Automated tolerance analysis for mechanical assemblies modeled with geometric features and relational data structure

Abstract

The automation of tolerance analysis of assemblies is based on the development of the data structure for their representation in geometric modeling, and the computerization of procedures developed by Bjorke. The data structure contains assembly-level and component-level relationships to automate the generation of the tolerance chain for a user-selected sum dimension. A statistical analysis is performed on a sum dimension, the characteristics of which can be easily generated by the hierarchical relationships and the mating conditions between components contained within the assemblies' geometric data structure. The method uses a truncated unit beta distribution for the sum dimension and the contributions to the sum dimension by the statistical properties of 15 link types. The user supplies the tolerance range of the sum dimension and its location within the distribution. The program provides the user with a graphical display of the sum-dimension distribution, the specified range and location of the tolerance, and the results of the numerical integration of the distribution that generates the confidence limits for a given application.