Managing Quality

Chapter 17. Design of Experiments

I. Ferguson and B. G. Dale

Introduction

The design of experiments is a series of techniques which involve the identification and control of parameters which have a potential impact on the performance and reliability of a product design and/or the output of a process, with the objective of optimizing product design, process design and process operation, and limiting the influence of noise factors. The methodology is used when we need to analyse the significance of effects on system outputs of different values of design parameters. The objective is to optimize the values of these design parameters to make the performance of the system immune to variation. The concept can be applied to the design of new products and processes or to the redesign of existing ones, in order to:

• Optimize product design, process design and process operation

• Achieve minimum variation of best system performance

• Achieve reproducibility of best system performance in manufacture and use

• Improve the productivity of design engineering activity

• Evaluate the statistical significance of the effect of any controlling factor on the outputs

• Reduce costs

Design of experiment techniques, in particular for process improvement, involves the identification and control of those parameters or variables (termed factors) which have a potential influence on the output of a process, choosing two or more values (termed levels) of these variables and running the process at these levels. Each combination ...