三维CAD系统中变动孔特征通用生成方法

公差给出了有误差的真实加工零件可以变动的极限范围，然而现有的三维CAD系统无法有效地表示、生成出零件带公差信息的变动体。以孔特征为研究对象，系统地研究了其所有可能的公差要求组合，讨论了孔特征中心轴线可变动范围的快速确定方法。结合给定的不同公差类型，讨论了孔轴线和孔表面变动体生成方法。建立了孔特征变动体生成的数学模型，并给出了实现算法。最后给出了变动孔特征的实现实例。

GENERIC APPROACH TO GENERATING VARIATIONAL GEOMETRY OF HOLES IN THREE DEMENSIONAL CAD SYSTEMS

Tolerance is used to give the variational extremum for the real parts and the information can now be added to the parts as text attributes in three demesional CAD systems. But how to interpret the information and generate the variational geometry for the parts is still a difficult task. How to generate the variational geometry for the holes is systematically analyzed. At first all possible combinations of tolerance specifications for holes are given. An efficient method for determining the variational boundary for the hole axis is proposed based on the given tolerance requirement. A mathematical model for the generation of variational geometry of the holes is systematically deduced and the realization approach is developed based on the geometric modeling kernel-ACIS. An example is given to illustrate the proposed model.