Modeling of Geometric Variations Within Three-Dimensional Tolerance Zones

A tolerance modeling method of geometric variations within three-dimensional (3D) tolerance domain is proposed.According to the classification method of feature variations and classes of invariance or symmetry in the new generation Geometrical Product Specifications (GPS) system, the proposed method is based on the Small Displacement Torsor (SDT) concept, and SDT is used to represent the geometric deviations between the nominal feature and the fitting feature. Furthermore, the variation zones of several kinds complex or irregular geometric features are constructed, and the corresponding tolerance modeling methods are discussed respectively. Finally, an example is presented to verify the efficiency of the presented method for modeling 3D dimensional and geometrical tolerances.The proposed modeling method based on the complete mathematical foundation conforms with the design philosophy and principle of the new generation GPS standards system.