Automatic generation of 3D assembly feature surface chain groups

associate to dimension based on UG platform

GOU Bo，WU Yu-guang，WANG Guang-lei

（School of Mechanical Engineering，Hangzhou Dianzi University，Hangzhou 310018，China）

Abstract：Aiming at the problems that assembly dimension chain couldn't generate automatically in real sense and rarely considered geometric tolerance in the current，a method for the automatic generation of 3D assembly feature surface chain groups associate to the dimension was proposed based on the theory of tolerance model representing by control points of geometric elements. According to the information requirement of the assembly tolerance modeling，the data structure of a mixed graph stored by computer for assembly tolerance information modeling was established. On the platform of UG NX7.5 OPEN，the assembly information，such as the dimension

and geometry tolerance，geometry structure data，the assembly datum and target information，were removed from the feature model of the assembly and parts. Firstly，the closed loop was determined，and then the 3D assembly feature surface chain associate to the dimension was constructed by searching the assembly tolerance information graph according to the rule of shortest path of establishing assembly dimension chain. Finally，it was broken into 3D assembly feature surface chain groups associate of the dimension one of which just belong to one part of the assembly based on the assembly sequence and design datum. At last，the method was verified by the pin-hole assembly with three orthogonal planar assembly data. The results indicate that dimensions and geometric tolerances are taken into account and a solid foundation is laid for the subsequent tolerance analysis.

Key words：assembly tolerance model；data structure；assembly feature surface chain groups associate to dimension；automatic generation