be bent by hand or with a bending tool. Tolerances are not strict for this component. This part serves only as a safety and aesthetic
feature. Once welded in place also acts as stiffening device.
6.3.6 Welding Spot weld bent box sections
Spot weld to base
Complete welding station to follow that finishes the welds GMAW gas metal arc welder (MIG) Welder required here and is an available resource. It
is perfectly suited to the requirements. Lends itself well to automation and can be used
with sheets down to 0.5mm, ideal in this instance. Not suitable for inaccessible areas but
shouldn’t be of concern here.
6.4 Bill of Materials for Assembly Table 6 Bill of Materials for Assembly
Description Price
per unit
Required per
assembly
Total
Required
Total
Cost
Price Per
Assembly
Nylon locking nut,
M10 0.1 2 20000 2000 0.2
Circlip, Ø10mm 0.05 4 40000 2000 0.2
Rubber bushing
Ø10mm 0.33 4 40000 13200 1.32
Square back clip
fastener 0.3 2 20000 6000 0.6
Rivet, Al¸ Ø5mm,
length 6mm 0.08 11 110000 8800 0.88
Flat head rivet, Al¸
Ø5mm, length 3mm 0.03 4 40000 1200 0.12
Rubber end cap,
Ø15mm, 0.07 4 40000 2800 0.28
Total cost of fixings =€36,000
Cost of fixings per unit assembled =€3.60
6.5 Assembly processes
Manual assembly was chosen due to the low number of units to be assembled and the
relatively simple assembly of the trolley. It is estimated that the assembly of each unit will take 410 seconds, or 6.8 minutes. The times were based on the symmetry, thickness and
size of the part, and the ease with which the part could be located and manipulated. The
trolleys are to be assembled in three separate stages. The handle and the base will be
Page 22
assembled separately, and the two sub-assemblies will be joined together. This will allow
for concurrent assembly of the trolley. The order for assembly is as follows:
Table 7 Programme for Assembly
Description Action Time
Required
Description Action Time
Required
Handle
Subassembly
Final Assembly
Insert bottom bar
through bottom box 1 5
Place first
bushing 21 21
Attach bar to box using 2 rivets
2 17.6 Insert axle to first bushing
22 22
Insert middle bar
through middle box 3 5
Place wheel 23 23
Insert cam into slot 4 7
Insert axle
through wheel 24 24
Insert lower assembly
through middle box 5 5
Place second
bushing 25 25
Attach bar to box using clip fastener
6 5.8 Insert axle to second bushing
26 26
Insert top bar through
top box 7 5
Insert axle
through bottom box
27 27
Insert cam into slot 8 7 Place 3rd bushing 28 28
Insert lower assembly
through top box 9 5
Insert axle
through 3rd
bushing
29 29
Attach bar to box using
clip fastener 10 5.8
Place wheel 30 30
Position handle on top bar
11 3 Insert axle through wheel
31 31
Secure handle with
rivet 12 8.8
Place fourth
bushing 32 32
Insert top horizontal
bar 13 4
Insert axle
through fourth
bushing
33 33
Secure bar with circlips 14 11.38
Attach lock nut to
axle 34 34
Insert bottom
horizontal bar 15 4
Thread axle
through holder 35 35
Secure bar with circlips 16 11.38
attach second lock nut
36 36
Page 23
Attach safety caps to bars 17 16
Insert latch 37 37
Time for sub-assembly
126.76
Time for sub-
assembly 76.12
Base sub-assembly
Spot weld wheel covers to base
18 100 Total Time
410.28
Rivet "latch" to base 19 37
Rivet "holders" to base 20 70.4
Time for sub-assembly
207.4
By designing products that can be assembled easily, the time required to assemble each
part can be reduced which will lead to increased productivity and decreased labour costs.
The main ways in which assembly times can be improved are
1. Minimising the number of parts: If there are fewer parts, the product will take less
time to assemble, fewer fasteners will be required to combine parts together and cost of
manufacturing may be reduced also.
Instead of using one two separate rods for the horizontal supports, a single piece of tubing was used. The mechanism housings are made from a single piece of IMP. The flanges on
the edge of the trolley base are formed from bending.
2. Minimise the use of fasteners: In some instances, the cost of fastening a part may
cost 6-10 times the cost of the fastener itself. Fasteners also require extra storage space,
may be difficult to feed and may require extra equipment. If fasteners are required, the use of snap-fits may reduce time required for assembly.
Snap fit fasteners are to be used in securing the shaft to the slide mechanism
housings. Flat-backed fittings are being used due to the low clearance between the inner
and outer shafts. Snap fit "circlips" are also used to secure the horizontal support rods
inside the mechanism housing.
3. Keep internal mechanisms accessible: By keeping any internal workings in the
assembly accessible, any work that must be carried out on the insides of the assembly can
be completed quicker.
The only mechanism as such in the design is the wheel axle. The design allows for access to the axle during assembly even once the wheel covers have been
welded to the base of the trolley
4. Use common parts: By using similar parts throughout the design, the cost of each
part can be reduced.
The two horizontal supports use tubing of the same diameter. Common fasteners were used where possible.
Page 24
5. Design parts so that they can be inserted in as many ways as possible: The
majority of parts can be assembled in more than one way. The handle shafts must be
inserted in a particular direction due to the lip on one end, but apart from this, the orientation does not matter. Only the axle holders, mechanism housings and the wheel
covers must be fitted in one particular way.
6. Avoid very small parts: The majority of the parts avoid this rule. The main
exceptions are the latch and latch holder, and the fixings.
7. Avoid design of parts that may tangle or jam when stored in bulk: With the exception of the circlips, there are no parts that can tangle or jam together
8. Minimise assembly directions: The handle subassembly is assembled from the bottom up, and is then joined at the bottom to the base subassembly
Page 25
7 Final design
After consideration of all the possible aspects investigated during the initial conceptual
design phase, the final design was an amalgamation of the design features researched and original ideas from various members of the product development team. The market
research illuminated that there were many companies manufacturing and supplying
trolleys to a similar target market. This meant that in order to secure a profitable share of
the market, a successful design would need to incorporate both functionality and
originality.
The design seen in Figure 9 is the product of a process-of-elimination regarding all
product development experts. From a marketing perspective, this design should satisfy
the needs of a private or industrial delivery services quite efficiently. There are a number of aspects of the final design which make it attractive to the target market:
1. Base – the base is to be thin, pressed steel. This will minimise material usage while
maintaining stiffness due to it being attached to the wheel-guards. This allows the trolley to be lightweight while also being
capable of supporting the desired weight.
The base is a modified version of concept
2.It now sits closer to the ground which
removes the need for the dangerous
ledge at the front. The base sits roughly
halfway between central shaft and the
ground. This gives a ground clearance of
just over 3cm. This allows the trolley to
be used safely on rough terrain while at
the same time allowing the trolley to
stand safely. The danger posed by sharp
corners has been reduced by tapering
the end of the base. Punching will be
used to create weight-saving holes in the
base. Burrs resulting from this operation
will be removed to ensure that the edges
are smooth. As the wheels encroach
upon the base, guards are built into the
design of the base. This ensures that the
wheels can rotate freely and prevents
damage being caused by the wheels rubbing off luggage. The base has been
designed so that it can comfortably support the maximum load without risk of
failure.
Figure 9: Trolley in operation
Page 26
2. Shaft – the three part design of the handle allows for maximum load-supporting capability while also maximising collapsibility. Aluminium tubes which collapse into
each other will provide an easy to manufacture and assemble means of supporting
the horizontal vector of a load while tilted in the mobile position. There were some
minor safety concerns regarding the extension and collapsing mechanism as
mentioned in Section 3.2.3, however, the risk is thought to be very low and the
type of injury that could be caused is extremely minor. Warning stickers will
be placed on the handle which will include a diagram detailing how to operate
the mechanism safely
3. Handle and support bars – The handle is designed for single handed guiding leaving the second hand free to stabilise the load. This is also aided by the support bars at the
top of each of the other two telescoping sections which can be used for balancing and
further bracing the load; or as a secondary handle for shorter packages. A non-toxic
plastic will be used for the handle which allows it to be gripped securely.
Rubber end caps will be placed on the ends of the support bars on. These will
reduce the threat of damage or injury. There is still a risk of luggage falling
through the gaps between the bars but if the
luggage is strapped on securely this should not
cause too much of a problem. The trolley is
folded about the shaft which holds the handle,
base and wheels in place. This presents a danger
of catching fingers between the base and the
handle, however, the trolley must be foldable in
order to meet the design brief. The risk is
minimised by the fact that the handle only
comes into contact with the base in three small
areas, i.e. the housing around the luggage
supporting bars and the housing around the
bottom of the handle. The parts rotate freely,
that is, they are not spring loaded. This reduces
the risk also. 4. Wheels – The wheels chosen were standard
pneumatic trolley wheels. These do not incur any
manufacturing cost, are easy to assemble and can be
bought cheaply in bulk. They may not have the same stair-climbing capability as the triple wheel
design but they are usable on multiple types of
terrain and have a large enough radius that small
steps shouldn’t present too much of a problem.
An instruction booklet describing how to fold and unfold the product, extend and
contract the handle, and load the trolley safely will be included with the product.
Figure 10 Final Design
Page 27
This booklet will also detail the correct method of transporting luggage on the
trolley. The maximum load will be displayed on the trolley itself.
Figure 11: Trolley in use
In summary, the trolley design proposed should be compact enough to be stored in a
delivery vehicle with ease. It should be sufficient to carry at least twice the recommended manual handling load, hence reducing loading and unloading time by a factor of two.
Ideally, a prototype would be developed and tested in a delivery service scenario in order
to investigate any further design recommendations directly from the target market. This
however is seen to be outside the scope of this project.
Page 28
8 References [1]Hoshino T., Yura K., Hitomi K., (1995), Optimization analysis for recycle-oriented
manufacturing systems, , International Journal of Production Research, Vol. 33(8),
pp.2069-2078.
[2]Kriwet, A., Zussman E. and Seliger G., (1995), Systematic Integration of Design-
for-Recycling into Product Design, International Journal of Production Economics,
Vol. 38(1), pp.15-22.
[3] Matweb, (2010),[Internet], Available from:
<http://www.matweb.com/search/DataSheet.aspx?MatGUID=0177ea648dd340abb8
1c25b4efe613ad&ckck=1>, [Accessed 22/04/2010]
[4] Online Metals, (2010), [Internet], Available from:
<http://www.onlinemetals.com/merchant.cfm?step=2&id=71>, [Accessed
22/04/2010]
[5] Statutory Instruments, S.I No. 199 of 2004,European Communities (General
Product Safety) Regulations 2004, Government Publications, Dublin.
[6]Directive 2001/95/EC of the European Parliament and of the Council of 3 December
2001on general product safety, OfficialJournal of the European Communities.
[7] Council Directive of 25 July 1985 on the approximation of the laws, regulations and
administrative provisions of the Member States concerning liability for defective products
(85/374/EEC)
[8]Made-In-China, (2010), [Internet], Available from:<http://shimaometal.en.made-in-china.com/product/AbhxcIkVnoWC/China-Airport-Luggage-Trolley-GG5-.html> [ Accessed
28/04/2011]
[9]Hydraulic and Pallet Truck Services Ltd,(2010), Pallet Truck Sales, [Internet],
Available from:
<http://www.pallettrucksales.com/index.php?option=com_content&view=article&id=58&I
temid=72>[Accessed 28/04/2011)
[10]Ollies Trolleys, (2010), [Internet], Available from: <http://www.olliestrolleys.com/html/on-line_store.html> [Accessed 28/04/2011]
Page 29
9 Appendix A
Page 30
Page 31
Page 32
Page 33
Page 34
10 Appendix B
Figure 13: Initial base concepts
Figure 12: Trolley base designs considered during initial conceptual design phase[8,9]
Page 35
Figure 14: Initial handle concepts
Figure 16: Initial wheel concepts
Figure 15: Trolley handle designs considered during initial conceptual design phase [8, 10]
Recommended