INTEGRATED CAD FRAMEWORKS - TOLERANCE REPRESENTATION SCHEME IN A SOLID MODEL

The major objective of this paper is to develop a representational sch eme for geometric tolerances that are to be interfaced with a solid mo del. This includes the development of (i) an efficient user interface system for input of tolerance information, (ii) a suitable tolerancing data module (to be attached to the solid model), and (iii) an informa tion retrieval system from the stored database for future tolerance an alysis. This user interactive environment which enables the user to in put the tolerance information in both the unevaluated (CSG) and the ev aluated (B-Rep) databases, requires an effective linking mechanism bet ween the CSG and the B-Rep data models at each stage of the object dev elopment. This has been achieved through the development of a referenc e face list. Tolerance information has been attached with this face li st as ''constraint nodes,'' which are formed and updated after each '' set operation.'' Several functions have also been developed to retriev e essential information from the data structure in order to answer var ious queries. The prototype system has been implemented on a polyhedra l solid modeler based on this representational scheme.