The mathematical model has to express the real world

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Unformatted text preview: et al., 1993]. There are two main aproaches for tolerance analysis: parametric and geometric analysis. Parametric analysis (similar to vectorial) views each object as a set of scalar parameters. In a dimension-driven variational geometry system, the parameters are linear and angular parameters. Tolerances are viewed as limits on the parameters values [Chase, 1999]. Parametric tolerancing is based on a different concept than the geometric tolerance and is not supported by standards. A conversion process is needed to derive parametric tolerances introducing uncertainties. The final result of the analysis depends on the parameters chosen [Serre et al., 2003]. The advantages of parametric analysis are that algorithms tend to be relatively simple and the geometry involved is only a perfect geometry. 38 L. Mathieu and A. Ballu Geometric analysis define constraints between faces expressing the fact that a geometric element must lie in a zone. This approach is the most important solution adopted by researchers [Ballot et al., 1997], [Giordano et al., 1993], [Desrochers et al., 2003] and CAT developers: Valysis from Tecnomatix, VSA-3D from VSA Inc. Geometric tolerancing tends to be in conformance with...
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