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Engineering Robust Designs with Six Sigma

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Engineering Robust Designs with Six Sigma


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Apply Six Sigma for developing high quality, low-cost product innovation that distinguishes your product from the competition.

° Shows how to apply Six Sigma process, methodologies, and tools to develop robust engineering products, processes, and services.

° Examples and case studies illustrate the practical applications of the robust design principles and Six Sigma Methodologies.

° A guide to developing industrial experiments to improve product quality.


  • Copyright 2005
  • Edition: 1st
  • Book
  • ISBN-10: 0-13-144855-2
  • ISBN-13: 978-0-13-144855-1

"Dr. Wang's work is of the highest caliber. He has the ability to take very complex subjects and to present them very clearly. He makes excellent use of examples throughout the book."
--Donald W. Sova, Ph.D., Booz Allen Hamilton

"I have not seen a text that provides such broad coverage of the topic. The foremost feature of this is competitive advantage. This product should provide superior utility at a lower cost to both the consumer and to the producer. Competitive advantage is rapidly becoming a necessity to stay in the game."
--Jeffrey B. Lynch, Northrop Grumman Corporation

"Few, if any, other people have the experience in both quality engineering (Six Sigma) and in product engineering that could match Dr. Wang's. A great deal of the unique value of this book is the integration of ideas from these two disciplines."
--Marvin L. Roush, Professor Emeritus, University of Maryland at College Park

Leverage Six Sigma to Transform Product Design and Development

Today's customers demand unprecedented reliability, efficiency, flexibility, and affordability. To deliver products, this robust, quality manufacturing isn't enough; Six Sigma processes must begin in the earliest stages of design. Now, one of the field's leading experts offers the first complete blueprint for implementing Six Sigma product design. John X. Wang has transformed product design at companies ranging from Maytag and Visteon to General Electric. In this book, he illuminates the full spectrum of proven techniques, from Voice-of-Customer (VOC) and Critical-to-Quality (CTQ) to Kano modeling. You'll discover how Six Sigma can bridge critical gaps between research and development, product and process, and how it can help you quickly respond to any change, from new suppliers to emerging customer requirements. Topics covered include

  • Starting out: identifying projects, organizing teams, developing VOC models,
  • formulating CTQ characteristics
  • Creating robust design concepts: principles, practical techniques, and engineering parameters
  • Kano modeling: delighting customers and responding to their evolving requirements
  • QFD: building a "house of quality" that reflects both spoken and unspoken customer needs
  • Failure Mode and Effect Analysis (FMEA): preventing failures, mitigating risks
  • Minimizing lifecycle cost through effective tolerance design
  • Designing in long-term reliability

If you're an engineer, manager, or quality professional who's ready to drive breakthrough improvements in product design and development, Dr. John X. Wang will guide you, every step of the way, to success.

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Achieving Robust Designs with Six Sigma: Dependable, Reliable, and Affordable

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Table of Contents

Preface xiii
About the Author xvii

Chapter 1. Achieving Robust Designs with Six Sigma: Dependable, Reliable, and Affordable 1

1.1 Six Sigma and Robust Design 1
1.2 Identify Project and Organize Team 3
1.3 Develop VOC Models 4
1.4 Formulate Critical-to-Quality Characteristics 6
1.5 Control Energy Transformation for Each CTQ Characteristic 8
1.6 Determine Control and Noise Factors 12
1.7 Assign Control Factors to the Inner Array 15
1.8 Summary and Road Map 20
Bibliography 23

Chapter 2. The Kano Model: Listening to the Voice-of-Customers 25

2.1 How to Make the Customer Happy 26
2.2 Customer Requirements Over Time 32
2.3 Control Factor Levels: Ensure Three Types of Quality 34
2.4 Noise-by-Control Analysis: Making Products More Robust 38
2.5 Variability Reduction 40
2.6 The Outer Array: An Orthogonal Array Specifying Multiple Noises 43
2.7 Selecting Noise Levels 45
2.8 Summary 47
Bibliography 48

Chapter 3. Quality Function Deployment: Building a House of Quality 51

3.1 Market Research and Determining Customers' Needs 52
3.2 Goal Tree: Spelling Out Unspoken Needs 55
3.3 Building a House of Quality 58
3.4 Deploy Quality Through Design of Experiments 63
3.5 Experiments for Deploying Robust Quality Functions 68
3.6 Summary 73
Bibliography 74

Chapter 4. Theory of Inventive Problem Solving: Creating Robust Design Concepts 77

4.1 Contradiction: The Gateway to New Designs 79
4.2 Thirty-Nine Engineering Parameters to Standardize CTQs 80
4.3 Forty Principles to Identify Design Solutions 84
4.4 Calculating the Average of Control Factor Effects 93
4.5 Calculating the Effects of Noise Factors 96
4.6 Noise-by-Control Interaction Effects 99
4.7 Summary 102
Appendix 103
Bibliography 111

Chapter 5. Failure Mode and Effect Analysis: Being Robust to Risk 113

5.1 The Historical Context of FMEA 114
5.2 Using FMEA to Prevent Failure Before Any Harm Is Done 117
5.3 Identifying Functions and Failure Modes 118
5.4 Identifying Effects and Severity 123
5.5 Understanding Causes 127
5.6 Assessing Current Controls 129
5.7 Using FMEA for Risk Management 131
5.8 Summary 134
Bibliography 135

Chapter 6. The P-Diagram: Laying Out a Robust Design Strategy 139

6.1 Experimental Design and the P-Diagram 139
6.2 Quality Loss Function 147
6.3 Noise Factor Management Strategies 150
6.4 Three Phases: From Thought to Things 156
6.5 Summary 159
Bibliography 160

Chapter 7. Parameter Design: Optimizing Control Factor Levels 163

7.1 Identify Project and Team 166
7.2 Formulate Ideal Function 168
7.3 Formulate Dynamic Parameter Design 171
7.4 Assign Control Factors to an Inner Array 174
7.5 Assign Noise Factors and Signal to an Outer Array 178
7.6 Conduct the Experiment and Collect Data 183
7.7 Analyze the Data and Select an Optimal Design 186
7.8 Summary 192
Bibliography 193

Chapter 8. Tolerance Design: Minimizing Life-Cycle Cost 195

8.1 Tolerance Design versus Tolerancing 197
8.2 Reduction in Variability 201
8.3 Tightening Tolerance Selectively to Maximize Quality-versus-Cost Tradeoffs 203
8.4 Quantifying the Quality Loss Function 204
8.5 A Wheatstone Bridge System 210
8.6 Summary 213
Bibliography 216

Chapter 9. Reliability Design: Giving Customers Long-Lasting Satisfaction 219

9.1 Reliability and Six Sigma 220
9.2 Reliability and Stress-Strength Interference 231
9.3 Stress-Strength Interference Sigma Calculations 241
9.4 Summary 248
Bibliography 248

Appendix. The Process Map: Engineering Robust Products with Six Sigma 251

Index 255


Untitled Document

This book is written for engineers, who have a dramatic impact on our world. The essence of the engineers' job is engineering robust products for the benefit of people. Robust product is not just strong. It is also efficient, flexible, mistake-proof, and affordable. The term engineering robust products encompasses design and process flexibility that rapidly and affordably accommodates changing customer requirements. As an engineer and an engineering manager, I have worked for the power utility, aerospace, transportation, automotive, and appliance industries. I have the privilege to witness the strong needs and challenges for developing dependable power supplies, reliable manned flight vehicles, low-emission transportation systems, high efficiency cars, and cost-competitive appliances. Engineers consider many factors when developing a new product. For example, in developing a hybrid car, engineers determine precisely what function the car needs to perform; design and test the car's components; fit the components together in an integrated plan; and evaluate the design's overall effectiveness, cost, reliability, serviceability, and safety. This process applies to many different products, such as Magnetic resonance imaging (MRI), internets, gas turbines, helicopters, and even toy gyrocopters for kids. Within the next decade, emerging technologies will make possible novel applications that integrate computation into the design, manufacturing, and application environments: smart materials, self-reconfiguring robots, self-assembling nanostructures. We are faced with the challenge of achieving coherent and robust behavior from the interactions of multitudes of elements and their interactions with the design, manufacturing, and application. These new environments highlight the limits of our current engineering and techniques, which still largely depend on precision parts and controlled environments to make product dependable and reliable.

The goal of engineering robust products is to deliver customer expectations at affordable cost regardless of customer usage, degradation over product life and variation in manufacturing, suppliers, distribution, delivery, installation and service. Dr. Taguchi's robust design allows experiments to be performed and prototypes to be tested on multiple factors at once so that the product becomes insensitive to usage conditions and other uncontrollable factors. Since randomness and scatter is a part of reality everywhere, Six Sigma design techniques are necessary to design quality into products. Six-sigma quality describes a product development and manufacturing process of highly robust quality. Achieving six-sigma quality ensures both dependable product quality and production efficiency. The book title Engineering Robust Products with Six Sigma denotes the use of a disciplined Six Sigma process in conjunction with a robust product design. The appropriate application of robust engineering principles with Six Sigma process will enable product development programs to quickly deliver high-quality, low-cost products that fully meet the customer's needs. Product value attracts customers, quality brings in respect, and innovation distinguishes your product from the competition. Engineering robust products with Six Sigma bridges the gap between Research & Development, invention and innovation, and product/process development. It enables engineers to develop products and processes which perform consistently as intended under a wide range of user's conditions throughout their life cycle. It also allows engineers to develop or change product formulas and process settings to achieve desired performance at the lowest cost and in the shortest time. A few reviewers of the book work for the National Aeronautics and Space Administration (NASA). This reminded me of the fact: "All the Astronauts who landed on the Moon were engineers " and we are following their footprints to engineering robust products for the humankind.

-- John X. Wang


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