The prediction and management of the variability of manufacturing operations

Aim: To investigate methods that can be used to predict and manage the effects of manufacturing variability on product quality during the design process. Methodology: The preliminary investigation is a review and analysis of probabilistic methods and quality metrics. Based on this analysis, convenient robustification methods are developed. In addition, the nature of the flow of variability in a system is considered. This is then used to ascertain the information needed for an input variable when predicting the quality of a proposed design. The second, and major, part of the investigation is a case-by-case analysis of a collection of manufacturing operations and material properties. Each is initially analysed from first principles. On completion, the fundamental causes of variability of the key characteristic(s) are identified. Where possible, the expected variability for each of those characteristics has been determined. Where this determination was not possible, qualitative conclusions about the variability are made instead. In each case, findings on the prediction and management of manufacturing variability are made.