PRODUCT SIMPLIFICATION DESIGN IMPROVEMENT BY USING

DFMA METHOD

TAN NI YEN

Report submitted in partial 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

JUNE 2012

vi

ABSTRACT

Design for Manufacturing and Assembly (DFMA) is a tool for designing or redesign

product. The advantage of DFMA is able to reduce manufacturing cost. The main

objective of this project is to propose a new design for price labeler. Apart from that, the

manufacturing cost, assembly cost and time are also analysed to support the

improvement. The analysed were carried out through dismantle a unit of product,

functioning of each component and 3D modelling using SolidWork software and lastly

is using DFMA design guidelines to generate a new design. The selection criteria for a

good design are based on manufacturing cost and assembly time. Finally, the chosen

design was proven meet all needed criteria by improving 16.29% of the design

efficiency. The existing product design efficiency is 26.62% and the new propose of

design is 41.26%. The labour cost also manages to reduce RM0.1940 per product. For

the Design for Manufacturing (DFM) part, the better manufacturing process chooses is

injection moulding and the material used is Thermoplastic. Since the material choose is

Thermoplastic, so will maintain the original material which is Acrylonitrile butadiene

styrene (ABS). In this study, the overall cost reduction for DFMA is RM0.19 per

product which is RM1.50 reduce to RM1.31, the percentage reduction is 12.67%.

vii

ABSTRAK

Deign for Manufacturing and Assembly (DFMA) adalah kaedah untuk mereka bentuk

produk atau rekan bentuk semula satu produk. Kelebihan DFMA dapat mengurangkan

kos pengeluaran. Objektif utama project ini adalan untuk mencadangkan reka bentuk

baru untuk Pelabel harga. Selain daripada itu, kos pengeluaran, kos pemasangan dan

masa juga dianalisis untuk menyokong peningkatan. Project ini dijalankan dengan

mengurangkan komponen dalam produk, mengenalpastikan fungsi-fungsi setiap

komponen, pemedelan 3D mengunakan perisian SolidWork and seterusnya

mengunakan garis panduan rekan bentuk DFMA untuk menghasilkan reka bentuk baru.

Kriteria pemilihan bagi reka bentuk yang baik adalah berdasarkan kepada kos

pembuatan dan masa pemasangan. Akhir sekali, reka bentuk yang dipilih telah

meningkat kecekapan rekanbentuk sebanyak 16.29%. Kecekapan reka bentuk produk

yang sedia ada adalah 26.62% dan reka bentuk baru adalah 41.26%. Kos buruh juga

berjaya mengurangkan sebanyak RM0.1940 bagi setiap produk. Bagi Design for

Manufacturing (DFM), proses pembuatan yang terbaik adalah acuan suntikan dan bahan

yang digunakan adalah termoplastik. Produk yang sedia mengunakan Akrilonitril

butadiena stirena (ABS) sebagai bahan, jadi reka bentuk baru juga akan mengunakan

bahan ABS. Dalam kajian ini, pengurangan kos keseluruhan untuk DFMA adalah

RM0.19 bagi setiap produk, kos bahan dapat mengurangkan dari RM1.50 kepada

RM1.31, pengurangan peratusan adalah 12.67%.

viii

TABLE OF CONTENTS

Page

EXAMINER APPROVAL FORM ii

SUPERVISOR’S DECLARATION iii

STUDENT’S DECLARATION iv

ACKNOWLEDGEMENTS v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS xv

LIST OF ABBREVIATIONS xvi

CHAPTER 1 INTRODUCTION

1.1 Introduction 1

1.2 Project Background 2

1.3 Problem Statements/Purpose of Studies 3

1.4 Objective of Studies 4

1.5 Scope 4

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction 5

2.2 Design for Manufacturing and Assembly(DFMA) 5

2.3 Design for Assembly(DFA) 8

2.3.1 Manual Assembly

2.3.1.1 Handing

10

10

2.3.1.2 Insertion 12

2.3.2 Assembly Efficiency 18

2.4 Design for Manufacturing(DFM) 19

2.4.1 DFM Techniques 20

1 × ENTER (1.5 line

spacing)

ix

2.5 Concurrent Engineering 23

2.6 Design for Assembly Method 26

2.6.1 Boothroyd-Dewhurst Method

2.6.1.1 Manual Assembly Procedure

2.6.2 Hitachi Assemblability Evaluation Method

2.6.3 Lucas Hull DFA Method

2.6.4 Comparison of DFA Methods

26

27

31

34

37

2.7 Previous Research 38

2.7.1 Cost Reduction Study of Automotive Part Using DFA

Method: Headlamp by Farhan Bin Abdul Razak (2010)

38

2.7.2 DFMA Application on the Development of Parts For the

White Goods Industry by Canciglieri And Kovalchuk (2006) 38

2.7.3 Concurrent Engineering Approach in Designing Pressure

Vessel by Ismail

39

2.7.4 Redesign of Takada Radio Using Boothroyd Dewhurst

DFA Method by Mohamed Kader Maidin

39

CHAPTER 3 METHODOLOGY

3.1 Introduction 40

3.2 Design of the Project Study 40

3.3 Framework of the Study 42

3.3.1 Identifying and Selection of Product 42

3.3.2 Parts Disassemblies 42

3.3.3 Measuring and CAD Modeling 43

3.3.4 Boothroyd-Dewhurst DFA Manual Evaluation 43

3.3.5 Boothroyd-Dewhurst DFM Evaluation 50

CHAPTER 4 DESIGN EVALUATION AND MODELING

4.1 Product Specification 53

4.2 Product Tree of the Price Labeler 54

4.3 Part List Of the Original Design 55

4.4 4.2.1 Current Design Analysis Boothroyd-Dewhurst DFA Analysis 70

4.4.1 Boothroyd-Dewhurst Worksheet Analysis for the Original

Design

71

4.4.2 Estimation of Assembly Cost for the Original design 74

4.4.3 Design Efficiency for the Original Design 76

4.5 Product Redesign Evaluation 77

x

4.5.1 Generate New Design 77

4.5.2 Boothroyd-Dewhurst Worksheet Analysis for The New

Design

81

4.5.3 Estimation of Assembly Cost for the New Design 83

4.5.4 Design Efficiency for the New Design 85

4.6 New Design for DFM Analysis 86

4.7 Comparison Between Original and New Design 88

4.7.1 Total Cost for Three part of Original Design 90

4.7.2 Total Cost for Three parts for New Design 90

4.8 Analysis of Side Cover with the Snap Fit 92

4.9 Summary 96

CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS

5.1 Conclusion 97

5.2 Recommendations and Future Work 98

REFERENCES 100

APPENDICES 102

A1 Gantt Chart for Final Year Project 1 103

A2 Gantt Chart for Final Year Project 2 104

B1 Capabilities of a Range of Manufacturing Process 105

B2 Continue 106

B3 Continue 107

B4 Continue 108

B5 Shape Generation Capabilities of Processes 109

B6 Manufacturing Process and Material Selection 110

C1 BDI Assembly Manual Handing Time 111

C2 BDI Manual Assembly Insertion Time 112

D1 Result of the Shape Generation Capabilities of Processes 113

D2 Result of the Manufacturing Process For 3 Part of

Redesign

114

xi

LIST OF TABLES

Table No. Title Page

2.1 Alternative Fastening Arrangement 9

2.2 DFA Methods Comparison Table 37

3.1 Table for Computation of Design Efficiency 45

4.1 Price Labeler Specification 53

4.2 The Parts List for the Original Design 55

4.3 Part Specification 56

4.4 Design for Assembly (DFA) Worksheet for Original Design 71

4.5 Original Design for Cost Estimates of Price Labeler 74

4.6 Description and Modification of Base Plate Cover with The

Stamped Price Label Feeder Roller Holder.

77

4.7 Description and Modification of Base Cover Clip and The Side

Cover

78

4.8 Description and Modification of Side Cover Left and Right 80

4.9 Design for Assembly (DFA) Worksheet for New Design 81

4.10 New Design for Cost Estimates of Price Labeler 83

4.11 Result of DFM Analysis 86

4.12 Different Between Thermoset and Thermoplastic (BUSE) 86

4.13 Comparison Between the Previous and New Design in term of

Number of Component, Operating Time, Labour Cost and Design

Efficiency by Using DFA Method.

88

4.14 Comparison Between The Previous and New Design in term Of

Mass, Weight And Total Cost by Using DFM Method.

89

xii

LIST OF FIGURES

Figure No. Title Page

2.1 Time to Deliver Comparison Between DFMA + Concurrent

Engineering (CE) and The Traditional Methods.

(Joao Pedro, 2006)

6

2.2 “Over The Wall Design”. (G.Boothroyd, 1992) 7

2.3 Geometrical Features Affecting Part Handing. (Boothroyd, 2002). 10

2.4 Some Other Features Affecting Part Handling (Boothroyd, 2002). 11

2.5 Incorrect Geometry can Allow Part To Jam During Insertion.

(Boothroyd, 2002).

12

2.6 Provision Of Air-Relief Passages To Improve Insertion Into Blind

Holes. (Boothroyd, 2002)

12

2.7 Design For Ease Of Insertion- Assembly of Long Stepped Bushing

into Counter-Bored Hole. (Boothroyd, 2002).

13

2.8 Provision of Chamfers To Allow Easy Insertion. (Boothroyd, 2002). 13

2.9 Standardize Part (Boothroyd, 2002). 14

2.10 Single-Axis Pyramid Assembly (Boothroyd, 2002). 15

2.11 Provision of Self-Locating Features To Avoid Holding Down and

Alignment. (Boothroyd, 2002).

15

2.12 Design To Aid Insertion (Boothroyd, 2002). 16

2.13 Common Fastening Methods (Boothroyd, 2002). 16

2.14 Insertion from Opposite Direction Requires Repositioning of

Assembly (Boothroyd, 2002).

17

2.15 Manufacturing Process (I. Ferrer, 2010) 20

2.16 Concurrent Engineering As Expressed By Prime European Region.

(Sohlenius, 1992)

23

2.17 Toolkit Software Modules (Boothroyd, 2002) 26

2.18 Stages of Analysis (Boothroyd, 2002) 27

xiii

2.19 Effect of Part Thickness on Handling Time. (Boothroyd, 2002) 28

2.20 Alpha and Beta Rotational Symmetries for Various Parts.

(Boothroyd, 2002)

29

2.21 Features of Hitachi Assemblability Evaluation Method (AEM)

(Ohashi et al., 1985)

31

2.22 Example of The AEM Symbols and Penalty Scores. (Whitney, 2004) 32

2.23 Assemblability Evaluation and Improvement Example (G.Boothroyd,

1992)

33

2.24 Methodology of the Lucas Hull DFA Method 35

3.1 Part Size (Boothroyd, 2002) 43

3.2 Alpha Beta Assembly Angles (Boothroyd, 2002) 44

3.3 Stamper Price Label Feeder Roller 46

3.4 Result of Handing Time for Stamper Price Label Feeder Roller 47

3.5 Result of Insertion Time for Stamper Price Label Feeder Roller 48

3.6 Framework of The Study

52

4.1 Price Labeler Photo

53

4.2 Product Tree of Price Labeler Original Design. 54

4.3 Part Redesign for Base Plate Cover with The Stamped Price Label

Feeder Roller Holder.

77

4.4 (i) Original Part of the Base Cover Clip and the Side Cover

(ii) New Design Part of the Side Cover

78

78

4.5 (i) Part Redesign for Reducing the Screws

(ii) Part Redesign for Snap Fit

(iii) Assembly Part for Side Cover Left and Right

79

79

80

4.6 Sample Calculation of XXX Company’s Saving Cost Per Year

91

4.7 Tension Force Applied on the Surface of Side Cover (-500N)

92

4.8 Result of Tension Force Analysis

93

4.9 Compression Force Applied on the Surface of Side Cover (500N)

94

xiv

4.10 Result of Compresion Force Analysis 95

xv

LIST OF SYMBOLS

Ema Design efficiency

Nmin Theoretical minimum number of parts

Ta Basic assembly time = 3 second

Ed Functional efficiency

Tma Estimated time to complete the assembly of the product

Ed Functional efficiency

xvi

LIST OF ABBREVIATIONS

DFA Design for Assembly

DFM Design for Manufacture

DFMA Design for Manufacture and Assembly

CE Concurrent Engineering

PTFE Polytetrafluoro ethylene

AEM Assemblability Evaluation Method

CAE Computer-aided engineering

CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION

Design for Manufacturing and Assembly (DFMA) method is introduced by

Geoffrey Boothroyd since 1960s on automatic handling. The method of Design for

Manufacturing and Assembly (DFMA) can be used to redesign a product. DFMA is the

combination between Design for Manufacturing (DFM) and Design for Assembly

(DFA). DFM is manufacturing of individual component parts of a product or assembly

while DFA is addition or joining of parts to form a complete product. DFMA can help

us to simplify the product structures, reduce the assembly and manufacturing costs and

assembly time. By using this method, the quality of existing product can be improved

and cost can be reduced.

The main activities of the DFMA are concurrent engineering to provide

guidance to design team in simplifying the product structure, to reduce manufacturing

and assembly costs and to qualify improvements. Besides, it is also used as a

benchmarking tool to study competitors’ products, and as a should-cost tool to negotiate

contract with the supplier.

Basically, the objective of this study is to redesign a new selection of products

for a better design and lower production cost. Hence, the DFMA method has been

applied to analyse the original product (Price Labeler). DFMA is used to make a new

design which can reduce the assembly costs, material cost, time and increase design

efficiency. Lastly, in this chapter, the overall thesis outline is reviewed and discussed in

general.

2

1.2 PROJECT BACKGROUND

Original DFA method development stemmed from earlier work in 1960s on

automatic handling. In 1988, Ford Motor Company has applied this method to help the

company to save a billion dollars of capital and improve the design efficiency. Because

of the effectiveness of the DFA method, General Motor also becomes one of the leading

users of DFMA. Besides automatic handing sector, DFMA is also applied in industry

sector, medical, aerospace, manufacturing equipment, etc. Although its benefits used in

some company, but some of the company still could not implement the DFMA method.

The focus of DFMA is to help the design team to simplify the product structure,

improve the design quality, reliability, minimize the assembly and manufacturing costs,

and other cost sources are considered, as well as to encourage the spirit of team work

among designers. Teamwork is very important to a group of team members; they can

discuss the problem facing and solve it together (Luo, 2007). On the other hand, DFMA

is also important to study competitors’ products and processes from a design, quality,

material selection, number of components, manufacturing method, point of view and

then evaluate assembly or manufacturing difficulties in an effort to design a superior

product based upon the results of this detailed analysis.

Nowadays, there are many types of price labeler available in the market, but the

cost of design is too high for users, it needs a lot of improvement in terms of design and

assembly time. So, DFMA can help to improve the design efficiency, cost and

customers’ need. In this study, the requirement is the parts function have to be same as

the original when redesigning the parts; Thus, this study is able to expose to the field in

calculating the current design efficiency of the price labeler and the modification of the

current design by eliminating and simplifying some of the part to achieve a better

design and convenient to the users.

3

1.3 PROBLEM STATEMENTS/ PURPOSE OF STUDIES

Price labeler recently has become a very common product in our daily life

especially for shopkeepers. Price labeler is a common product, but the price is not

affordable for small shopkeepers. Manually labeling price tag by using hand will waste

time. Hence, product life volume must be high in this product to fulfil the requirement

of the user.

The purpose of this study is to redesign a price labeler to improve in term of

product design and optimization in assembly and manufacturing process for a

production. Basically, there are a lot of designs ready in the market but there are no fix

designs and they consist of many components and parts. When need to service, it is very

difficult to assemble which means it takes more time to be assembled. Therefore, a

simplified design of the price labeler will bring more advantages towards the company.

As a conclusion, Boothroyd-Dewhurst method is applied to redesign and

reconstruct to produce a higher quality and lower cost of production. This method can

reduce manufacturing and assembly cost, improve the quality of the production and

simplifying the product structure. Furthermore, continue development will produce

higher technology in manufacturing industry in our country.

4

1.4 OBJECTIVES OF STUDIES

The objectives of this study are:-

(i) To propose and improve design for price labeler.

(ii) To analyse and improve the product design efficiency.

(iii) To reduce the manufacturing cost for price labeler.

1.5 SCOPES

The scopes of this project are:-

(i) Price labeler MOTEX (MX5500) as the product for this project.

(ii) Boothroyd-Dewhurst DFMA is selected as the DFA tool.

(iii) SolidWork software as modelling drawing of the current product.

(iv) Literature review on product improvement using DFMA

approaches.

(iv) Apply DFMA methodology to identify design problems and

generate remedial design solutions.

CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

This chapter discusses about the following sub-chapters; design for

manufacturing and assembly, theory of inventive problem solving, review on previous

case studies and perspective approach.

2.2 DESIGN FOR MANUFACTURING AND ASSEMBLY (DFMA)

DFMA is a method to improve the adaptability and efficiency during times of

change. This idea can effort the use of the experience of previously done mistakes to

speed up the development process and also accomplish new technologies and

philosophies to ensure that activities which more faster and give more precise results

that can really reach this target (Pedro, 2006). DFMA is a combination between Design

for Manufacturing (DFM) and Design for Assembly (DFA). DFM is manufacturing of

individual component parts of a product or assembly while the DFA is the addition or

joining of parts to form a complete product (Boothroyd, 2002). Figure 2.1 show the

comparison between the DFMA and the traditional method which used before the

DFMA has been developed.

6

Figure 2.1: Time to Deliver Comparison between DFMA + Concurrent Engineering

(CE) and the Traditional Methods

Source: Pedro (2006)

According to Boothroyd (2002), it is about twenty years he have been working

in the area of product design manufacturing and assembly (DFMA), it have been

developed and discovered applied in industry—particularly U.S. industry. In fact, it can

be said that the availability of these methods have created a revolution in the product

design business and helped to break down the barriers between design and manufacture;

it has also allowed the development of concurrent or simultaneous engineering.

Guidice (2009) said that DFMA is a method to analysis and improvement of the

existing product, again implemented in commercially available computer software.

DFMA developed is possible to optimize manufacturing’s cost, invent a most efficient

and economical product. It also allows the analysis of each individual’s component and

its assembly in order to define the optimal solutions, facilitating the assembly of

subsystems and of the final product. From Boothroyd (2002) said, in the earliest stage,

DFMA is able to estimate both assembly and part of manufacturing cost.

7

DFMA would be a workstation-like environment at which a designer could

create a design in terms beyond just geometry, and accessing to capabilities for design

trade-off studies, cost reduction studies, producibility evaluations, design rule checking,

and manufacturing and assembly evaluations and recommendations. It will act like a

manufacturing expert looking over the designer's shoulder, providing a god suggestions,

comments about the design and the defect of the design pattern, and information about

fabrication and assembly (De Fazio T. L., 1993).

Tianhong Luo (2007) said DFMA is a methodology, this method can improve

the integration between designer and manufacturer, speed up the productivity cycle,

reduce the cost, improve product quality and reliability, to shorten lead time, to increase

productivity and fulfil the customer’s requirements. Hence, DFMA is a method to

reduce the design and assembly cost to simplify the structure of the product, improve

the quality and reliability to compare with the existing product. This method must be

done at the earliest state to avoid from the overhead cost under the consideration of

design team, the spirit of the co-operation is very important in this process.

Figure 2.2: “Over the Wall Design”

Source: Boothroyd.G (1992)

8

"We design it, you build it." This attitude has now become known as "over-the-

wall" design which means the designer did not care about the manufacturing engineer,

they think that their responsibility is to draw and design the drawing then after that

throw all the drawing to aside for manufacturing engineer. They are facing a lot of

manufacturing problem because they were not involved in design effort (Boothroyd.G,

1992).

2.3 DESIGN FOR ASSEMBLY (DFA)

Design for Assembly (DFA) has been taking seriously in early 1960s. The

development of this method is to work and overcome benefit to the company who using

this method (Boothroyd, 2002).

DFA method should be carefully considered at all stages of design in the early

stages so that can estimate the cost and time properly. The team design should provide

quick results and to simplify so that they are easy to use. It also should ensure

consistency and completeness in its evolution of product assembility. Beside this,

communication is very important for manufacturer and designer engineer, so it should

be improved. The idea, reasoning and decision made during the design process become

well documented for future references (Boothroyd, 2002; Pedro, 2006). DFA is the

design of the product for ease of assembly; it is using a systematic procedure step by

step to estimating assembly time and cost in the early stage. Teamwork is very

important for the designer and manufacturer to consider together to the structure of the

product, the purpose is to make adjustment to the design or parts and they will get a

immediate feedback of the effect of such change (Geng, 2004).

The objective of DFA method for these parts in a design is guiding the designer

to simplify the structure through combinations of parts or features, alternative choices of

securing methods or spatial relationship changes. Providing a tool for the designer team

to assists in the determination of the most efficient fastening methods for necessary

interfaces between separate items in a design. This is an important consideration since

separate fasteners are often the most labour intensive group of items when considering

mechanical assembly work. Consideration of the fastening method is very important

9

because 47% of assembly time is spent on the insertion and tightening of separate screw

and nuts (Geng, 2004).

Method Assembly time (s)

Snap Fit 4.1

Press Fit 7.3

Integral Screw Fastener 11.5

Rivet (4) 36.1

Machine Screw (4) 40.5

Screw/ Washer/ Nut (4) 73.8

Table 2.1: Alternative Fastening Arrangement

Source: Geng (2004)

In addition, the another objective is when starting to design something, the

senior designer will collect all the information about the design structure and arrange it

properly for junior designer engineer and estimate the assembly time, cost and the factor

which will cause the defect. Then they continue the procedure step by step. So that

overhead cost will not happen (Boothroyd, 2002).

Boothroyd Dewhurst DFA method is providing three criteria to give guidance to

the designer in reducing the part count, if the part does not satisfy at least one of these

three criteria, then it is considered to be a candidate for eliminate. The three criteria

(Boothroyd, 2002) are: -

(i) The part move relative to all other parts already assembled

(ii) The part be a different material than or be isolated from all other parts

already assemble.

(iii) The part be separated from all other parts already assembled because

otherwise necessary assembly or disassembly.

*Therefore none of the three criteria are met and the strap becomes a candidate for

elimination. For the strap a zero is placed in the column for minimum parts.

10

2.3.1 Manual Assembly

The process of manual assembly can be divided into two separate areas. Those

are handing and insertion (Boothroyd, 2002; Geng, 2004).

2.3.1.1 Handing

Handing is including the acquiring, orienting and moving the parts. In general,

for case of part handing, a designer should attempt to:

Figure 2.3: Geometrical Features Affecting Part Handing

Source: Boothroyd (2002)

Manual Assembly

Handing Insertion

11

Figure 2.4: Some Other Features Affecting Part Handling

Source: Boothroyd (2002)

i. Design parts that have end-to-end symmetry and rotational symmetry about

the axis of insertion. If this cannot be achieved, try to design parts having the

maximum possible symmetry (see Fig. 2.4a).

ii. Design parts that, in those instances where the part cannot be made

symmetric, are obviously asymmetric (see Fig. 2.4b).

iii. Provide features that will prevent jamming of parts that tend to nest or stack

when stored in bulk (see Fig. 2.4c).

iv. Avoid features that will allow tangling of parts when stored in bulk (see Fig.

2.4d).

v. Avoid parts that stick together or are slippery, delicate, flexible, very small,

or very large or that are hazardous to the handler (i.e., parts that are sharp,

splinter easily, etc.) (see Fig. 2.5)

12

2.3.1.2 Insertion

Insertion is mating a part to another part or group of parts. For ease of insertion a

designer should attempt to (Boothroyd, 2002).

Figure 2.5: Incorrect Geometry can Allow Part To Jam During Insertion

Source: Boothroyd (2002)

Figure 2.6: Provision of Air-Relief Passages to Improve Insertion into Blind Holes

Source: Boothroyd (2002)