An Efficient Approach to Interpreting Rigorous Tolerance Semantics for Complicated Tolerance Specification

The significance of tolerance is obvious and undoubted for product design and manufacturing. However, it is not intuitionistic for the computer to understand the tolerance semantics, which heavily baffles the integration of CAD and CAM. In this paper, a uniform approach to interpreting the rigorous tolerance semantics for complicated tolerance specification (CTS) is proposed with the help of reclassification of tolerance based on tolerance zone (TZ). First, the tolerance is reclassified into three categories: Immovable-TZ (ITZ) tolerance, Translational-TZ (TTZ) tolerance and Floatable-TZ (FTZ) tolerance. Second, a uniform method of interpreting the rigorous tolerance semantics is presented based on the variation along degrees of freedom direction (VDOF) for CTSs. To improve the computational efficiency of implementation of interpreting rigorous tolerance semantics, a novel method is proposed to determine the TZ boundary without performing Boolean intersection operations in 3-D CAD systems. Finally, the algorithm is implemented and some test results are given.