Dimensioning and functional tolerancing aided by computer in CAD/CAM systems

This communication presents works of research achieved at the DIAM/IUSPIM on the dimensioning and functional tolerancing of the complex mechanical systems aided by computer in CAD/CAM systems. The dimensioning and functional tolerancing processing has been formalized in using the principle of the envelope. It integrates clearance and contact evolution of mechanical systems in functioning. It integrates production constraints associated by designer to each mechanical part. It allows one to research and manage manufacturing dimension chain conflicts and distribute tolerances. The intervention of the user in the processing insures the tolerancing adaptation to each particular mechanical system. An autonomous computer tool called “CotAO” was made to achieve dimensioning and functional tolerancing processing. The efficiency and the attractiveness of the processing will be obtained by “CotAO” interfacing with a CAD system. This interfacing necessitates, often, the achieving of an adaptation module of the host CAD system. The present “CotAO” interfacing is being made with the Autocad software. The use of such tools contributes to the tolerancing optimization and to the improvement of the mechanical part definition quality. It should appreciably shorten the time necessary to define manufacturing dimensions. It would lead to evolution in the design-manufacturing cycle to a better CAD/CAM system integration