Design for Manufacture and Assembly Luggage Trolley Design

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

http://moodle.dcu.ie/course/view.php?id=29674

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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.

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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

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

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.

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-

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]

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

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

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

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

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.

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.


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

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.


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

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.


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


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.

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 4: Cam Lock system

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 8: Detail Trolley Final Design

Figure 6: Folded Trolley

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

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

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.

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

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

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

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.

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

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

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

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.

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]

9 Appendix A

10 Appendix B

Figure 13: Initial base concepts

Figure 12: Trolley base designs considered during initial conceptual design phase[8,9]

Figure 14: Initial handle concepts

Figure 16: Initial wheel concepts

Figure 15: Trolley handle designs considered during initial conceptual design phase [8, 10]

Design for Manufacture and Assembly Luggage Trolley Design

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