Expanding Tolerance Analysis for a Robust Product Design

A robust product design can be characterized in many ways, but perhaps the most direct definition is the design that maximizes the profitability for the company while consistently meeting all of the expectations of the customer. For the mechanical specifications of the design “robust” typically means using the least expensive manufacturing processes available, processes that are most often associated with introducing the most part-to-part variation. The challenge for the successful engineer is thus to define part and assembly specifications which result in a quality product, as perceived by the customer, despite using manufacturing processes that may be considered to have less quality than their more expensive alternatives. While the objective of achieving a robust product design is rather straightforward, the actual detailed process for achieving it is more complicated. It involves a combination of skills including assembly engineering, statistics, an understanding of various manufacturing process and their associated costs, and a language for communicating the requirements to others that is seldom taught in engineering curriculums. It therefore comes as no surprise that different engineers with similar competency levels and background experience will still often arrive at significantly different design specifications when faced with a common set of objectives. Fortunately software tools are that can help standardize the process and hence drive different engineers towards more similar solutions are available. This paper reviews the primary steps needed to achieve a robust design using advanced software that combines the multiple disciplines required with a methodical, repeatable process. Case studies of companies who have implemented these steps are presented with discussion of the lessons learned from these implementations. This paper (or a similar version) was presented in 2014 at the 13th CIRP Conference on Computer Aided Tolerancing in Hangezhou China and NAFEMS in Colorado Spring, CO. © 2014 Chris Wilkes, Sigmetrix LLC.