CAD-based integrated tolerancing system

Assembly tolerance analysis involves the determination of tolerances of critical dimensions. This paper addresses two basic areas in tolerance analysis and allocation. (1) Dimension normalization, which identifies the relevant functional dimensions. A new algorithm called the dimension block diagram (DBD) algorithm for dimension normalization is presented. (2) Dimension representation, which provides a robust framework for representing the tolerance chain. A new dimension representation framework using Assembly Dimensional Tolerance (ADT) tree is presented. The two methodologies are automated and integrated within the framework of a CAD system using an Expert System. A computer test bed software has been developed demonstrating the viability of this approach.