RS method vs Iterative Tolerance Analysis method to optimal tolerance design by using CAT systems

The paper deals with the optimal tolerance design by using CAT systems. It focuses on aspects that characterize the deliverability of assembly functional requirements to tolerance features and design. Starting from previous studies on statistical approaches to tolerance design, two known different methods finalized to optimal tolerance allocation, by using computer experiments with CAT systems, are presented and compared. The first method (named RS) is based on the Response Surface Methodology (RSM). The second one (named ITA) uses an iterative tolerance allocation procedure, starting from a Taylor expression. For both methods the inner characteristics and the adopted approaches are analyzed as well as the final results. Several aspects are taken into account such as the choice of critical factors, the design behaviour under tolerance changes, the amount of preliminary analyses, the time spent and the necessary engineering knowledge. The critical analysis is completed through the discussion of a case study.