A STUDY OF FLEXIBLE MANUFACTURING SYSTEM

IN CIMS CONTEXT

by

MOHAMMED ALI

Department of Mechanical Engineering

Submitted

in fulfillment of the requirements of the degree of Doctor of Philosophy

to the

Indian Institute of Technology, Delhi

May, 2006

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Certificate

This is to certify that the thesis entitled ,A Study of Flexible Manufacturing

System in CIMS Context' submitted by Mohammed Ali to the Indian Institute of

Technology, Delhi, India, for the award of degree of Doctor of Philosophy, is a record

of bonafide research work carried out by him under our supervision and guidance. The

results obtained in this thesis have not been submitted to any other University or

Institute for the award of any degree or diploma.

Dr. Subhash Wadhwa Professor Deptt.of Mechanical Engineering Indian Institute of Technology, Delhi New Delhi-110016

Dr. P.V. Rao Associate Professor Deptt.of Mechanical Engineering Indian Institute of Technology, Delhi New Delhi-110016

Dedicated to my loving Parents

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Acknowledgement

At the very outset I would like to thank the Almighty Allah, for giving me the

strength to complete this task.

This thesis could not have been written without the support of many persons,

and I now would like to thank those who have in one way or another contributed to

this thesis.

I take this opportunity to express my gratitude to Prof Subhash Wadhwa, my

PhD supervisor at IIT, Delhi. His commitment, interest, and passion for the research

have always been undiminished, and it is difficult to imagine how I would have

completed this thesis without his continuous support. The numerous discussions in

which ideas and opinion were heard and decision taken accordingly were held in a

conducive environment. I owe my gratitude to his family members to bear his absence

while he was busy with the research work. My sincere thanks are also to Dr. P. V. Rao

who despite his busy commitments guided my efforts where ever needed.

I am thankful to the faculty and staff members of IIT, Delhi, especially Prof

S.G. Deshmukh, Prof. A. Kanda and Dr. M. P. Gupta, for their help, encouragement

and feedback.

I wish to place on records my sincere thanks to my university, Aligarh Muslim

University, Aligarh, for sponsoring me to pursue PhD at IIT-Delhi. I would also like to

thank the staffs at Mechanical Engineering Section, A.M.U., for their continuous

encouragement and help whenever needed.

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During the project I greatly appreciated the company of the other Ph.D.

candidates. In particular I would like to mention Bibhushan for his holistic approach to

my problems, Avneet Saxena and Anuj Prakash for their help. Thanks goes to Mr.

Subramanian who despite his hectic schedule did the laborious job of proof reading

the thesis and rending some useful tips and suggestions.

I owe this work to my parents and family members who had a keen desire that

I acquire the highest educational qualification. My mother always prayed for the

successful completion of the thesis. In her I found an ocean of love, encouragement

and patience. I am also grateful to my brothers Mr. Mohd. Khalil, Mr. Shaukat Ali,

Mr. Noor Alam and sisters, for their constant encouragement and supports. My thanks

are also due to Dr. Pervez Alam who always stood by my side whenever I was in

trouble. I am also indebted to my wife Farhat, daughters Maheen and Laveeza who

endure my absence.

Finally I would like to thank all my friends, relatives and family members for

their support and encouragement during this endeavor.

14 (11/CAA tkx-c-4 44/l'

Mohammed Ali

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Abstract

This thesis is aimed at enriching a research theme, focused on exploiting the

planning, design and control strategies in the flexible manufacturing systems towards

achieving make-span performance improvement. A salient contribution of this

research effort is focused on adopting the concept of Flexible System of Integrated

Manufacturing (FSIM) as a central theme related to Flexible Manufacturing System

(FMS) in Computer Integrated Manufacturing System (CIMS) context. Planning

strategies involves system operating under alternative system load conditions namely:

Full Balanced Load (FBL), Balanced Machine Load and Unbalanced Processing Time

(BMLUPT), Unbalanced Machine Load and Balanced Processing Time (UMLBPT)

and Unbalanced Load (UBL). The second planning strategy being considered is

system configurations based on the availability of buffers. The design strategies

include routing flexibility, pallet flexibility and number of pallets in the systems.

Routing flexibility is the capability of processing a part through varying routes. Pallet

flexibility is defined as the ability of the pallets to hold and move efficiently several

part types from one point to other. The influence of these factors on the performance

of FSIM is evaluated. Control strategies manifest itself in the form of dispatching and

sequencing rules.

The main aim of these studies involves suggesting framework, simulation

studies and analyzing the result to highlight important possibilities and implications.

The demo simulation models are for deterministic environment, and the use of discrete

event simulation approach is adopted to offer a focus on dynamic behavior of FSIM

operating under different strategies. The key issues, which are addressed in this thesis,

are: How do different levels of routing flexibility impact the system performance

under the influence of alternative system load conditions? Is the make-span

performance of FSIM significantly superior at different levels of routing flexibility? Is

routing flexibility beneficial with increase in number of pallets in the system? What is

the suitable number of pallets at which maximum benefit is obtained from the system?

Do control strategies play an important role in the performance of FSIM? What is the

impact of control strategies under various levels of flexibility under different

conditions of buffers?

The research shows that for a given system configuration, a given level of

flexibility offers maximum benefit. Increasing flexibility from a given level offers

marginal benefit and can sometime be counterproductive. There is a definite range of

pallets in the system at which the system performs satisfactorily. This range is

dependent on routing flexibility, storage configuration, design and control strategies

etc. It is important to model and determine the right range of pallets that will offer

superior performance for a given set of operating conditions. For a dynamic

environment this may be a very useful knowledge for practitioners. Simulation of the

flexible system modeled shows that storage capacity and configurations has an

important impact on the overall system configuration.

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Table of Contents

Certificate

Acknowledgement ... iii

Abstract

List of Figures xiii

List of Tables xix

List of Abbreviations xxv

1 Introduction

1.1 Background 1

1.2 Motivation ... 2

1.3 Computer Integrated Manufacturing System (CIMS) 3

1.4 Flexible Manufacturing System (FMS) 5

1.4.1 The concept of manufacturing flexibility 6

1.4.2 The emerging needs for manufacturing flexibility 7

1.4.3 Evaluating manufacturing flexibility 9

1.5 Shop floor control in FMS 9

1.5.1 Planning strategies in flexible system 11

1.5.2 Design strategies in flexible system 11

1.5.3 Control strategies in flexible system 12

1.6 An overview of FSIM model 12

1.7 Organization of the thesis 13

2 Literature Review

2.1 Introduction 19

2.2 CIMS 19

2.3 FMS 21

2.4 Shop floor control in FMS 23

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2.4.1 Planning strategies in FMS 24

2.4.1.1 System load conditions 25

2.4.1.2 System configurations 27

2.4.2 Design strategies in FMS 28

2.4.2.1 Flexibility 29

2.4.2.2 Manufacturing flexibility 32

2.4.2.3 Routing flexibility 34

2.4.2.4 Pallet flexibility 36

2.4.2.5 Number of pallets in the system 36

2.4.3 Control strategies 38

2.4.3.1 Dispatching and sequencing rules 38

2.5 Simulation of flexible system 41

2.6 Conclusions 45

3 Research Motivation and Methodology

3.1 Introduction 47

3.2 Research motivation 51

33 Research issues 53

3.4 Research objectives 55

3.5 Research methodology ... 56

3.6 Conclusions 59

4 Development of Conceptual Framework for FSIM

4.1 Introduction 61

4.2 Defining a sample manufacturing systems 66

4.2.1 Key features of sample system 67

4.3 Developments of simulation models 76

4.3.1 Modeling of planning strategies 77

4.3.2 Modeling of design strategies 77

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4.3.2.1 Routing flexibility 78

4.3.2.2 Pallet flexibility 80

4.3.2.3 Number of pallets in the system 81

4.3.3 Modeling of control strategies 82

4.4 Assumptions 84

4.5 Verifications and validation of simulation models 84

4.6 Conclusions 86

5 Performance of FSIM under Alternate Load Conditions

5.1 Introduction 87

5.2 Simulation results and discussions 88

5.2.1 Simulation results under FBL conditions 88

5.2.2 Simulation results under BMLUPT conditions 90

5.2.3 Simulation results under UMLBPT conditions 92

5.2.4 Simulation results under UBL conditions 95

5.3 Simulation results under penalty on increased RF 99

5.4 Conclusions 102

6 Performance of FSIM under Alternative Design and Control Strategies 6.1 Introduction 103

6.2 Simulation results and discussions 104

6.2.1 MST performance under NP at various levels of RF 104

6.2.2 MST performance under RF at given NP with different DR/SR rules 109

6.2.3 MST performance under NP and RF with different combinations of DR/SR rules 112

6.2.4 MST performance comparison under NP, RF and DR/SR Rules 118

ix

6.3 Sensitivity analysis 120

6.3.1 Sensitivity to production volume 120

6.3.2 Sensitivity to part mix 122

6.4 Conclusions 123

7 Impact of Routing and Pallet Flexibility on FSIM 7.1 Introduction 125 7.2 Simulation results and discussions 125

7.2.1 MST performance under PF at various levels of RF 126

7.2.2 MST performance under RF at various levels of PF 135

7.2.3 MST performance under combined impact of RF and PF 141 7.3 Conclusions 144

8 Performance of FSIM with Constrained CB 8.1 Introduction 147 8.2 Simulation results and discussions 148

8.2.1 MST performance under NP at various levels of RF 148

8.2.2 MST performance under RF at given NP with different

DR/SR rules 154

8.2.3 MST performance under NP and RF with different

combinations of DR/SR rules 156

8.2.4 MST performance comparison under NP, RF and DR/SR Rules 161

8.2.5 MST performance under DT for storage and retrieval of

parts from CB 163

8.2.5.1 Impact of DT: Performance of control strategies 164

8.2.5.2 Impact of DT: Performance of routing flexibility............ 165

8.2.53 Impact of DT on MST with increased in NP and levels of RF 168

x

8.3 Conclusions 170

9 Performance of FSIM with Hybrid Buffer System

9.1 Introduction 173

9.2 Simulation and discussions 174

9.2.1 MST performance under NP at various levels of RF 175

9.2.2 MST performance under RF at given NP with different DR/SR rules 180

9.2.3 MST performance under NP and RF with different DR/SR rules 183

9.2.4 MST performance comparison under NP, RF and DR/SR rules 186

9.2.5 MST performance under variable capacity of DIB with constant capacity of CB at given NP 188

9.2.6 MST performance under variable capacity of CB with constant capacity of DIB at given NP 193

9.2.7 MST performance under DT for storage and retrieval of parts from CB 199

9.2.7.1 Impact of DT: Performance of control strategies 200

9.2.7.2 Impact of DT: Performance of routing fleibility 202

9.2.7.3 Impact of DT on MST with increase in NP at different

levels of RF 205

9.3 Conclusions 210

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10 Comparative Studies to Evaluate Performance of Different Configurations of FSIM

10.1 Introduction 213

10.2 Simulation results and discussions 213

10.2.1 MST performance under RF with given DR/SR rules 214

10.2.2 MST performance under NP,RF and DR/SR rules 218

10.2.3 MST performance under NP at different DR/SR rules 224

10.2.4 MST performance under DT at a given level of RF 228

10.2.4.1 Impact of DT on MST at different levels of RF ... 228

10.3 Conclusions 231

11 Conclusions and Scope for Future Work

11.1 Introduction 235

11.2 Conclusions 236

11.3 Contribution of present research work 240

11.4 Managerial and research implications 241

11.5 Limitations of the present work 242

11.6 Scope for future work 243

References 245

Appendix A 257

Appendix B 258

Appendix C 276

Brief Resume 293

Publications 295

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