Design, optimization and quality concepts all require objective functions for ranking alternatives. From economics and decision theory, a well-developed mathematics of objective functions has emerged. This paper reviews necessary conditions for the existence of an objective function and the consequences of those conditions on concepts such as quality. This approach enables the quick detection and localization of faults based on in-line dimensional measurements of assemblies. The fundamental concepts and industrial implementations are highlighted.
Variation is the root cause of poor quality in product and process.
To reduce the effect of variation the wisdom is not to control the source of variation but to make product and process insensitive to it. The paper demonstrates how managing sensitivity of a design can reduce the effect of variation thus enhance quality in product and process. Changes at any stage can have consequences for every other. We will illustrate this principle with examples from the aerospace industry, and describe some relevant research programs. Designed experiments are used primarily for characterization and optimization of products and processes.