Research On Case-Based Design For Biw Framming Flexible Fixture

The car body is assembled and welded by 70~90 sets of welding fixtures with about 400 press parts, and among them the fixture for assembly body in white is the key on the assembly precise of the body and production capability. With the unceasing accelerated renovate and upgrade speed of the car type and the cost down of the development, the assembly body in white fixture faces the challenge of the new technology such as flexibility, modularize as well as reconfiguration. Presently the development of the assembly body in white fixture in our country depends on the foreign supplier above 90%, it has been the important problems for the long period development and big investment during improving our own development capability of the car product. It is great significant to carry out the research of flexible fixture design technology of assembly body in white.Combining with study trend at home and abroad, this paper carried out the study on the position of fixtures, the features of the flexible parts assembly and case based design theory. By comprehensive analysis of technical features of schematic design for assembly body in white on every car type in Shanghai VW Automotive, the design and optimization method of flexible fixture for assembly body in white came into being, on this basis, making the design and optimization for one new car model called Model-Y in SVW, and it was applied in the actual production.Firstly the study and summary on basic theory of car body manufacture and welding fixture structure design was carried out, including typical positioning and clamp component design, N-2-1 positioning principle and optimization of position point based on minimal deformation. The main welding and assembly features of the body parts were brought forward through cases analysis: geometry features, location features and assembly features. It is indicated that the geometry and assembly features determined the type and structure of the welding fixtures. On this basis, the case based schematic design method, flow and index, search reuse mechanism of body welding fixtures were constructed.Guided by case based design theory, starting from technical analysis of requirement from the fixture design for assembly body in white, the technical requirement features of Reference Point System(RPS) and Functional Dimension System(FDS) for the fixtures of assembly body in white were studied, and schematic design cases of assembly body in white fixtures for various car models of Passat, Polo, Touran and Octavia were fully analyzed and compared, it has established a basis in developing case based fixture design of assembly body in white of for new follow-up car models.Finally, the study results of theory and project practice were summarized, and also were applied in new car model of Model-Y in SVW. During the practice, it was started from the features of assembly body in white of this car model, and compared with corresponding cases; the optimized system design for basic clamps unit of assembly body in white fixtures, layout optimization and reconfiguration design for the fixtures were carried out and successfully applied in actual research and manufacture, thee cost of development was reduced exceeding 50%, and remarkable economic results have been achieved.The research work of the thesis has accumulated good experience for the design and manufacture of the car body flexible welding fixture in SVW, and provided the useful engineering reference for the design technology developing of the car body flexible welding fixture in our country.