Representation of Tolerances in Solid Modelling: Issues and Alternative Approaches

The lack of facilities for representing tolerances and related information is a major deficiency of contemporary solid modellers. This paper discusses the semantics of tolerancing for mechanical parts, with particular emphasis on the problems that arise when the features of physical objects cannot be assumed to have perfect form (e.g., when a machined hole is not perfectly cylindrical). Alternative theoretical approaches are proposed, and the representational implications of each approach are explored