Analysis of Assembly Line Balancing in Garment Production by Simulation

Analysis of Assembly Line Balancing, in Garment Production by Simulation

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Association

of Universities for Textiles

E-TEAM European Masters in Advanced Textile Engineering

"Analysis of Assembly Line Balancing in Garment Production by Simulation”

In the context of Lean Manufacturing and the TPS

Lina Katharina Rambausek

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Abstract

Subject of this dissertation is the analysis of assembly line balancing in garment production by simulation Aspects of Lean Manufacturing (LM) and the Toyota Production System (TPS) will be discussed in reference to the simulation experi-ments The analysis is accomplished with help of a simulation program, “Enter-prise Dynamics” The thesis is developed in connection to the master study pro-gram “European Masters in Advanced Textile Engineering” which is organised by the “Association of Universities for Textiles” (AUTEX)

The results are based on primary research and knowledge that was gained mainly during the stay at the Technical University Istanbul, Turkey, as well as on field trips

to companies in the sector of garment production The dissertation highlights weaknesses and constraints in the application of simulation programs concerning garment production It further explores the opportunities a simulation program could offer European manufacturers in order to stay competitive

Also in the textile sector, best practices as they are applied at other producing companies should be considered, and seen as benchmark According to Jeffrey K Liker (2004)1 the Japanese car manufacturer Toyota had it’s origin in the textile sector, the weaving industry It stands to reason that the ideas of the car manufac-turing system today could be applied by the way of knowledge transfer to fields of textile production This thesis will focus on the idea of LM (Lean Manufacturing) as well as on the strongly connected TPS (Toyota Production System)

The outcomes of this dissertation is intended to give applicants of simulation grams in the textile field an overview about the options to improve their business with simulation It will focus on opportunities and constraints of using a simulation program within the application of production line balancing

pro-Keywords: Line Balancing, Garment Manufacturing, Simulation Software,

Enter-prise Dynamics, Lean Manufacturing, Toyota Production System

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Table of Content

ABSTRACT I

TABLE OF CONTENT II

LIST OF ILLUSTRATIONS VI

LIST OF TABLES VIII

LIST OF EQUATIONS X

LIST OF ABBREVIATIONS XI

PREFACE XII

DECLARATION XIII

SUMMARY XIV

1 INTRODUCTION 1

2 OBJECTIVES 6

3 APPROACH 7

4 THE MANUFACTURING CONCEPTS 9

4.1 Progressive Bundle System (PBS) 9

4.1.1 Concept 9

4.1.2 Advantages of PBS 9

4.1.3 Disadvantages of PBS 9

4.2 Modular Manufacturing (MM) 10

4.2.1 Concept 10

4.2.2 Advantages of MM 11

4.2.3 Disadvantages of MM 12

4.3 Lean Manufacturing (LM), 12

4.3.1 Concept 13

4.3.1.1 Pull system 13

4.3.1.2 One-piece flow 14

4.3.1.3 Value-added ratio 14

4.3.1.4 Handling reduction 16

4.3.1.5 Single minute exchange of die (SMED) 16

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4.3.1.6 Standard work 16

4.3.1.7 Takt time 16

4.3.1.8 Line balancing 16

4.3.1.9 Productivity 17

4.3.1.10 Flow velocity 17

4.3.2 Advantages of LM: 17

4.3.3 Disadvantages of LM 18

4.3.4 Toyota Production System, 18

4.4 Mixed Manufacturing Module Design - Hybrid Version 21

5 ISTCOMP 22

5.1 Data base 22

5.2 Product 22

5.3 Layout 23

5.3.1 Section I & II in detail 29

5.3.2 I Body - Subassembly 30

5.3.3 II Collar and Lining Subassembly 34

5.3.4 Section III.& IV in detail 38

5.3.5 III Sleeve Subassembly 39

5.3.6 IV Final Assembly 41

5.3.7 Workforce 45

5.4 The work flow 49

5.5 Time Studies 55

6 LINE BALANCING 59

6.1 Line Balancing in general, 59

6.2 Line balancing at HUGO BOSS 66

6.2.1 Introduction 66

6.2.2 Production site 66

6.2.3 Workforce 67

6.2.4 General system of planning: 67

6.2.5 Efficiency 69

6.2.6 Special conditions in Dynamic lines 73

6.3 Simulation 74

6.4 Line Balancing in garment production 75

7 SOFTWARE ENTERPRISE DYNAMICS, 77

7.1 Application,,, 77

7.1.1 Model 77

7.1.2 Simulate 78

7.1.3 Visualize 78

7.1.4 Control 78

7.2 User 79

7.3 Data 82

8 SIMULATION MODEL 83

8.1 Simplifications 83

8.2 Aspects of Lean Manufacturing 84

8.3 Setup process 85

9 EXPERIMENTS 93

9.1 Experiment A0 97

9.1.1 Results of experiment A0 97

9.2.1 Improvement strategy - Experiment A1 99

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9.2.2 A1 Changes 101

9.3.3 Results of Experiment A2: 106

9.6 Overview experiment A 109

9.6.1 Output 110

9.6.2 Takt time 111

9.6.3 Number of operators 112

9.6.4 Productivity per operator 113

9.6.5 Average content in subassembly queues 114

9.6.6 Average stay time of the product in the queue 116

9.6.7 WIP values 119

9.6.8 Throughput time 120

9.7 Experiment B 121

9.8 Experiment B1 121

9.8.1 Improvement strategy - Experiment B1 121

9.8.2 B1 Changes 121

9.8.3 Results of experiment B1 124

9.9 Experiment B2 124

9.9.1 Improvement strategy - Experiment B2 125

9.9.2 B2 Changes 125

9.9.3 Results of experiment B2 126

9.10 Overview experiment B 127

9.10.1 Output 127

9.10.2 Number of Operators 128

9.10.3 Productivity per operator 130

10 CONCLUSION 133

10.1 Strengths 133

10.2 Weaknesses 134

10.3 Opportunities 135

10.4 Threats 135

10.5 Personal problems of the author 136

10.6 Future outlook 137

A APPENDIX A 139

A.1 List of minimum wages by country 139

B APPENDIX B 141

B.1 Data Basis – Machinery 141

C APPENDIX C 147

C1 ED System requirements: 147

D APPENDIX D 148

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D1 Simulation Model Layout 148

E APPENDIX E 149

Overview experiment A 149

E1 Output of the sections individually 149

E2 Number of operators per section 150

E3 Number of operators per section 152

F APPENDIX F 154

Overview experiment B 154

F1 List of operators and their assignments to servers according to Layout of ISTCOMP 154 BIBLIOGRAPHICAL REFERENCES 156

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List of Illustrations

Fig 3-1 Procedural method 8

Fig 4-1 Value added vs Non-value-added activities 15

Fig 4-2 Potential effect on Lead time after reducing non-value-added activities by 50% 15

Fig 4-3 Decision tree for evaluation of processes 20

Fig 5-1 Ladies’ jacket basic model 23

Fig 5-2 Drawing of ladies’ jacket production line (sections I & II) 24

Fig 5-3 Advanced sketch of the production line (all sections) 24

Fig 5-4 Layout ladies’ jacket production line, work flow at 22.02.2008 27

Fig 5-5 Layout ladies’ jacket production line, work flow at 22.02.2008 (part1/2) 29

Fig 5-6 Area which is worked-on in section I Body 30

Fig 5-7 Parts which are worked on in section II.C&L 34

Fig 5-8 Layout Ladies’ jacket production line, work flow at 22.02.2008 (part2/2) 38

Fig 5-9 Parts which are sub-assembled in section III 39

Fig 5-10 Parts which are assembled in section IV: 41

Fig 5-11 Number of workers I 46

Fig 5-12 Number of workers II 46

Fig 5-13 Average age of the workers 47

Fig 5-14 Average experience in this job 47

Fig 5-15 Number of operations the operators are trained-in 48

Fig 5-16 Work flow chart Ladies’ jacket production line, work flow at 22.02.2008 50

Fig 5-17 Work flow chart Ladies’ jacket production line, work flow at 22.02.2008 (part1/4) 51

Fig 5-21 REFA standard form for time studies 56

Fig 5-22 REFA standard form for time studies additional side 57

Fig 6-1 Work element sharing 63

Fig 6-2 Division of work element 64

Fig 6-3 Assembly sequence 65

Fig 6-4 Hierarchies at HB 67

Fig 7-1 Logo of the simulation software Enterprise Dynamics 77

Fig 7-2 VR-simulation of a warehouse system & a production line with the ED Logistic Suite 80 Fig 8-1 The layout of the simulation model 85

Fig 8-2 The atoms source, queue, server and assembler 86

Fig 8-3 Simulation model after the channels are connected 86

Fig 8-4 Simulation model after the channels are connected (more detailed) 87

Fig 8-5 Application of the values of operation 7 in “Stat:Fit” 88

Fig 8-6 Changing the atoms properties 90

Fig 8-7 After a test run of 90 hours the output volume is 7582 units 91

Fig 8-8 3D Model View after inserting the atom “VR building” 92

Fig 9-1 Experimentation Wizard 95

Fig 9-2 Experimentation Wizard, Performance Measures PFM 96

Fig 9-3 Library Tree ED 100

Fig 9-4 Status Monitor 100

Fig 9-5 Monitor 101

Fig 9-6 Output per shift of entire production line 110

Fig 9-7 Takt time of the entire production line 111

Fig 9-8 Total number of operators of the production line 112

Fig 9-9 Productivity per operator [units/operator] 113

Fig 9-10 Average content in the section’s queues 115

Fig 9-11 Average content in the section queue IIIb Sleeve Prep 116

Fig 9-12 Average stay time in the section’s queues 118

Fig 9-13 Average stay time in the section IIIb Sleeve Preparation Queue 118

Fig 9-14 WIP values of the entire production line according to values of A0 to A4 119

Fig 9-15 Throughput time of the entire production line according to values of A0 to A4 120

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Fig 9-16 Total output of the entire production line 127

Fig 9-17 Number of operators entire production line 128

Fig 9-18 Number of operators per section 130

Fig 9-19 Prodctivity per worker 131

Fig 9-20 Overview B - Productivity of operators per section 132

Fig B-1 Machinery at ISTCOMP within the sections I Body and II C&L 145

Fig B-2 Machinery at ISTCOMP within the sections III Sleeve and IV Assembly 146

Fig D-1 “Enterprise Dynamics” simulation model layout 148

Fig D-2“Enterprise Dynamics” simulation model layout with connections 148

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List of Tables

Table 4-1 Areas in which waste can be avoided 19

Table 5-1 Example: Code in section II Collar & Lining 25

Table 5-2 Example: Code in section II Collar & Lining 26

Table 5-3 Number of operations per section 28

Table 5-4 Operations of section I Body - Subassembly (part 1/4) 30

Table 5-8 Operations of section II Collar and Lining - Subassembly (part 1/4) 34

Table 5-12 Operations section III Sleeve Subassembly (part 1/2 39

Table 5-13 Operations section III Sleeve Subassembly (part 2/2) 40

Table 5-14 Operations of section IV Final Assembly (part 1/4) 41

Table 5-18 Number of workers per section 45

Table 5-19 Standard symbols determined by The American Society of Mechanical Engineers 49 Table 6-1 Example calculation 1 60

Table 6-2 Example calculation 2 62

Table 6-3 Example calculation 3 62

Table 6-4 Example: Operator A fulfils 4 different operations 71

Table 6-5 Line balancing sheet at HB 72

Table 7-1 Overview Application fields and clients 79

Table 8-1 Operations and their distributions (part 1/3) 88

Table 9-1 Output values experiment A0 98

Table 9-2 Input values experiment A0 98

Table 9-3 A1 - 1st Change - results gained through simulation 101

Table 9-4 A1 2nd Change - results gained through simulation 102

Table 9-5 Effect of the changes in experiment A1 102

Table 9-6 A2 1st Change - results gained through simulation 104

Table 9-7 A2 2nd Change - results gained through simulation 104

Table 9-8 A2 3 rd Change - results gained through simulation 105

Table 9-9 A2 4 th Change - results gained through simulation 105

Table 9-10 Effect of the changes in experiment A2 105

Table 9-11 A3 Changes- results gained through simulation 107

Table 9-12 A4 changes – Reduction in queue size 108

Table 9-13 A4 Change in WIP value 109

Table 9-14 A4 Change in Throughput time 109

Table 9-15 Overview experiment A – Output volume of the entire manufacturing line (1/2) 110

Table 9-16 Overview experiment A – Output volume of the entire manufacturing line (2/2) 110

Table 9-17 Overview experiment A – Takt time of the entire production line 111

Table 9-18 Overview experiment A – Number of operators of the entire production line 112

Table 9-19 Overview experiment A – Productivity of operators (output/no of operator) 113

Table 9-20 Overview experiment A – Average content in queue of section I Body 114

Table 9-21 Overview experiment A – Average content in queue of section II Collar & Lining 114 Table 9-22 Overview experiment A – Average content in queue of section III Sleeve 114

Table 9-23 Overview experiment A – Average content in queue of section IIIb Sleeve Prep 115 Table 9-24 Overview experiment A – Average stay time in queue of section I Body 116

Table 9-25 Overview experiment A – Average stay time in queue of section II Collar & Lining116 Table 9-26 Overview experiment A – Average stay time in queue of section III Sleeve 117

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Table 9-27 Overview experiment A – Average stay time in queue of section IIIb Sleeve Prep.117

Table 9-28 Overview experiment A – WIP values 119

Table 9-29 Overview experiment A – Throughput time of the production line 120

Table 9-30 Number of operators entire line 124

Table 9-31 Output entire line 124

Table 9-32 Number of operators of the entire production line 126

Table 9-33 Output volume of the total production line 126

Table 9-34 Overview B - Output of the entire production line 127

Table 9-35 overview B – Total number of Operators 128

Table 9-36 overview B – Total number of Operators comparison A0 to B2 128

Table 9-37 Overview B - Operator number within section I Body 129

Table 9-38 Overview B - Operator number within section IV Assembly 129

Table 9-39 Overview B – Productivity per operator entire production line 130

Table 9-40 Overview B – Productivity per operator entire production line, A0 vs B2 130

Table 9-41 Overview B - Productivity of operators in section I Body 131

Table 9-42 Overview B - Productivity of operators in section II C&L 131

Table 9-43 Overview B - Productivity of operators in section III Sleeve 132

Table 9-44 Overview B - Productivity of operators in section IV Assembly 132

Table A-1 Monthly gross minimum wage rates of an full-time adult employees aged 23+ [1] 139 Table B-1 Machinery at ISTCOMP 141

Table C-1 Hardware configurations 147

Table E-1 Overview experiment A – Output volume per shift section I Body 149

Table E-2 Overview experiment A – Output volume per shift section II Collar & Lining 149

Table E-3 Overview experiment A – Output volume Section III Sleeve 149

Table E-4 Overview experiment A – Output volume section IIIb Sleeve Preparation 150

Table E-5 Overview experiment A – Number of operators in section I Body and II C&L 150

Table E-6 Overview experiment A – Number of operators in section II C&L 150

Table E-7 Overview experiment A – Number of operators in section III Sleeve 151

Table E-8 Overview experiment A – Number of operators in section IIIb Sleeve Prep 151

Table E-9 Overview experiment A – number of operators in section IV Assembly 151

Table E-10 Overview experiment A – Productivity of operators per output value in section I 152

Table E-11 Overview experiment A – Productivity of operators per output value in section II 152 Table E-12 Overview experiment A – Productivity of operators per output value in section III.152 Table E-13 Overview experiment A – Productivity of operators per output value in section IIIb.153 Table E-14 Overview experiment A – Productivity of operators per output value in section IV.153 Table F-1 Assignment of operators to operations at ISTCOMP (part 1/2) 154

Table F-2 Assignment of operators to operations at ISTCOMP (part 22) 155

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List of Equations

Equation 1-1 Productivity 3

Equation 1-2 Labour productivity 3

Equation 1-3 Takt time 4

Equation 4-1 Lead time 14

Equation 4-2 Value added ratio 14

Equation 5-1 Average level of effort 57

Equation 5-2 Average of measure times 57

Equation 5-3 Standard time 57

Equation 6-1 Efficiency in line balancing 60

Equation 6-2 Idle time in line balancing 60

Equation 6-3 Demand for manpower 61

Equation 6-4 Group efficiency 69

Equation 6-5 Group performance 70

Equation 6-6 Personal efficiency 70

Equation 6-7 Personal performance 71

Equation 6-8 Output volume according to HB 72

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List of Abbreviations

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Preface

The dissertation is part of the two year postgraduate study program “European Masters in Advanced Textile Engineering” which is organised by the Association of Universities for Textiles The thesis was written in the final semester at the Techni-cal University Istanbul, Turkey

As of now, the use of simulation programs in production processes in the textile industry is rare Production planning is practical oriented, rather based on state of the art production planning techniques than on experience The advantages a simulation program could offer the user, are not widely known, so the interest in investing in new techniques, with an eye on time and money, is low The necessity

to improve the companies’ ways in production planning is often neglected An portant planning tool in production is line balancing In this paper, the technique of line balancing is combined with the use of a simulation program to show the pos-sibilities and constraints of simulation in production line balancing

Istanbul, Turkey, and Prof Mario de Araújo, University of Minho, Portugal

Specially mentioned should be besides several other companies I visited, the company Altınyıldız Mensucat ve Konfesiyon Fabrikaları A.Ş., Istanbul, where I was allowed to spend some weeks for time studies and research at the production site and HUGO BOSS AG, Izmir, where I had the chance to spend one week for research in state of the art production planning techniques at their plant in Izmir I would like to thank both companies for the cooperation and support during my stay

Special thanks to Mr C Enginar, who supported me during the work on my thesis, especially when it came to Turkish language skills

I would appreciate receiving the criticisms, corrections, and frank opinions of my readers

(Lina.Rambausek@gmx.de)

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Declaration

Herewith I declare that I have completed the present thesis by myself and without the use of any aids other than those listed All passages that were taken either directly or mutatis mutandis from published and non-published sources have been marked as such The thesis has not been submitted to a different examination au-thority in the same or similar form

consultation and to copy parts of the Master’s thesis for personal use Any other use falls under the limitations of the copyright, especially with regard to the obliga-tion of mentioning the source explicitly on quoting the results of this Master’s the-sis

The use of this paper regarding non-profit matters is without charge, a commercial use in opposite needs agreement with the author In addition, the author does not take any responsibility for the correctness of the information in this paper

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Summary

The dissertation has been written in the fourth semester of the study program

“European Masters in Advanced Textile Engineering”, organised by the tion of Textile Universities (AUTEX) It will evaluate the use of simulation software application in garment manufacturing industry with special reference to the use in production line balancing The usefulness of simulation software application in the context of line balancing in garment manufacturing industry is considered Addi-tionally, I shall ascertain whether or not this technique might be successfully ap-plied in garment manufacturing by conducting and observing a range of experi-ments

Associa-Chapter 1 will give an overview of the topic and establish why using simulation might be advantageous for textile companies Further on, chapter 2 will outline the aims and objectives of this dissertation and the 3rd chapter will address methodo-logical issues

In addition to simulation aspects, this paper will also examine issues concerning Lean Manufacturing and the Toyota Production System (TPS) A comparison be-tween manufacturing concepts is made in chapter 4 Here, the concepts of Pro-gressive Bundle System (PBS), Modular Manufacturing (MM), Lean Manufacturing (LM) and Mixed Manufacturing Module Design are discussed A detailed descrip-tion of the data base used for the experiments in further sections of this paper fol-lows in chapter 5 The data collection was undertaken on the shop floor of a ladies’ jacket production line in Istanbul The layout and the workflow of this particular line was analysed and time studies are made

Line balancing techniques are the topic of chapter 6 Here, information from state

of the art techniques in use is shown How the production lines at the company Hugo Boss in Izmir are balanced and general techniques for line balancing are described in detail Chapter 7 gives a presentation of the software “Enterprise Dy-namics” which is used for the construction of the simulation model in chapter 8 The chapter introduces us to current application fields of the software The con-struction method of the simulation model is explained in chapter 8 In addition to the setup process, this part deals with aspects of LM and degree of simplification regarding the simulation model

The experiments and its’ results are described closer in chapter 9 Six different experiments with each a different line balancing strategy are conducted The sec-tions 9.6 and 9.8 summarize the result of the experiments and the outcomes of the experiments are compared

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The conclusion in chapter 10 contains a SWOT analysis which describes

strengths, weaknesses, opportunities and threats of the application of simulation

software in garment production and line balancing Also future perspectives of the application are discussed

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1 Introduction

Worldwide competition as part of the process of globalisation challenges garment manufacturers in Europe The considerable pressure to outsource production be-yond the boarders of Europe increased with time To remain competitive, hence to sustain the option to produce in the western world, companies have to find their competitive advantages in production processes.2

The potential yield of a strategic business unit, consequently, can be determined

by the difference between price and unit costs which are based on value-adding and non-value-adding activities Therefore the value of the product is defined by all activities of the business unit

This paper focuses on the ratio between value-adding and non-value-adding tivities Those either accomplish to cost advantage by influencing the situation of costs of the business unit, or provide a basis for achievement in differentiation to the competitor

ac-According to Kutz, Zerres and Zerres, value-adding activities are those activities, which generate added value for the final customer and for which the customer is willing to pay Also, value-adding activities become comparative advantages in competition in terms of differentiation on the basis of costs3

Customers are not longer willing to pay for non-value-adding production esses Higher standards in quality and at the same time faster supply of products are demanded

proc-In modern markets, customers demand: 4

• The right product and its variations

Fashion trends are changing rapidly The producer has to deal with a high ability in quantity, that means decreasing contract size, as well as with high

vari-model diversity

• the best quality

As high-quality level and the best service are demanded, a need for more trol emerged

con-• at the time needed

The manufacturer should be able to handle quick delivery, thus ensures a short throughput-time at high productivity rates

• at a reasonable price

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The customer does not want to pay for things which do not add value to the product, e.g unnecessary transports

To not reduce costs of production on account of the quality, to meet the pressure

on productivity and the shifted customer demands, companies need to find ways

to increase efficiency in production by other means Time is a critical factor

save money and time in the production procedure is a key issue which is tackled

by various companies in a number of ways Some focus on radically changing the production system to cut costs, others on increasing productivity and enhancing

Clothing and textile production can be situated in less-developed countries bour-intensive but low-tech production methods contribute to the advantage in production costs In comparison, the necessity to decrease labour costs with high-tech like information technologies and automation becomes more apparent in de-

As mentioned, low labour costs, are besides other cost factors, a major reason why companies outsource production beyond the boarders of Europe Even if high labour costs in Europe are reasonable, to produce in a European country is an expensive business A list of gross minimum wage rates of countries textiles are also produced in is shown in Appendix A

Nevertheless, staying competitive, when producing garments in Europe, is of great importance Therefore the aim is to reduce the costs of labour per produced piece From history, it can be recognized that some companies tried to decrease these costs by reducing the number of employees but this is, on the long run, the wrong approach to the problem The past of developed countries as well as today’s de-velopment in China show that as manufacturing productivity accelerates, indus-tries loose jobs in manufacturing The rise in productivity comes from improved

force without labour replacement by technology attracts more and more notice

The better method to improve productivity is to use the available assets and force more efficiently “Increasing productivity”, is the new mantra and no stone is left unturned to improve processes in production and other business units

work-The term productivity has a number of different definitions In industry, it is most commonly used with labour efficiency In general productivity is the ratio of output and input

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outputty

Productivi =

Equation 1-1 Productivity9

Regarding labour, productivity may be defined as output per unit of time or output per labour hour; it directly contributes to the productivity of the firm as the author Mosser Barnes (1980) indicates.10

time

outputty

productivi

Equation 1-2 Labour productivity11

Of course besides effectiveness of labour, other factors like the efficient operation

of machines, equipment, facilities and the economical use of materials affect ductivity of the company and finally the production costs of the product

pro-As noted above, besides increasing labour productivity, also technological tion can be considered to improve overall productivity High tech-machines, auto-mated production, or transport systems can be introduced into the production process Introduction of high-tech machinery costs time and is a capital invest-ment, which in many cases the companies can ill afford

innova-The key is to start simple and investigate first the own production processes, to finally find the scope where easy and quick changes can save money, time or in-crease quality Many simple changes can sometimes exceed the success of a sin-gle complex one This issue directs us to the practices of the car manufacture Toyota and its production system TPS It should be mentioned that Toyota derived from a weaving company, hence the textile sector One important issue in the con-text of the TPS is the avoidance of waste in all production process steps The TPS

is a well-known and highly successive production system; it should be possible to apply the ideas within the system in garment and textile industry also To improve garment production the companies should investigate manufacturing processes from other fields and apply best practices from other industries, like car manufac-turing

Another approach to increase productivity is line balancing Line balancing loss is waiting time, which is caused by unbalanced or inadequate balanced production line, expressed in no of operators That means, periods when the operator waits for further work which is coming from workstations in the production line which works in sequential steps If the line is balanced well, the line balancing loss should be at a minimum Perfectly balanced lines with a line balancing loss of zero operators are unusual The calculation of Takt time helps the planner to schedule the work stations

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TimeTime

Takt =

If all workstations work with the same Takt time and there are no interruptions in production, then exactly one output unit is produced in the rhythm of Takt time For example, a company should produce 500 units per shift of 8 hours

unit

minutes

0,96units

500

minutes

From my experience and knowledge that I gained during my studies, it appears to

• In production, trial and error methods are still common which seems to lessen the degree of productivity which might be possible to achieve

• Companies remaining focussed on experience based knowledge which is hard to transfer to other employees for example in if employees need to be replaced

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More or less, still the system based on “experience based knowledge” works In case experience values get lost or can’t be developed further, production proc-esses in real life situations could be complicated to deal with In the textile sector

as in other producing industries, production planning tools are necessary to tain and to improve productivity which arguably is a competitive advantage

main-In other manufacturing industries, simulation of production processes is well lished Simulation is recognized as a powerful problem-solving tool which has its roots in hard systems engineering like car manufacturing In garment and clothing manufacturing the application needs to be more extensive as modelling human systems is more demanding and complex Consequently a range of simplifications have to be made to achieve a decrease in the complexity of human behaviour.13

estab-The rationale for this paper lies in the observations and experiences within ment manufacturing processes cited above

gar-Chapter 2 and 3 describe the objectives of this thesis as well as show the method completed in this thesis A literature review regarding manufacturing concept is given in chapter 4 The data base for construction the simulation in further chap-ters is discussed in chapter 5 Chapter 6 deals with the literature review concern-ing line balancing techniques The software used for the experiments in chapter 9

is described in chapter 7 Chapter 8 contains a case study which is built upon data gained during the research phase in this project The content of this paper deals with the topic production process, touches the matter of line balancing and the theme simulation Results of the empirical part of this work will be given in chapter

9 An overall evaluation of the application in line balancing in garment ing will be discussed in chapter 10

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manufactur-2 Objectives

Aim of this dissertation is to evaluate the use of simulation software in the process

of line balancing in garment manufacturing The information is intended to give users or future users of simulation software an overview of strengths and weak-nesses in this special case of application

Furthermore, this aims to make suggestions concerning possible problem tions during the first use of simulation software in line balancing The experimental approach in chapter 9, deals with several line balancing strategies

resolu-The main subject of this dissertation focuses on line balancing in the context of Lean Manufacturing, avoidance of non-adding value activities and constrains in the usage of simulation software in line balancing in garment production

Finally this paper is using SWOT analysis for the application of simulation software

in garment manufacturing in chapter 10 Advantages and Disadvantages of the application of simulation software in production line balancing will be addressed Users of the information offered in this thesis should be aware that circumstances

of different production sites, of course, change the requirements of the application

of the software The improvements within the experiments discussed are not the only solutions valid for all production environments Analysing a production proc-ess and building a simulation model go hand-in-hand with close investigation of the conditions at the manufacturing site Also, in order to avoid exceeding the scope of this dissertation, the model in this paper is based on a number of simplifi-cations, which will be explored later on The dissertation is written within confines

of the subject of textile technology and therefore is not intended to challenge ters of industrial engineering and programming

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mat-3 Approach

The aim of this paper is to evaluate application of simulation software when bined with the techniques of production line balancing The SWOT analysis is based on data collection on the production floor and through experimentation with the simulation model derived from the data Opportunities and constraints of the use of simulation software in the context of line balancing are highlighted Also problems in setting up simulation models in the mentioned context are presented Following aspects will be investigated during the use of the simulation model

com-• output units and productivity,

• status of the operator e.g busy or idle,

• number of units in inventory,

• utility values of the single operations

Of course, issues such as bottlenecks will be detected and analysed

The research plan is as follows:

1 Literature review and on-site research

2 Time studies

3 Work flow analysis

4 Simulation model set up

5 Simulation experiments with various techniques of line balancing

6 Evaluation of the usage of simulation software for the application in tion line balancing

produc-The actual procedural method to the final results in chapter 10, is shown in Fig 3-1

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Fig 3-1 Procedural method14

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4 The Manufacturing Concepts

Due to the tremendous increase in speed of fashion changes during the last ades, garment production is challenged by many influencing factors Besides variations in product style, in material and accessories, variations in order quanti-ties and quality aspects; the time to respond to the market can be the decisive fac-tor to the success as garment manufacturer in Europe Apparel manufacturers have to experiment with new manufacturing concepts to meet the demand of the market and hence, staying competitive Three important manufacturing methods are explained in the following sections They are developed consecutively in time and always build upon the previous manufacturing system According to this ap-proach, the mentioned advantages and disadvantages always refer to the previous concept

4.1.1 Concept

Each operator is assigned to only one machine, performing a single operation petitively Through the production line, the parts are passed on in bundles of for example 25 pieces per bundle

• Quality inspections are generally made at the end of the line At this point of the line, the repair can get more complex due to the whole garment needs

to be unpicked to rectify a fault made early in the production stage Hence, more time is needed for rework

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• Payment on production or piece rate means that intensive quality control is necessary The worker is incentives to speed up the production to generate

a higher output, on account of the product quality

• The level of flexibility is low It is not recommended producing small ties

quanti-• Generally large stock between the stations is built up The operational time

at different workstation varies; so either inventory is kept or operators might need to wait for pieces from previous slower work steps due to the bundle system

4.2 Modular Manufacturing (MM)

MM is one of the most popular concepts in garment production.∗ The MM concept

is similar to the Toyota Sewn System Manufacturing Module Design (TSS) of yoda, today car manufacturer Toyota

To-4.2.1 Concept16

All operators are cross-trained and handle several machines The operator works

in a predetermined section or zones of the production line, for example in a like arrangement The bundle size is one The worker is standing during fulfilling his task Due to the fact that in garment manufacturing most of the operations are fulfilled seated, this concept cannot be transferred one-to-one to apparel produc-tion systems

cell-The movement rules of the workers are as follows:

• Operator A works in a U-shaped manufacturing cell He moves with the product counter clock-wise and along with the production flow

• Operator A moves with the product within his cell as long as he does not reach the successive operator If operator A meets the operator B, B is tak-ing over the product moving with it in production flow direction

• Operator A, now without a product to work-on, moves against the tion flow in clockwise direction, till he reaches another product This product can be either waiting in a storage area or another operator (C) is working-

produc-on it

∗

The American Apparel manufacturing Association (AAMA) has defined modular manufacturing as:

“a contained, manageable work unit of 5-17 people performing a measurable task The operators are interchangeable among tasks within the group to the extent practical, and incentive compen- sation is based on the team’s output of first quality products.” (Gilbert 1989)

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• Operator A interrupts operator C and takes over the product at the station and again moves with it to the succeeding work step in production flow direction

work-• The movement is continued according to the rules described

Other worker movement rules are based on current WIP status in the production,

on push-and-pull aspects or the rabbit chase method In this context the tions mentioned will not be explained more detailed.∗

regula-4.2.2 Advantages of MM

• The operator is involved in the production of complete garments The tion between operator and product is emphasized; therefore the quality of each single product attracts more attention of the operator then in PBS In PBS the operator fulfils only a single operation in the production line

rela-• Variations in the working process enrich the job of the operator The tors are cross-trained and perform several sewing tasks

opera-• Quality inspection and rework can be assigned to a group of operators For example to a group which works in the same cell, team work is empha-sized; quality defects can be recognized earlier

• The interface with the management can be intensified through e.g group meetings Time for supervising and inspections can be reduced if done on a team basis

• Concerning payment terms, fixed salaries in combination with production bonuses can keep quality and production rates stable

• Throughput time and WIP are reduced which consequently reduces costs in production.17

• Through the bundle size of one piece, time for handing is reduced cantly

signifi-• Time the operator normally spends for waiting is decreased The worker can move against the direction of production flow to find parts to work on,

an increase in plant and worker productivity can be achieved

∗

Further details on operator movement with WIP, Rabbit chase and Push/Pull methods can be found in “A generic simulator for modeling manufacturing modules”, B.J Schroer, P.A Farrigton, J.J.Swain, D.R Utley, Proceedings of the 1996 winter Simulation Conference, p 1156 - 1158

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opera-• Ergonomic aspects are neglected; the workplaces within one zone should fit

to all operators within the area which is practically impossible The sation at the workstation can be deficient Also the conditions at the work-place can be inadequate, because responsibilities for maintenance of ma-chines are not clearly assigned to the operators

organi-• Due to increased speed in production the number of defects could rise

• Movement rules and time pressure; could cause the operator to feel surised; hence the operator is exposed to increased stress levels The product’s quality could fall

pres-• To prevent bottlenecks an increased number of machinery is needed Thus, the floor space has to be enlarged, too

• The training of the operators is more time intensive using MM in son with PBS, especially when it comes to new operators All operators of a cell team need to be able to fulfil all operations within the cell

compari-• When making changes in the production line, considerable supervisory planning is needed

Lean manufacturing was introduced to reduce the time to the market even more

LM derived from TPS (Toyota Production System) which was developed by yoda Motor Car Company, today known as Toyota Motor Corporation

To-Definition:

“a manufacturing system with extraordinary capability to meet the rapidly changing needs of the market place; a system that can shift rapidly among product model or between product lines, ideally in real-time response to customer’s demands” (Youssef, 1994)20

Here, the concept is explained in key words, further details on the most important aspects will be following in successive chapters

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4.3.1 Concept

• One-piece flow with pull system,

instead of batch production with

push system

• No inventory, KanBan

(Inven-tory control via card system), to

synchronize production to the

• Line optimization, Line

balanc-ing to prevent waitbalanc-ing operators

and overproduction

• Productivity and Total

productiv-ity maintenance (TPM)

• Poka Yoke (Mistake proofing),

Zero defect strategy

• Application of Kaizen, tinuous improvement) and Total Quality Management (TQM)

Em-• Value stream mapping, visual management

• Facility and Layout, prevent interruptions in production stream

• Customer driven, value should be rethought from the view point of the ultimate cus-tomer

• Perfection is focused not benchmarking with the com-petitors

4.3.1.1 Pull system

The pull system describes the relationship between single workstations in the duction line Successive workstations are treated like customers with demands Only if the consecutive station demands a part from the previous station for further processing, the part is delivered If there is no demand, the workstation stops pro-duction Hence, the building of stocks within the production line is prevented and waiting time is reduced to a minimum The procedure described is similar to the Kanban system in the TPS

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proc-Through Value-Stream-Mapping the value-adding activities can be easily detected

By subtracting the time value of those from lead time in production, the time which

is spend on non-value-adding activities can be calculated.21

activitiesadding

value -nonactivitiesadding

adding-

value

activities

addingvalue

nonratio-added

min-Calculation: Lead time = 6480 minutes,

Value-added activities = 195 minutes These values result in 6285 minutes of non-value-added activities

The value added ratio is 32/1

From this ratio it can be easily recognized that the production consists of 3,01% value-adding and 96,99% non-value-adding activities

The following example shall show the effect of a reduction in the value of value-added activities In this case the ratio between value-added and non-value-added is 19/1 The non-value-adding activities sum up to 95% in comparison to 5% value-adding activities See figure Fig 4-1

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non-Value-added vs Non-value-added activities

5%

95%

Value-added activitiesNon-value-added activities

Fig 4-1 Value added vs Non-value-added activities 24

The effects on lead time after reducing the non-value-added activities by 50% are visualized in Fig 4-2 As a result, the percentage of value adding activities would increase; the lead time would be about 48% shorter

Potential effect on Lead Time after reducting

non-value-adding activities by 50 %

5%

47%

48% Value-added activitiesNon-value-added activities

Lead Time Improvement

Fig 4-2 Potential effect on Lead time after reducing non-value-added activities by 50%25

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4.3.1.4 Handling reduction

Often, handling and transport of material are non-value-adding activities By ing the handling and transport time to a minimum, the productivity per operator and so the value-added ratio can be improved significantly A reduction in trans-port time can be easily achieved through clever layout planning

reduc-4.3.1.5 Single minute exchange of die (SMED)

Another important factor for keeping flexibility in production and reducing handling time is the time for setting up machines Small order sizes and numerous varia-tions in styles cause the operator to set up a machine several times a day To keep the time for the setup operation – a non-value-adding activity - at a minimum, SMED systems have to be developed

4.3.1.6 Standard work

Through applying standard work in the production line, the quality of the product and speed within the production line can be increased The speed rises because the optimal and fastest method to operate is determined by e.g method studies Also the quality is improved due to that all operator use the same method Both, quality and speed can be kept more constant during the production; planning and controlling the line are alleviated Defects and rework can be avoided

4.3.1.7 Takt time

The calculation of Takt time is based on the target production quantity per day and

on the standard time per operation

[ ]

units

min timeTime

be adapted to the output targets per time If the cycle times of the operations are equal Takt time, the production runs smoothly, if not the line needs to be balanced Line balancing is explained explicit in chapter 6

4.3.1.8 Line balancing

Line balancing is a tool for planning the amount of personnel needed for a certain production quantity The various methods for planning are explained in Chapter 6

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4.3.1.9 Productivity

The price per output unit is amongst other things determined by the productivity Particularly, in countries like Europe where high labour costs affect the overall production costs highly, the productivity of each single operator is significant Through good planning and application of high technology equipment productivity per operator can be improved easily

4.3.1.10 Flow velocity

The higher the speed within the production line, the shorter is the resulting throughput time This causes fast inventory turns; the final turnover is generated much quicker

4.3.2 Advantages of LM:

• Due to the bundle size of one, the WIP is kept at a minimum Waiting time between the workstations is reduced to zero; stocks within the production line are not built up

• Assuming stock is not kept within the line, the requirements for floor space

is less than in MM Also to reduce transport time within the production line the floor size of the layout should be minimized in

• The throughput time is reduced due to a low WIP

• Clear responsibilities ensure enhanced quality of the product According to that the operators are dealing only with few different operations, the training level of each operator is high The operator can fulfil his task optimally re-garding pace and quality Additionally, the regularity in maintenance of the equipment can be optimized when operators are assigned only to some machines

• The line can be balanced through the use of Takt time Each operator is signed to a certain number of operations When the durations of those op-erations are summed up, the value should equal the predetermined Takt time

as-For example, the operator is handling 3 operations which have a duration of

1, 0.6 and 0.4 minutes If the Takt time is 2 minutes this operator is not causing a bottleneck situation within the process The sum of the durations

of his operations exceeds the Takt time the operator is too slow, preceding work stations have to wait If the operational time under-runs the Takt time, inventory could be built up, LM prevents inventory so the operator has to be occupied with another task to keep production flow as smooth as possible

• Through time and motion studies the production can be planned even more efficiently

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4.3.3 Disadvantages of LM

• To meet Takt time specifications, more time for planning and control is needed Sometimes it is necessary to employ specialists to fulfil these tasks Also, it takes longer to train operators at several work stations and in distinct operations

• Once a layout for a production with respect to lean manufacturing aspects

is set up, the structure is more rigid than others This could cause problems when it comes to the flexibility of the system Rapidly changing styles or small order sizes can affect the efficiency of the layout For low volume and prototype production, or one-of-a-kind products, lean manufacturing produc-tion line setup is not suitable Best results with the lean manufacturing con-cept can be achieved in inflexible production processes like routine work

4.3.4 Toyota Production System27,28

A main issue in the TPS, besides the approach of LM, is the elimination of “Muda”, which translated from Japanese, means waste In this particular context manufac-turing Muda is concerned, or better the non-value-adding activities within the pro-duction process

There are 7 types of waste:

1 Waste from overproduction

2 Waste from waiting

3 Transportation waste

4 Processing waste (work steps which are not needed necessarily)

5 Inventory waste (also products that no-one wants)

6 Waste of motion, and

7 Waste from product defects (mistakes which require rework)

Waste most often concerns the waste of time in the production process Time is an unrecoverable resource, once spend it is not possible to recover it As with all re-sources the efficient use of time should be focussed

In the book “Lean Manufacturing for the Small Shop”, G Conner mentions that companies do not pay much attention to the prevention of waste He also gives the reason for this insensitivity in following quotation

“If wasting time would stink as garbage, people would certainly pay more attention to it.”

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The guideline to avoidance or reduction of waste concerns: activities, behaviours and conditions Some ways to prevent waste are shown in

Table 4-1 Areas in which waste can be avoided29

Areas in which waste

can be avoided : A solution concept could be:

Facility layout Considerable planning of the production line layout

mini-mizes transport ways and floor space

Excessive set-up time SMED and quick release tooling can save time in the

pro-duction process The cycle time can be reduced

Incapable process Method and time studies can help to find the optimum

responsibili-Uncontrolled work

method

To sustain quality, standards in work methods should be set up This could be done for example with Motion Time Measurement (MTM)

Lack of training Through regular training quality can be improved and the

defect rate is decreased

Lack of work place

organisation

Ergonomic and organisational aspects should be dressed when planning the workplace For example, the supply of trimmings should be continuous without waiting

ad-Lack of supplier

qual-ity & reliabilqual-ity

Evaluation of suppliers should be a continuous process A classification of suppliers according to their evaluation can avoid quality defect or shortages in production material

Lack of concern

(ac-countability)

The assignment of operators to machines generates a sponsibility for the equipment Also if operations are clearly assigned operators are more concerned with the quality of their work

re-Passing of defect parts Continuous control during the operation can prevent

de-fects Rework can be minimized

Lack of

communica-tion

Regular team meetings are a tool to support tion within the team Problems can be solved more effi-ciently through team work

communica-A way to detect waste within processes is Value Stream Mapping (VSM) VSM is a visual tool for identifying all activities in planning and production processes All business activities are shown in a detailed schema Through mapping of proc-

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esses, value adding or more important non-value-adding processes can be mined If the non-value-adding activity is arbitrary it should be eliminated to finally avoid waste Fig 4-3 shows a method to determine action if a non-value adding activity is detected

deter-Fig 4-3 Decision tree for evaluation of processes30

VSM also offers the user better process control and visibility, with the possibility to reduce lead times and costs, and to improve skills and technology which are all linked to the company’s competitive advantage.31The TPS enabled Toyota to syn-chronize their production volume with their sales and hence, the demand in the market.32

LM derived from the TPS, so many aspects are at least similar and will not be cussed here in detail

dis-Is the operation of value for the ultimate customer?

Yes No

Can the operation be eliminated completely?

Yes No

Eliminate process, range the production proc-

rear-ess

Is the process (still)

improv-able?

Yes No

Keep process

as it is

Change process, improve the production process

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4.4 Mixed Manufacturing Module Design - Hybrid Version

Of course, it is not always possible to clearly determine the production concept in use To meet order specifications and to optimise the production, a combination of manufacturing concepts might be necessary Order specifications change in time and from customer to customer; also, varying order volumes and variations in product styles are challenges the production line set-up needs to face

The main reason to develop a hybrid manufacturing concept is the flexibility in production More customers with varying specification can be served at once, si-multaneously or consecutively

An example:

The combination of LM and MM in one and the same production line can be ful Lean Manufacturing could be applied in the critical path of the production line, PBS or Modular Manufacturing in the supplying branches of the same This hybrid version guarantees the continuous supply of sub-assembled pieces through MM/PBS and perfectly balanced operations within the critical path according to

fruit-LM The critical path operations determine the throughput or output per day As long as these operations are fulfilled at optimum level, the maximum output per day can be achieved

To set-up a hybrid version of the manufacturing structure with different single lines,

a possible and common approach is to define the shares of the combination on basis of the sales volume

For example:

• Special cells: 15% of sales volume – prototype production, no concept termined because the line is too flexible

de-• Standard cells: 25% of sales volume – e.g LM

• Just-in-time (JIT) Cells: 60% of sales volume – e.g MM or LM

Another possible scenario are the 80/20 rule, 80% of production is adapted to the

“bread-and-butter” business the rest is adapted to just-in-case scenarios.33

Other hybrid versions are determined on basis of push- or pull strategy, where batch and lot size one can vary within the production line Also the assignment of workers to single or multiple operations can be an aspect, hybrids are set-up on Both, mass production customers, as well as customers for special manufacturing concerns can be served with hybrid systems Through the combination of manu-facturing concepts, the producer is not forced to an “either-or” decision which im-proves his competitive ability

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5 ISTCOMP

5.1 Data base

Further analysis is based on data gained in at a production site Due to reasons of privacy this company will further be called “ISTCOMP” Also time studies were car-ried out at this company in February and March 2008

ISTCOMP is situated on the European side of Istanbul close to the airport Over

1000 employees are working at this production site Besides the production of rics, ready-made clothing like suits, jackets and trousers are manufactured, either for own brands or order-based for various retailer brands

fab-The production floor consists of four production lines and a prototype production area The four lines are divided according to the garment produced in: Men’s jacket, Men’s trousers, Ladies’ jacket, and Ladies’ skirts and trousers I had the chance to analyse and to carry out time studies in the production line for Ladies’ jackets

The line for ladies’ jackets is divided into four sections:

5.2 Product

To analyse the production line of the ladies’ jacket, a particular jacket model was chosen To keep the complexity for simulation as low as possible, the analysis is based on a simple basic model lady jacket See (Fig 5-1)

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Fig 5-1 Ladies’ jacket basic model∗34∗

For the production of one of the chosen jacket model 85 individual manufacturing steps are needed When analysing the line, 96 operators were working in the pro-duction line production The analysis only focuses on the manufacturing steps; final ironing, buttoning of fronts, quality control, and of course packaging and shipment are not considered

5.3 Layout

To analyse the production line and to set up a workflow chart, the analysis was started from scratch Information was not or insufficiently available, only names of operations used within the line and old standard times were known As well, the list of operations had to be translated from Turkish to English first, so that at least the name of the operation was clear Later it was found out that even the men-tioned list of operations was not updated, so coming across operations which were changed or even new in this particular list was usual Of course, the sequence of operation within the production flow needed to be changed as well

At first, it was essentially to set up a layout plan to get to know the product better,

to see how the production is running through the line and to check against the list

of operations supplied by ISTCOMP

As mentioned, starting point was a drawing of the production line from scratch This drawing contained ways of transport and at first resulted into a “spaghetti dia-gram” which showed all movements of the material The diagram is shown in Fig 5-2 and Fig 5-3

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Fig 5-2 Drawing of ladies’ jacket production line (sections I & II)35

Fig 5-3 Advanced sketch of the production line (all sections) 36

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