Study On Virtual Assembly Of Shafting Parts And Rationality Analysis Of Assembly Structure Based On MDT

Shafting parts are widely used in mechanical products. In the course of designing products, the quality of parts' assemblies is very important. Current CAD software is not enough in the professional design of shafting parts and their assembly, especially in the rationality of shafting assembly structure. In this paper, based on MDT6.0, using MDT VBA as developing tool, the functions of parameterization modeling of shafting parts, virtual assembly of shafting parts and the rationality judgement of assembly structure are realized.Focusing on the Object-Oriented theory and modularization theory, this thesis devided the system into three modules: shafting parts' 3D geometric modeling module, virtual assembly module, assembly rationality analysis and error-modified module. Through abstracting the structure of shafting parts, the system defines basic graphic units and realizes the characteristic modeling of shafting parts through Boolean operations on graph units. Based on Object-Oriented technique, shafting parts are divided into several kinds of classes, such as shaft segment class, standardized-part class etc. Because of the encapsulation and succession characters of class, the above method is of advantage to the pick-up of information. Parameterization design of shafting parts is realized by the interaction between human and computer.In the study of the virtual assembly module, the parts' orientations are determined by defining assembly constraints, such as insert, mate etc. And the foundation of assembly modeling database give facilities for the information's pick-up in the rationality analysis.The concept of "knowledge" is introduced into the assembly rationality analysis module. Based on the summarization of shafting structure's familiar mistakes, a knowledge database is established using the describing method of Post. Through setting rules in the knowledge database, the rationality analysis of shafting structure can be completed. If there are mistakes in the shafting assembly structure, the design of shafting parts and assembly constraints can be modified to make the whole design right.