Development of a function oriented computer aided tolerancing (FOCAT) system

Abstract

Functional tolerancing of a mechanical part depends on the assembly and manufacturing function. This paper presents an approach for functional tolerance design and optimization. Functional surfaces are classified according to ISO specification. Dimensional and geometric tolerance types are specified based on design rules. Well-constrained analysis is presented to avoid over- and under- constrained tolerance design. A tolerance values optimization model is established with manufacturing cost functions and assembly stackup constraints. A computer-aided tolerancing (CAT) system is developed to provide designer with an effective tool for ensuring the functional tolerancing of the entire assembly. The system is applied to perform a tolerance design for a three-dimensional (3D) assembly .