i

BOOTHYORD DEWHURST AND HITACHI AEM DESIGN FOR ASSEMBLY:

A COMPARATIVE STUDY

MUHAMAD FARKHANIF BIN JAMALUDDIN

Report submitted in fulfillment of the requirements

for the award of the degree of

Bachelor of Mechanical Engineering with Manufacturing Engineering

FACULTY OF MECHANICAL ENGINEERING

UNIVERSITI MALAYSIA PAHANG

DECEMBER 2010

ii

UNIVERSITI MALAYSIA PAHANG

FACULTY OF MECHANICAL ENGINEERING

We certify that the project entitled Boothyord Dewhurst and Hitachi AEM Design for

Assembly: A Comparative Study is written by Muhamad Farkhanif Bin Jamaluddin. We

have examined the final copy of this project and in our opinion; it is fully adequate in

terms of scope and quality for the award of the degree of Bachelor of Engineering. We

herewith recommend that it be accepted in partial fulfilments of the requirements for the

degree of Bachelor of Mechanical Engineering with Manufacturing Engineering.

Dr. Akhtar Razul Razali …………………………….

Examiner Signature

iii

SUPERVISOR’S DECLARATION

“I hereby declare that I have read this project report and in my opinion this project

report is sufficient terms of scope and quality for the award of the degree of Bachelor

of Mechanical Engineering with Manufacturing Engineering.”

Signature :

Name of Supervisor : MR. MAHENDRAN A/L SAMYKANO

Position : LECTURER

Date : 06 DECEMBER 2010

iv

STUDENT’S DECLARATION

I Muhamad Farkhanif Bin Jamaluddin declare that this report entitled “Boothyord

Dewhurst and Hitachi AEM Design for Assembly: A Comparative Study “is the result

of my own research except as cited in the references. The report has not been accepted

for any degree and is not concurrently submitted in candidature of any other degree.

Signature :

Name : MUHAMAD FARKHANIF BIN JAMALUDDIN

ID Number : ME08012

Date : 06 DECEMBER 2010

vi

ACKNOWLEDGEMENTS

First of all, I have to readily acknowledge and thank to Allah, The Omnipotent

and Omniscient who created everything and in giving me the ability to start and

complete this project. This project was conducted under the supervision of Mr.

Mahendran A/L Samykano in University Malaysia Pahang (UMP). I am very grateful to

him for his patience and his constructive comments that enriched this research project.

His time and efforts have been a great contribution during the preparation of this thesis

that cannot be forgotten forever.

I would also like to thank Mr. Hadi bin Abdul Salaam as my academic advisor.

This study would not be complete without the support from him. Thank you for all the

help and advice given. I also gratefully acknowledge the assistance of everybody who

helped in the execution of this project in UMP. I also thank to all Mechanical students

for their friendship and help when thinking through problems and for sharing their

knowledge of DFMA. Finally, I would like to thanks to my family for their continuous

support and confidence in my efforts.

vii

ABSTRACT

Children's tricycles are typically used by children between the ages of two until four

before they usually switch to a bicycle. This product is a good design to be

commercialized. However, before releasing to the market, the product has to be cheap

and good quality. Therefore, to achieve this goal, design for manufacture and assembly

methodologies are used to evaluate the design of the product. Specifically, DFMA,

which is Boothroyd-Dewhurst and Hitachi AEM, are used to evaluate the product. The

strategy of evaluating the existing design is first to choose the available product in the

market in order to solve a problem. The products choose were then disassembled into

several families or sub-assemblies. This is for understanding how the parts functioning

during normal operating mode. After that, each parts been critics and study if there is a

chance for redesign. Finally, referring to result from current product based on

Boothroyd-Dewhurst and Hitachi AEM method, the new parts designs are generated.

Than the results for both analyses for improvement design are compared.

viii

ABSTRAK

Basikal roda tiga biasanya digunakan oleh kanak kanak berusia dua hingga empat tahun

sebelum mereka beralih kepada basikal. Produk tersebut adalah sangat berpotensi untuk

dipasarkan. Walau bagaimanapun, produk itu haruslah berkualiti dan murah sebelum

ianya dijual di pasaran. Oleh yang demikian, untuk mencapai matlamat tersebut, kaedah

“Design for Manufacture and Assembly” (DFMA) digunakan untuk menilai reka bentuk

produk. Dua kaedah yang berbeza digunakan untuk menilai reka bentuk produk iaitu

kaedah DFMA yang berdasarkan teknik Boothroyd-Dewhurst dan teknik Hitachi AEM.

Strategi dalam menilai potensi rekabentuk sedia ada bermula dengan pemilihan produk

yang sesuai dan berpotensi untuk dibangunkan. Kemudian, produk yang dipilih akan di

leraikan mengikut kategori yang tertentu bagi memudahkan proses pemahaman cara

produk berfungsi. Selepas itu, setiap komponen akan dikaji dan dikritik mengenai cara

pemasangan dan pengendaliannya untuk memastikan komponen yang boleh diasingkan

atau dicamtum. Akhirnya, merujuk keputusan dari produk semasa berdasarkan teknik

Boothroyd-Dewhurst dan teknik Hitachi AEM, reka bentuk komponen baru dibuat.

Kemudian keputusan kedua dua analisis untuk rekabentuk yang telah diperbaiki

dibandingkan.

ix

TABLE OF CONTENTS

Page

EXAMINER DECLARATION

SUPERVISOR DECLARATION

STUDENT DECLARATION

DEDICATION

ACKNOWLEDGEMENT

ii

iii

iv

v

vi

ABSTRACT vii

ABSTRAK viii

TABLE OF CONTENTS ix

LIST OF FIGURE xii

LIST OF TABLE

LIST OF SYMBOLS

LIST OF ABBREVIATIONS

xiii

xvi

xvii

CHAPTER 1 INTRODUCTION

1.1 Introduction 1

1.2 Problem Background 2

1.3 Problem Statement 2

1.4 Objective of Studies 2

1.5 Scope of Studies 3

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction 4

2.2 Design For Assembly 4

2.3 DFA Guidelines 5

2.4 Various Method of DFA 6

2.4.1 Boothroyd-Dewhurst DFA Method

2.4.2 Hitachi Assemblability Evaluation Method

2.4.3 Lucas Hull DFA Method

6

10

16

x

2.5 Comparing Various Method of DFA 22

2.6 Summary

23

CHAPTER 3 METHODOLOGY

3.1 Introduction

3.2 Design of The Study

24

24

3.3 Process Flow Chart 26

3.4 Framework of the study 27

3.4.1 Gathering the Information of parts/product.

3.4.2 Current Design Review

27

27

CHAPTER 4 RESULT AND DISCUSSION

4.1 Introduction

4.2 Product Description

4.3 Specification of Children Tricycle

4.4 Part Critique

4.5 Figures and Dimension of The Part

4.6 Product Tree For Current Design

4.7 Product Assembly Operation For Current Design

4.8 Application of Hitachi AEM on Current Product

4.9 Application of Boothroyd Dewhurst on Current Product

4.10 Suggestion of Improvement on Current Tricycle

4.11 Product Tree for Improvement Design

4.12 Product Assembly Operation For Improvement Design

4.13 Application of Hitachi AEM on Improvement Product

4.14 Application of Boothroyd Dewhurst on Improvement

4.15 Comparison Curent Design And Improvement Design

4.16 Comparison Hitachi AEM and Boothroyd Dewhurst

4.17 Summary

31

31

32

33

35

54

55

60

69

80

82

83

88

97

108

111

114

xi

CHAPTER 5 CONCLUSION & RECOMENDATION

5.1 Introduction

5.2 Conclution

5.3 Future Recommendation

115

115

116

REFERENCES 116

APPENDICES

A1 Gantt Chart FYP 1 119

A2 Gantt Chart FYP 1 120

B1 Middle current assembly DFA software 121

B2

B3

B4

C1

C2

C3

C4

D1

D2

D3

Front current assembly DFA software

Rear current assembly DFA software

Front wheel current assembly DFA software

Middle improvement assembly DFA software

Front improvement assembly DFA software

Rear improvement assembly DFA software

Front wheel improvement assembly DFA software

Hitachi AEM penalty scores

Boothyord Dewhurst manual handling

Boothyord Dewhurst manual insertion

122

123

124

125

126

127

128

129

130

128

xii

LIST OF FIGURE

Figure No. Page

Figure 2.1 Boothroyd Dewhurst DFA analysis. 7

Figure 2.2 The operation model of an assembly station 11

Figure 2.3 Basic Element Example 15

Figure 2.4 Lucas hull DFA analysis. 17

Figure 3.1 Flowchart of the project methodology 26

Figure 4.1 Children tricycle current product 33

Figure 4.2 Children Tricycle Product Tree 54

Figure 4.3 Middle Assembly operaton sequence for current design 55

Figure 4.4 Front Assembly operaton sequence for current design 56

Figure 4.5 Front Wheel Assembly operation sequence for current

design

57

Figure 4.6 Rear Assembly operation sequence for current design 58

Figure 4.7 Main Assembly operation sequence for current design 59

Figure 4.8 Children tricycle product tree for improvement design 82

Figure 4.9 Middle Assembly operaton sequence for improvement

design

83

Figure 4.10 Front Assembly operaton sequence for improvement design 84

Figure 4.11 Front Wheel Assembly operation sequence for improvement design 85

Figure 4.12 Rear Assembly operation sequence for improvement design 86

Figure 4.13 Main Assembly operation sequence for improvement design 87

Figure 4.14

Figure 4.15

Figure 4.16

Figure 4.17

Figure 4.18

Comparison basket design

Comparison chassis design

Comparison Seat design,

Comparison front cover design

Comparison rear rim design

108

108

109

110

110

xiii

Figure 4.19

Figure 4.20

Comparison product in 1 hour

Comparison total efficiency

113

113

xiv

LIST OF TABLE

Table No. Page

Table 2.1 DFA worksheet analysis 8

Table 2.2 the relationship between AEM score, assemblability, and

assembly cost

12

Table 2.3 Production information and evaluation information processing. 12

Table 4.1 Children Tricycle Specification. 32

Table 4.2 Part Critique and Material 33

Table 4.3 Chassis (base). 35

Table 4.4 Cap Fork. 35

Table 4.5 Tricycle Dashboard 36

Table 4.6 Front Cover. 36

Table 4.7 Pin. 37

Table 4.8 Pin Clip. 37

Table 4.9 Front Wheel. 38

Table 4.10 Paddle Shaft. 38

Table 4.11

Table 4.12

Table 4.13

Table 4.14

Table 4.15

Table 4.16

Table 4.17

Table 4.18

Table 4.19

Table 4.20

Table 4.21

Table 4.22

Wheel Holder.

Pin Holder.

Hand Grip.

Side Mirror.

Horn

Wheel Clip.

Big Washer.

Medium Washer

Front Rim.

Rear Rim.

Bracket.

Paddle

39

39

40

40

41

41

42

42

43

43

44

44

xv

Table 4.23

Table 4.24

Table 4.25

Table 4.26

Table 4.27

Table 4.28

Table 4.29

Table 4.30

Table 4.31

Table 4.32

Table 4.33

Table 4.34

Table 4.35

Table 4.36

Table 4.37

Table 4.38

Table 4.39

Table 4.40

Table 4.41

Table 4.42

Table 4.43

Table 4.44

Table 4.45

Table 4.46

Table 4.47

Table 4.48

Table 4.49

Table 4.50

Table 4.51

Table 4.52

Table 4.53

Table 4.54

Table 4.55

Seat

Seat Cover.

Bolt Seat

Screw U Tube.

Screw Cover Seat.

Screw Front Cover

Screw Dashboard.

Screw Bracket.

Screw Basket.

Big Nut.

Medium Nut

Bush.

Rear Wheel.

Basket

Lifter

U Tube

Fork Truss.

Current Middle Assembly Hitachi Worksheet A

Current Middle Assembly Hitachi Worksheet B

Current Front Assembly Hitachi Worksheet A

Current Front Assembly Hitachi Worksheet B

Current Rear Assembly Hitachi Worksheet A

Current Rear Assembly Hitachi Worksheet B

Current Front Wheel Assembly Hitachi Worksheet A

Current Front Wheel Assembly Hitachi Worksheet B

Current Main Assembly Hitachi Worksheet

Current Middle Assembly Boothroyd Dewhurst Worksheet

Current Middle Assembly Software DFA

Current Front Assembly Boothroyd Dewhurst Worksheet

Current Front Assembly Software DFA

Current Rear Assembly Boothroyd Dewhurst Worksheet

Current Rear Assembly Software DFA

Current Front Wheel Assembly Boothroyd Dewhurst Worksheet

45

45

46

46

47

47

48

48

49

49

50

50

51

51

52

52

53

60

61

62

63

64

65

66

67

68

70

71

72

73

74

75

76

xvi

Table 4.56

Table 4.57

Table 4.58

Table 4.59

Table 4.60

Table 4.61

Table 4.62

Table 4.63

Table 4.64

Table 4.65

Table 4.66

Table 4.67

Table 4.68

Table 4.69

Table 4.70

Table 4.71

Table 4.72

Table 4.73

Table 4.74

Table 4.75

Table 4.76

Table 4.77

Table 4.78

Table 4.79

Current Front Wheel Assembly Software DFA

Current Main Assembly Boothroyd Dewhurst Worksheet

Current Main Assembly Software DFM

Suggestion Improvement

Improvement Middle Assembly Hitachi Worksheet A

Improvement Middle Assembly Hitachi Worksheet B

Improvement Front Assembly Hitachi Worksheet A

Improvement Front Assembly Hitachi Worksheet B

Improvement Rear Assembly Hitachi Worksheet A

Improvement Rear Assembly Hitachi Worksheet B

Improvement Front Wheel Assembly Hitachi Worksheet A

Improvement Front Wheel Assembly Hitachi Worksheet B

Improvement Main Assembly Hitachi Worksheet

Improvement Middle Assembly Boothroyd Dewhurst Worksheet

Improvement Middle Assembly Software DFA

Improvement Front Assembly Boothroyd Dewhurst Worksheet

Improvement Front Assembly Software DFA

Improvement Rear Assembly Boothroyd Dewhurst Worksheet

Improvement Rear Assembly Software DFA

Improvement Front Wheel Assembly Boothroyd Dewhurst

Worksheet

Improvement Front Wheel Assembly Software DFA

Improvement Main Assembly Boothroyd Dewhurst Worksheet

Improvement Main Assembly Software DFM

Totals comparison between current and improvement design.

77

78

79

80

88

89

90

91

92

93

94

95

96

98

99

100

101

102

103

104

105

106

107

111

xvii

LIST OF SYMBOLS

Ed Functional efficiency

Ema Design efficiency

Nmin Theoretical minimum number of parts

Ta Basic assembly time = 3 second

T h Handling time

Tma Estimated time to complete the assembly of the product

Ti Insertion time

xviii

LIST OF ABBREVIATIONS

AEM Assemblability Evaluation Method

CAD Computer-aided design

CAE Computer-aided engineering

CE Concurrent Engineering

CFE Candidate for Elimination

DFA Design for Assembly

DFM Design for Manufacture

DFMA

NPD

Design for Manufacture and Assembly

New Product Development

CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION

New Product Development (NPD) is a complex and creative process, which is

inherently difficult to manage and improve. Having a great design is one thing, bringing

that design effectively to market is another. The ability to deliver innovative products to

the market on time, at the right cost and quality is a good indicator of a company’s NPD

capability. The significance of NPD in the business value chain must not be

Underestimated, gone are the days where companies can simply compete on quality and

cost.

Developing successful product requires the ability to predict, early in the product

development process, the life cycle impact of design decisions. Any misjudges can leads

to poor product designs that may cause unforeseen problems and excessive costs. Cost

to redesign at this late stage can be prohibitive. Sometimes companies must simply

accept higher manufacturing costs and reduced product effectiveness resulting from

early design errors.

In this chapter, an overview of the background, objectives and scope of this

project are reviewed. Basically, the objective of this study is to redesign a new selected

product for a better design and lower production cost. Here, the DFA Method was

applied to analyze the original product (children tricycle). Lastly, in this chapter, the

overall thesis outlines are reviewed and discussed in general.

2

1.2 PROJECT BACKGROUND

Design for assembly (DFA) is a way to improve assembly ease and reduce

assembly time. It can also reduce product costs by reducing the number of parts,

optimizing manufacturing processes, simplifying parts handling and improving product

assembly. Furthermore, the implementation of DFA can encourages the design of

products to be produced at minimum cost with maximum quality and reliability. Many

leading companies such as Ford, Kodak, General Motors, IBM, NCR, Xerox and more

have save millions of money when using DFA analysis in their designs.

Three of the better-known quantitative evaluation techniques has been used in

industry are Boothroyd-Dewhurst (USA), Lucas (UK) and Hitachi (Japan). However,

this project only focuses on design for assembly using Boothroyd Dewhurst method and

Hitachi Assembleability Evaluation Method (AEM)

1.3 PROBLEM STATEMENTS

Each new product is a good design to be commercialized. However, before

releasing to the market, the product has to be cheap and good quality. Therefore, to

achieve this goal, design for manufacture and assembly methodologies are used to

evaluate the design of the product. Specifically, DFA, which is Boothroyd- Dewhurst

Method and Hitachi method are used to evaluate the product in this project. The results

for both analyses are compared to look for any variation in term of parts to be

eliminated and combined.

1.4 OBJECTIVE OF STUDIES

The aim of this project are to:

1) To design and improve existing design by using DFA method

2) Comparing 2 method DFA and choice the best evaluation method

3

1.5 SCOPE OF STUDIES

In order to achieve the objectives the following scope of studies are performed:

1) Information contents gathering

a. Find out part function for each component.

b. Dimensioning the current design using manual measured.

c. Modeling the CAD drawing of current design by using Solid works

software.

2) Product select

a. original design analysis

b. new design analysis

3) Evaluate the product(children tricycle) based on Hitachi Assembleability

Method and Boothroyd Dewhurst.

4

CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

This chapter provides a review of the concept of product design and methods of

product developments. This chapter also relates how product design affects the cost,

cycle time, and overall product quality. Besides that, this chapter also includes the

information about advantages and disadvantages of DFA method, various methods of

DFA and basic design concept and guidelines.

2.2 DESIGN FOR ASSEMBLY

The manufacturing process of assembly is generally thought of as consisting of

two distinct operation: handling followed by insertion. Both handling and insertion can

be done either manually or automatically (C. Poli, 2004)

In this project, type of assembly that must be considered is manual assembly.

Design for assembly (DFA) may be defined as “ a process for improving product design

for easy and low-cost assembly, focusing on functionality and on assimilability

concurrently .

Design for assembly (DFA) analyzes product designs to improve assembly ease

and reduce assembly time. Often this is accomplished through a reduction in part count.

The implementation of DFA techniques has played an important role in reducing costs

of manufacturing over the last two decades. It is apparent that for both manual and

automated assembly, the effective methods to reduce assembly costs were those applied

during design; manufacturing and production changes have less impact on product cost.

5

The majority of commercial DFA methodologies developed in the last 15 years are

applicable only during the embodiment design phase. The ability to apply DFA analysis

at the conceptual design stage has been neglected. As a result, the DFA methods then

force another iteration on the design, thus consuming time, material, and financial

resources (R. B. Stone 2004)

2.3 DFA GUIDELINES

Different book described DFA Guidelines in different ways. Some authors list

many guidelines and described it with detail while other authors categories it with few

list before divided the main principle to another few principle. But surely the main

objectives for all guidelines remain same, to reduce the cost of assembly. The principles

of DFA are:

1) Reduce the part count. The objective of this guidelines is to minimize the total

number of parts. There is two ways how this objectives can be achieved: first,

design for minimum number of part and second, minimize number of fasteners

and their components. (C. Poli, 2004)

2) Design for minimum number of part. Focussing on the main parts, when number

of part is decreasing, the cost the assembly and whole product can decreasing.

There is 3 factor that should be considered. First, reduce the number of part.

Second, remove non essential component with its function still achieved and

third, combine several part into one components and manufactures as integral

multifunctional component. (C. Poli, 2004)

3) Minimize number of fasteners and their components. Screw and washers can

increase the cost and time to assembly. Other alternatives fasteners can be used

to replace the screw and washers, such as snap fits press fits and molded hinges,

straps or hook. It seems obvious with this technique (reduce part count), the

assembly costs would be less. Butt the question remains whether the overall

manufacturing costs have been reduced. (Knut Holt 2002)

4) Standardize on component, materials and fasteners. Generally, small similar

shaped component can be difficult to differentiate. Feeders can become jammed

because wrong part have been fed in by operators. This also can save the

storage, inventory and ordering cost and time. (C. Poli, 2004)

6

2.4 VARIOUS METHOD OF DFA

There are various methods that were using in Design for Assembly in industry

nowadays such as:

1) The DFA method exploited by Boothroyd Dewhurst Inc, USA.

2) The Hitachi Assemblability Evaluation Method (AEM) by Hitachi Ltd,

Japan.

3) The Lucas Design for Assembly Methodology by Lucas-Hull, UK.

2.4.1 Boothroyd-Dewhurst DFA Method

Design for assembly (DFA) that formulated by Boothroyd and Dewhurst are

one of the most widely DFA methodologies which is used on productivity

improvement through product design in term of assembly ease and reduce assembly

time. Boothroyd and Dewhurst DFA methodology has been recognized as a very

useful tool in increasing compet it iveness by reducing the part number of

components, simplifying the product design structure and improving product design

reliability. The procedure for analyzing product for manual assembly Boothroyd and

Dewhurst method is summarized as following below (Stoll W.H, 1999).

1) Obtain the best information about the product or assembly. Useful

items include engineering drawing, exploded three-dimensional views, an

existing version of the product, or prototype.

2) Take the assembly apart. Assign an identification number to each item as it

is removed. Initially, treat subassemblies as parts and then analyze

them as assemblies later.

3) Reassemble the product starting with the part having the highest

identification number. As each part is added to the assembly, analyze its

ease of handling and insertion and use the three questions to decide if it is a

candidate for elimination or combination with other parts

4) Redesign the assembly using the insights gained from the analysis. Analyze

the new design by repeat ing step 1 through 4 and gage

improvements by comparing design efficiencies between current and

modified design. Iterate until satisfied.

7

The Boothroyd and Dewhurst DFA analysis is basically completed in 6 steps.

The flow chart of Boothroyd and Dewhurst DFA analysis is shows in Figure 2.1

(Boothroyd, et. al, 2002)

Figure 2.1: Boothroyd Dewhurst DFA analysis.

Source : Muhammad Faizal Bin Alias ,2007.

Design Efficiency

Total assembly time

Total operation time

Manual Insection

analysis

Design for manual

Assembly analysis

Theoretical minimum

number

Manual handling

analysis