REPRESENTATIONAL PRIMITIVES FOR GEOMETRIC TOLERANCING

The ANSI standard Y14.5 defines a set of geometric tolerances to be used to specify permissible part variations in manufacturing. With the increasing trend towards replacing drawings with solid models, a representation is needed to express these tolerances unambiguously within the context of a solid model. Although the standard is complex, the tolerances can be represented by a small number of tolerancing primitives, providing a few generally applicable concepts. By combining these primitives in different ways, extensions to the standard can be expressed which are consistent with the framework established by the standard. The paper describes these representational primitives and general concepts and how they address the complexities of the standard. This comprehensive tolerance representation, with a few exceptions, allows for the specification of all the standard tolerances. This representation serves as the basis for a computer system for tolerance analysis and synthesis.