MM451 Design for Manufacture and Assembly Luggage Trolley Design
Tom O’ Carroll
Marketing
Aidan Aidan Wa lsh
Des ign
Patrick King King
Sa fety
Ne ville ville Lawles Lawles s
Manufacturing
Henry Foste r
Asse mbly
Jame s McArdl McArdlee
Recyc ling ling
School Sc hool of Mechanical and Manufacturing Engineering DUBLIN CITY UNIVERSITY Glasnevin, Dublin 9, Ireland
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’Ca O ’Carroll; rroll; 10211172
Aidan Walsh ; 10211826 Patrick King; 10212063 Neville Lawless; 10212298 10212298 Henry Foster; 10210440 James McArdle; 10210918 Programme: CAMM Module Code: MM451 Assignment Title: Luggage Trolley Design Submission Date:
04 th May 2011
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1 Table of contents 1
TABLE TABLE O F CONTENTS CONTENTS ................................................................................................................................ ..........1
2
PRELIMINA PRELIMINARY RY RESEA RCH RCH ...........................................................................................................................2
2.1 2.2 2.3 2.4 2.5 3
RECYCLING INCENTIVES .............................................................................................. ..................................... 2 HARACTERIS TICS TICS OF THE LUGGAGE LUGGAGE TROLLEY TROLLEY:........................................................................................... 3 CHARACTERIS MATERIAL SELECTION FOR RECYCLABILITY:................................................................................................ . 4 RECYCLING MANUFACTURING SYSTEM:................................................................................................ ........ 5 G UIDEL DEL INES INES................................................................................................ ............................. 6 INITIAL SAFETY GUI
CONCEPTUALIZING CONCEPTUALIZING THE DESIGN ..........................................................................................................8
3.1 3.2 3.3
THE BASE................................................................................................ .............................................................. 8 HANDLE .............................................................................................................................................................10 W HEELS ..............................................................................................................................................................12
4
DESIGN DEVELOPMENT ................................................................................................ ............................ 15
5
SCHEMATIC DIAGRAMS ................................................................................................ ........................... 17
6
DOCUMENTATION ................................................................................................ ....................................... 18
6.1 6.2 6.3 6.4 6.5
PURCHASE LIST: ................................................................................................................................................18 O F MATERIALS MATERIALS TO BE MANUFACTURED MANUFACT URED...............................................................................................19 BILL OF MANUFACTURING PROCESSES.......................................................................................................................19 BILL OF MATERIALS FOR ASSEMBLY.............................................................................................................21 ROCESSES ......................................................................................................................................21 ASSEMBLY P ROCESSES
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 designs were discussed among among the product development team, market research was conducted to illuminate what was available at the moment and how it was being marketed. mark eted. It was was decided decided that the target market for the product would be b e industrial and private delivery services requiring a means of moving luggage/packages from a vehicle to its destination without incurring incurrin g manual manu al handling inj injury. ury. All research carried out was secondary or “desk” research. The main source of information on the targ et 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 m inimised. 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 forecasted marketing m arketing strategy. 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 European Union introduced a set of guideli guidelines, nes, the Eco M anagement anagement and Audit Audit Schem S chemee (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 possible recycling network 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. 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 what is widely widely common com mon today, today, a contract recycler which recy cles 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
Characteris Characte ristics tics of the lugg luggage trolley:
Maximum load: 50 kg.
S hould be b e foldable (as much as possible). possible).
Should be lightweight, lightweight, for easy carrying.
Handle height should should be adjustable for height of perso person n 155 155-185 -185 cm
Expected price range: Euro 25 – 40.
Operating temperature: -5 +40 0 C.
Should be usable outdoors. The expected expected annual annua l production production volume volume of the device device is 10, 10,000 000 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 materials that th at were selected selected for the mai m ain n components com ponents of the trolley trolley .i.e. the frame, the t he handles, and the t he 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 (Acr (Acrylonitrile ylonitrile butadiene butadiene styrene). sty rene). 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 additives added added to the polymer before/during b efore/during mouldi mou lding. ng. Therefore the ABS material fulfils all the requirements necessary.
2.3.2 T he Frame/base: Frame/base: The Frame and base plate was made from an Aluminium alloy material. material. Aluminium is remarkable remarkab le for the th e metal m etal's 's low density density and for its ability to resis resistt corrosi c orrosion on due to the phenomenon phenom enon 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 Almost all m etallic etallic aluminium 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, Ghana, Indonesia, Russia Russia and Surinam. S urinam. Smelting S melting of the ore mainly occurs in Australia, Australia, Brazil, Canada, Norway, Russia and the United States, because smelting is an energy-
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intensive process, regions with excess natural gas are also becoming regions for smelting, Therefore the production of Aluminium is not an environm environmental entally ly friend process process due to due the destruction of the local ecological system with the regions of mining, also due to the large amounts amounts of energy that is required to produce the materi m aterial al.. [4] However However Alumin Alum inium ium has some positive characteristic about it, for one it’s a non -ferrous m etal m eaning it will not rust therefore ther efore it doesn’t require requ ire any any form of protective protec tive coat such as painting or powder coasting. This property of the material helps reduce any process with the production of the trolley, trolley, because b ecause the frame of the trolley does not require any painting or coating. Aluminium is also also 100 1 00% % recyclabl recyc lablee without without any loss of its its natural natu ral 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 used to produce aluminium aluminium from ore. In Europe aluminium aluminium experiences high rates of recycling, ranging from 42% of beverage cans, 85% of construction materials materials and 95% of transport vehicles. vehicles. [4] [4 ]
2.3.3 T he Wheels: Wheels: The wheels wheels would be b e made from a Synthetic S ynthetic rubber material. material. This a m onomers, can b e mixed in various various desirable desirable proportions proportions to be copolymerized for a wide range of physical, mechanical, and chemical chem ical properties properties.. The m onomers can be b e produced 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. system . Figure 2 show a schematic lay out of the system. AS shown in Figure 2 there 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 resulting in an end product to b e sold to a consumer. 2. Disposal Division or recycling rec ycling is wall wall waste m aterial and com ponents are collected collected and sorted in to the various types e.g. plastic or metals. Within the th e area the material or components are either checked and reused reused and sent back into the t he Production Divi D ivision sion 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. rec ycled. 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 ”.[4]] The directive goes on to list four points which should be taken into account in particular. These are [4]: 1. The general characteristi characteristics cs of the th e product. 2. The effect of the product on other products. 3. The presentation of the product including instructions, warning and any other information relating relating to the product. 4. The categories 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
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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 norma norm a l or reasonably foreseeable foreseeable period of its use, use, where wh ere such risks risks a re not immed iately obviou ob viouss 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 lack of safety which could reasona reasonably bly be expected. [5] Directive 85/374/EEC defines a defective product as one that “ does not provide the th e safety which a pers p erson on is entitled to expect, taking all circumstances into account, including: (a) the presentation of the product; prod uct; (b) the use use to which it could reasonably reasonably be expected expected that the product product would be b e put; p ut; (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
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3 Conceptualizing the design Market research was a key factor in determining the initial conceptual designs. Based on the target market, m arket, a numb n umb er of different approaches were investiga investigated. ted.
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 large vehicle, vehicle, it would far far exceed the carrying requirement of 50k 5 0kg g 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) 12(b) shows shows the style style of trolley trolley represented by this concept. The third and 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 sell in the target target market. m arket. Figure 12( 12(c) c) is an example of a three wheeled design similar to how these two designs would work. Table 1: Trolley Base Co ncep ncepts ts
2
1
3
4
Designer
Simple Sim plest st
S imple
Complex
Most complex
Manufacturing
2 nd Easiest Easiest
Easiest
Hardest
3 rd Easiest
Assembly
Easiest
Easy
Hardest
Hard
Safety
S afest afest
S afe
Unsafe, Unstable Unsafe, unstable
Marketing
Easy to sell
Easiest to sell
Difficult Diffic ult to sell
Difficult Diffic ult to sell
Recycling
Least Wasteful
Wasteful
Most Wasteful
Very Wasteful
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3.1.1 Manufacture’ Manufacture ’s comments 1. This concept was settled as the 2 nd 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 symm etrical nature nature of the design leads leads to better automation which is desirable. desirable. Each castor however requires four drilling 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 with 3 bends. The addition of hinges requires requires the same number num ber 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 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. identical. 2. This was decided to be the 2 nd most preferable design. There is symmetry and many common parts. There are more parts than the previous design due to the hinge mechanis mech anism m at the front, though fewer wheels are are required. 3. This design was deemed to be the least favourable with regard to assembly. The design design is symmetrical symm etrical and has some comm on parts, parts, but b ut 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 This concept consists of a flat square base with four wheels, is a solid design 1. 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 9
serious serious risk. If somebody som ebody 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 p otentially catch a finger when folding folding it. The fact that th at the trolley trolley has to be tipped means that some of the load must be b e taken by b y the user. There is a certain 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 design could be made to either fold or telescope telescope in order to be b e compacted com pacted (Fig. 15 1 5 (b )), this th is design design would would suit the target target demographic but would would resemble resemb le 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 m aintaining a degree of originality. Design 3 was also unique uniq ue 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.
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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, however, if the th e plastic plastic components c omponents can c an be injection moulded in house there is 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 multipleuses on the 3 sections as it holds the th e 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
1
2
3
Designer
Simple Sim plest st
Ok
Complex
Manufacturing
Easiest
2 nd Easiest
Hardest
Assembly
Easiest
Hardest
Ok
Safety
Hazardous Haz ardous
S afe
S afest
Marketing
Hardest to sell
Easiest Easiest to sell
Ok to sell
Recycling
Least Wasteful
Wasteful
Very Wasteful
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.
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2. The 2 nd 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 which may be b e difficult to assemb assemble. le. rd 3. The 3 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 c atching a finger finger in the th e extending tubes. It is thought, th ought, however, 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 triplewheel 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
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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
S imple
Ok
Complex
Manufacturing
2 nd Easiest
Easiest
Hardest
Assembly Assemb ly
Easiest
Hardest
Ok
Safety
Safest
Ok
Ok
Marketing Mark eting
Easy to sell
Hardest to sell
Easiest Easiest to sell
Recycling
3.3.1 Manufactures comments 1. Deemed the best b est concept as it it has the least least number num ber of attachment areas 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 req uire a bearing and fasteners. fasteners. They will will not require requ ire the trolley to be turned upside-down upside-down though. th ough. They are modera m oderately tely difficult difficult to assemble
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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.
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4 Design Design develop developmen mentt 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 mech anism for connecting connec ting the straps for 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 Figure 3: Detail Trolley Design Rev 0 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 Figure 5: Detail Trolley Design Rev 1 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 design Figure 4: Cam Lock system
Page 15
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 grooved connection on the base. It was wa s 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 6: Folded Trolley
Figure 8: Detail Trolley Final Design
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5 Schematic diagrams Table 4: Schedule of drawings in Appendix A
Drawing Drawing Schedule Schedul e Ite m Drawi ng Name
Drawi ng Numbe r
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
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6 Documentation 6.1
Purchase list:
6.1.1 Plastic handle: Either:
Bulk Bulk b ought ought x 10000. 10 000. 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 of cam lock mechanism, m echanism, x1000
6.1.3 Base plastic housing: Either:
Purchase out Purchase die and injection mould
….Selected
6.1.4 Extendable trolley arms:
Purchase out 3 sizes sizes for x10000 x100 00 units of each each All hollow
.…Selected
6.1.5 Base plate:
Purchase aluminium aluminium sheeting Purchase aluminium aluminium box sections
6.1.6 Wheels:
Purchase
6.1.7 Wheel axle:
Purchase: Soli S olid d aluminium Purchase: Hollow tubing
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6.2
Bill Bill of material m aterialss to be m anufactured.
Table 5: Bill of Materials
All Plastic Components Injection Moulding Die
Trolley Trolley Arms Size A Size B Size C
Total Quantity
Cost
Number per trolley
Cost per trolley
x1
2,748.28
x1
0.28
metres 3500 3500 3500
Per metre 0.56 0.56 0.56
x1 x1 x1 total
0.196 0.196 0.196 0.588
per tonne
Base Plate Flat aluminium plate 50 per Al rolls 40 rolls = 1 tonne 200 rolls needed needed
x10000
5 tonnes
€6,300 €31,500
x1 €3.15
U sections .16m each
3200
Whee Wh eels ls 20000
per unit 2.3
10000
per metre 0.5
20000
per metre 0.48
Axle
Supports
6.3
0.36 x2
€0.12
x2
9.2
0.5
x2
1.92
Total
€15.75
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 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. necessary.. 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 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 threading with on CNC. A reliable datum has been set on both ends of the axel from the previous cutting operation. operation. Threading Threading of the ends can be carri c arried ed 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 B ox section cutting cutting
Manually added to saw for cutting v shape groove to allow bending
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Manually bent. No need for a bending presses to be utilised here as it is over kill. Aluminium sheeting can easily easily be bent b ent by b y 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 0.5m 0 .5mm, m, ideal ideal in this instance. instance. Not suitable for inaccessible inaccessible areas areas but shouldn’t be of concern here.
6.4
Bill of Materials for for Assembly Assem bly
Table 6 Bill of Materials fo r Assembly
Description
Price per unit
Required per assembly
Total Required
Nylon locking nut, M10
0.1
2
20000
2000
0.2
Circlip, Ø10mm
0.05
4
40000
2000
0.2
0.33
4
40000
13200
1.32
0.3
2
20000
6000
0.6
0.08
11
110000
8800
0.88
0.03
4
40000
1200
0.12
0.07
4
40000
2800
0.28
Rubber bushing Ø10mm Square back clip fastener Rivet, Al ¸ Ø5mm, length 6mm Flat head rivet, Al ¸ Ø5mm, length 3mm Rubber end cap, Ø15mm,
6.5
Total Cost
Price Per Assembly
Total cost of fixings fixing s
= €36,000
Cost of fixings fixing s per unit assembled
= €3.60
Assem Assembly bly proce processes sses
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
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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 Des cription
Action Action
Time Required
Insert lower assembly through middle box Attach Attach bar b ar to box using clip fastener Insert top bar through top box Insert cam into slot slot Insert lower assembly through top box Attach Attach bar b ar to box using clip fastener Position handle on top bar S ecure handle with rivet Insert top horizontal bar S ecure bar with circlips Insert bottom horizontal bar S ecure bar with circlips circlips
Action
Time Required
21
21
22
22
23
23
24
24
25
25
26
26
27
27
28
28
29
29
30
30
31
31
32
32
33
33
34
34
35
35
36
36
Final Fin al Asse As sembly mbly
Handle Subassembly Insert bottom bar through through botto b ottom m box Attach Attach bar b ar to box using 2 rivets Insert middle bar through middle box Insert cam into slot
Description
1
5
2
17.6
3
5
4
7
5
5
6
5.8
7
5
8
7
9
5
10
5.8
11 12
14 15 16
Place first bushing Insert axle to first bushing Place wheel Insert axle through wheel Place second bushing Insert axle to second bushing Insert axle through bottom box Place 3rd bushing Insert axle through 3rd bushing Place wheel
Insert axle through wheel Place fourth 8.8 bushing Insert axle 13 through 4fourth bushing Attach Attach lock nut n ut to 11.38 axle Thread axle 4 through holde h olderr attach attach second 11.38 lock lock nut 3
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Attach safety caps to bars
17
Time for for sub-assemb su b-assemblly
16 126.76 126 .76
Insert latch Time for subsu bassembly
37
37 76.12
Base su b-assembly b-assembly Spot weld wheel covers to base Rivet Rivet "latch" to base b ase Rivet "holders" to base Time for for su s u b-assemb b-as sembly ly
18
100
19 20
37 70.4 207.4
Total Time
410.28
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 m ain wa ways ys in which assemb assemb ly times can be b e improved are 1. Minimising the number numb er of parts: parts: If there are fewer parts, the th e product wil willl take less time to assemble, fewer fasteners will be required to combine parts together and cost of manufacturing may m ay 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 req uired for assemb assembly. ly. S nap fit fasteners are are to be b e used in securing the shaft to the slide slide mechanis mec hanism m 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 inside the m echanism housing. 3. Keep internal mechanisms accessible: By keeping any internal workings in the assemb assembly ly accessible, accessible, any work work that must mu st be carried carried out on the insides ins ides of the assemb assembly ly 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 similar parts throughout the design, the cost c ost of each part can be reduced. The two horizontal supports use tubing of the same diameter. Common fasteners were used where possible.
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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 c irclips,, there th ere 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
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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 design which make m ake it attractive to the target market: 1.
Base – the base b ase is is to be thin, pressed pr essed steel. This will will minimise minim ise 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 Figure 9: Trolley in operation 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.
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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 telescoping sections sections which can b e 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 are easy 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 Figure 10 Final Design
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. Page 26
This booklet will also detail the correct method of transporting luggage on the trolley. The maximum load will will be b e displayed displayed on the trolley trolley itself. it self.
Figure 11: Trolley in use
In summary, summ ary, the trolley trolley design design proposed should be com pact enough to be b e 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 27
8 References [1]Hoshino T., Yura K., Hitomi Hitomi K., (1995), (1995 ), Optimizati Optim ization on analysis analysis for recycle-oriented recycle-oriented Production Research, Research, Vol. Vol. 33(8), 33(8) , manufacturing manufacturi ng systems, systems, , International Journal of Production pp.2069-2078. [2]Kriwet, [2]Kriwet, A., Zussman E. and Seliger G., (1995), (199 5), Systemati c Integration of DesignDesignProduction Economics, for-Recycli for-Recycling ng int o Product Product Design , International Journal of Production Vol. 38(1), pp.15-22. [3] Matweb, (2010),[Internet], Available vailable from: , [Accessed 22/04/2010] [4] Online Metals, (2010), [Internet], [Internet], Available vailable from: , [Accessed 22/04/2010] [5] Statutory Sta tutory Instrume Instruments, nts, S .I No. 199 of 2004 2004,, European European Communit Comm unities ies (General (General Government Publications, Dublin. Product Product Safety) Regulations Regulati ons 2004 , Government [6]Directi Directive ve 2001/95/EC of the t he European European Parliament Parli ament and of of the Council C ouncil of 3 December December OfficialJournal of the European European Communities. 2001on general general product safety safet y , OfficialJournal [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 [8]M ade-In-China, -In-China, (2010 (20 10), ), [Internet], [Internet], Availa Available ble from: f rom:<< http://shimaometal.en.made-inchina.com/product/AbhxcIkVnoWC/China-Airport-Luggage-Trolley-GG5-.ht ml> [ Accessed 28/04/2011]
[9]Hydraulic and Pallet Truck Truck Serv S ervices ices Ltd,(2010), Ltd,(201 0), Pallet Truck Truck Sa S a les, les, [Internet], [Internet], Available from: [Accessed 28/04/2011) [10]Ollies [10]Ollie s Troll Trolleys, eys, (2010), (2010), [Internet], [Internet], Available Availabl e from: from: [Access [Accessed ed 28/04/201 28/0 4/2011] 1]
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9 Appendix A
Page 29
Page 30
Page 31
Page 32
Page 33
10 Appendix B
Figure 12: Trolley base designs considered considered during initial conceptual design phase[8,9]
Figure 13: 13 : Initial base concepts
Page 34
Figure 14: Initial handle handle concepts
Figure 15: Trolley Tr olley handle designs designs considered considered during initial conceptual conceptual design phas phase e [8, 10]
Figure 16: Initial wheel concepts concepts
Page 35
