These concepts are developed to obtain a small set of

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Unformatted text preview: to write and read specifications. For tolerance analysis or synthesis, the skin model is reduced to a predictive model, taking into account parametric variations (angles and distances) and sometimes form variation of the workpiece. For coordinate metrology, the skin model is reduced to the points measured on the workpiece. Geometric features We distinguish different types of elements: ideal features, non-ideal features and limited features. We name ideal features, features such as : • a plane of the nominal model of the part, • a cylinder fitted to a real feature nominally cylindrical. 40 L. Mathieu and A. Ballu We name non-ideal features, features such as: • a surface portion of the model of the real surface of a part, • a real axis. Operations The operations used to define the specifications can be divided into six classes, partition, extraction, filtration, collection, association and construction. A partition is an operation used to identify bounded feature(s) from non-ideal feature(s) or from ideal feature(s) A filtration is an operation used to create a non-ideal feature by reducing the leve...
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