Computer-aided tolerance specification of preliminary designs based on variation analysis

Abstract

A proper tolerance specification ensures assemblability as well as functionality of products and considers associated manufacturing costs. Therefore, numerous, mostly rule-based computer-aided approaches aim to support this challenging task. However, the aspect of functional performance is often considered only indirectly or generically, e.g. without taking into account existing dimension relations, so that iterative manual adjustments are necessary. In order to overcome this shortcoming, a new method is presented, which automatically generates specific tolerance specification proposals on the basis of degree-of-freedom analyses of the contact faces contributing to a defined assembly function. Thus, it enables a reliable, function-oriented tolerance specification of preliminary designs already in early product development stages. The novel approach is prototypically integrated into a CAD system and demonstrated by means of a crank drive mechanism.