Tolerance optimization in assembly stacks based on capable design

Abstract

There is probably no other design effort that can yield greater benefits for less cost than the careful analysis and assignment of tolerances. However, the proper assignment of tolerances is one of the least well understood activities in product engineering. The paper introduces a knowledge-based statistical approach to tolerance allocation, where a systematic analysis for estimating process capability levels at the design stage is used in conjunction with statistical methods for the optimization of tolerances in assembly stacks. The method takes into account failure severity through linkage with failure mode and effects analysis (FMEA) for the setting of realistic capability targets. The application of the method is fully illustrated using a case study from the automotive industry through the use of interactive software.