虚拟装配系统中几何精度三维标注用于实现几何精度在虚拟装配系统中的直观显示及装配尺寸链的交互生成.基于ACIS几何模型得到零件几何精度三维标注所需的精确几何信息和标注点位信息,并根据国家标准和国际规范构建几何精度三维标注模型;在此基础上,进一步建立了几何精度标注相对零件的随动变换和线性尺寸标注的辅助角度尺寸模型.相关模型和算法已在原型系统中得到实现,并通过实例验证了系统的规范性和实用性.
Three-dimensional (3D) GDT provides basic information for tolerance visualization and generation of assembly dimension chains. This paper presents an approach to 3D GDT for mechanical products in virtual assembly system. Points for dimension lines and control frames are derived from ACIS-based geometry, and a 3D GDT model referring to the international standard is developed. In addition, 3D GDT's consequent transformation due to part movement is introduced, and an assistant angular dimension model is built for 3D linear dimensioning. Finally, a prototype system is presented.