Improving product quality and productivity using better guidelines for concept design

The remarkable effectiveness of Japanese practices has led to a growing interest in the US in the development and application of rules and methodologies which attempt to capture design experience. US companies have found unexpected benefits and pitfalls in the application of these rules and methods. In this article, the authors critically examine one of the most widely accepted rules of Design for Manufacturability (DFM): minimize the number of parts. An examination of 240 assemblies and subassemblies has shown that rigid adherence to this rule can lead to unnecessarily complex parts and assembly. Quantitative insights derived from this study have led to a better design goal: minimize and simplify assembly operations. This new rule, which should not be rigidly interpreted, tends to reduce part count, while having the benefit of assuring improved assembly. Another significant advantage of the new design rule is that it results in lower product defect rates as demonstrated by correlations observed for a wide range of products from two different manufacturers. This research links quality to the product concept, enabling a new approach to improving quality at the earliest stages of design