The Applied Research Of Local Tolerance Technology Based On ZW3D Platform

At present,due to the tolerance value caused by the calculation of instability,geometric representation of the problem is accurate in the 3D modeling normally.Such as different CAD platform use to do data exchange will cause quality problem,the tolerance model in the new CAD platform editing gets error or fail directly.In this paper,the problem of geometric tolerance is analyzed and studied.Based on ZW3 D,a local tolerance technique is used to solve the problem of geometric tolerance and improve the stability and robustness of the whole modeling system.Firstly,the paper studies the constitutive relations of geometric topologies in the B-Rep model,the principle of geometric tolerance and the causes of the analysis.3D modeling problems caused by geometric tolerance are analyzed,including data import,Boolean Operation,drafting projection,the causes of these three types of problems through the geometric figures and application cases for specific analysis.Then,a tolerance technique of local tolerance method is proposed,which optimizes the judgment range and calculation rules of the tolerant vertex and edges in ZW3 D.Finally,the local tolerance technique is used to solve the modeling problem caused by the three kinds of geometric tolerances in ZW3 D.Which includes the following points.For the data interaction problem caused by geometric tolerance,a new import strategy based on tolerant modeling is implemented in ZW3 D,and the related algorithms of geometric topology mapping and recognition in the import process are optimized.For the failure problem of the Boolean operation caused by the geometric tolerances,a method to handle the intersection line through the tolerant edge or vertex is proposed and implemented,improve the algorithm to ensure the intersection can be closed loop and improve the stability of the Boolean operation.For the projection error of drafting caused by the geometric tolerances,a method of constructing auxiliary geometry is proposed and implemented to judge whether the ray method passes the tolerant edge or the tolerant vertex.improve the accuracy of drafting.