Optimization & Variation Reduction in Quality – Second Edition



Covers how to optimize the average and reduce variation during product design, process design and process improvement.  Provides a unified approach to engineering product and process variation.


ISBN 978-0-9635122-2-2 Hard Cover
By: Dr. Wayne A. Taylor

Book Objective

Provides a unified approach to optimization and variation reduction…
from product concept to manufacturing.

This landmark book integrates statistical process control, design of experiments, robust design methods, Shainan’s methods and other lesser-known practices into a single system for engineering variation and optimizing performance. Professionals engaged in product design, process development, manufacturing and Six Sigma improvement activities will find this common framework has vast practical implications, not least of which is immensely improved communication between the various disciplines in the product lifecycle.
Spotlighting two of today’s most effective techniques – statistical process control and robust design – this landmark book integrates these and other lesser-known practices into a single system. Professionals engaged in product design, process development, manufacturing and Six Sigma improvement activities will find this common framework has vast practical implications, not least of which is immensely improved communication between the various specializations in the product lifecycle.
There are a host of other advantages offered by this comprehensive work, including:

  • An explanation of variation from the engineer’s point of view, addressing variation early in the design process to prevent problems rather than fix them later.
  • An introduction to variation transmission analysis, a key method for driving optimization and variation reduction in the early phases of product design.
  • Emphasis on selecting the appropriate method, with detailed discussions of Multi-Vari charts, analysis of means, component swapping, variation transmission studies, and more.
  • Case studies that illustrate methods from a pragmatic, rather than theoretical, perspective.

By applying the practices and strategies set forth clearly in this book, engineers, scientist, and technical managers will look forward to dramatic improvements in product quality, product cost, and time to market.

Table of Contents

Part I: Principles and Strategies

Chapter 1: The Nature of Optimization and Variation Reduction

1.1 Objective of Book
1.2 Five Categories of Problems
1.3 Three Sources of Variation
1.4 The Goal
1.5 The Importance of Reducing Variation
1.6 Benefits
1.7 Summary

Chapter 2: Three Case Studies

2.1 Hinge Case Study
2.2 Heat Sealer Case Study
2.3 Multi-Head Filler Case Study

Chapter 3: Understanding Variation

3.1 Cause of Variation
3.2 Key Input Variables
3.3 The VIP’s
3.4 Identifying Key Inputs and VIP’s
3.5 Reducing Variation
3.6 Robustness
3.7 Myths About Variation
3.8 Summary

Chapter 4: Strategies for Optimization and Variation Reduction

4.1 Strategies for Reducing Variation
4.2 Strategies for Optimizing the Average
4.3 Objectives During Product Design
4.4 Objectives During Process Development
4.5 Objectives During Manufacturing
4.6 The Complete System
4.7 Summary

Part II: Measurement

Chapter 5: Measuring Variation

5.1 What is Variation?
5.2 Measurement of Statistical Variation
5.3 Histograms
5.4 Variation And Deviations
5.5 Measures of Central Tendency
5.6 Measures of Statistical Variation
5.7 Normal Curve
5.8 Accuracy of Estimates
5.9 Summary
5.A1 Construction of Histograms
5.A2 Calculating Standard Deviations

Chapter 6: Measuring the Three Sources of Variation

6.1 Capability Studies
6.2 Measuring Usage Variation
6.3 Measuring Variation Due to Deterioration
6.4 Summary

Chapter 7: Evaluating Measurement Systems

7.1 Properties of Good Measures
7.2 Measurement Capability Studies
7.3 Measurement Reproducibility Study
7.4 Instrument Bias Study
7.5 Attribute Versus Variable Measures
7.6 Converting Attributes to Variables
7.7 Summary

Part III: Searching for Differences

Chapter 8: Strategies for Identifying Differences

8.1 The General Strategy
8.2 Time Differences
8.3 Product Stream Differences
8.4 Unit Differences
8.5 Within Unit Differences
8.6 Summary

Chapter 9: Control Charts

9.1 Common Cause and Special Cause Variation
9.2 Uses of Control Charts
9.3 Average-Standard Deviation Control Charts
9.4 Special Patterns
9.5 Other Control Charts
9.6 Using Control Charts for Process Improvement
9.7 Using Control Charts for Process Maintenance
9.8 Summary

Chapter 10: Variation Decomposition

10.1 Multi-Vari Charts
10.2 Analysis of Means (ANOM)
10.3 Variance Components Analysis (VarComp)
10.4 Summary

CHAPTER 11: Determining Causes of Differences

11.1 General Approach
11.2 Component Swapping Studies
11.3 Assembly/Setup Studies
11.4 Unit Comparisons
11.5 Conclusion to Part III
11.6 Summary

Part IV: Studying the Inputs’ Effects

Chapter 12: Optimizing the Average

12.1 Studying the Inputs’ Effects
12.2 Identifying Key Input Variables
12.3 Scatter Diagrams
12.4 Screening Experiments
12.5 Understanding the Input/Output Relationship
12.6 Response Surface Studies
12.7 Targeting the Key Input Variables
12.8 Summary

Chapter 13: Variation Transmission Analysis

13.1 Two Approaches to Identifying VIP’s
13.2 Variation of a Polynomial
13.3 Approximating the Variation
13.4 Parameter Design
13.5 Tolerance Design
13.6 Summary

Chapter 14: The Direct Approach

14.1 Measuring Transmitted Variation Directly
14.2 The Noise Array Approach
14.3 Summary

Chapter 15: Conclusion

15.1 Conclusion to Book

What's Changed

Preface Second Edition – 2022

The goal, strategies and methods presented have withstood the test of time and are as valid today as when this book was first written.  But technology has changed.  Gone are all references to calculators.  We now have computers and software to simplify the use of the methods presented.  Since writing this book, I created:

  • VarTran software package to perform variation transmission analysis in Chapter 13.
  • Distribution Analyzer software package to perform capability studies in Chapter 6, including for nonnormal data.
  • Change-Point Analyzer software package for trending as an alternative to control charts in Chapter 9.

There have also been changes in terminology:

  • The capability indices Ppk and Pp have been added.
  • The definition and accuracy and other measurement terms have been adjusted to match the ISO standards.
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