Assembly specification by gauge with internal mobilities (GIM) - A specification semantics deduced from tolerance synthesis

Currently, standards such as ISO 1101 are used for the geometrical specification of mechanical parts. However, these standards are not sufficient to express exact functional requirements, even for assembly. The objective of this paper is to determine what to express exactly for assembly, that is, create the necessary : specification semantics. A tolerance synthesis model is developed based on variational geometry The model takes into account not only manufacturing deviations and gaps, but also the assembly process and nature of contacts between parts. The specification semantics is deduced from this tolerance synthesis. This semantics is based on virtual gauges, which are composed of an interface with the part and of a structure. The main contribution on the virtual gauge is the concept of internal mobilities allowing displacements between different entities of the gauge. This gauge takes also in account the nature of the contact between parts.