Study On Generation Of Assembly Dimension Chain And Its Realization Based On 3D CAD System

Binding projects supported by National Nature Science Foundation of China (50275136) and Natural Science Foundation of Zhejiang (502016), the research on generation method of assembly dimension chain and its realization based on 3D CAD system is carried out. A prototype system based on the SolidWorks is developed to validate the method.In chapter 1, the development and the recent status of the CAT research are presented. Based on the analysis of the key technologies, the research content and the thesis structure are given.In chapter 2, tolerance semantics defined by ISO/TC 213 is analyzed. The geometrical feature definition of the GPS (Geometrical Product Specifications) and verification operation is introduced. The characteristics of the feature are studied.In chapter 3, the feature classification of TTRS (Technologically and Topologically Related Surface) and the constraint method of SolidWorks are analyzed. Based on the VGC(Variational Geometric Constraints) theory, a rule to set up the loop circuit for assembly dimension chain is put forward. The generation method of VGC network for assembly dimension chain is presented.In chapter 4, the information of the assembly dimension chain is expressed by means of database. The database structure is given. A database for assembly dimension chain is set up.In chapter 5, generation principle of the assembly dimension chain is presented faced to 3D CAD drawing. The dimension and assembly information is acquired from the 3D assembly drawing after the closing loop is specified by user. Based on the VGC network, the shortest path in the network is searched. The tolerance chain is generated from the database.In chapter 6, the character of design tool(SolidWorks API), platform(SolidWorks) and programming language(Visual Basic) are introduced. A generation prototype system of assembly dimension chain is developed. A sample is given to prove the effectiveness of the system.In chapter 7, all of the research work is summarized, and the future research work is presented.