Research On Variation Analysis And Process Optimization Of Autobody Assembly Oriented Manufacturing Precision Control

With the consistent improvement of standard of living in china, the car has become the most important transportation for people in daily life and the demand of auto is growing. At the same time, the consumer are increasingly high demands on the q uality of automotive products. That means, the manufacturer of vehicle should improve the quality and performance of the product. As one of the four vehicle assembly, the assembly quality of car body directly influent the vehicle performance, appearance and sealing. Thus the study of variation analysis and process optimization of auto-body assembly could have great influence on the improvement of product quality.Based on the above reasoning, this article first studied the theoretical basis of Vis VSA assembly variation analysis method and described the process of analysis. The Analytical Target Cascading method and the multiple hierarchy dimension chain of auto-body was applied in the tolerance analysis and optimization of car body. According to the dimension problem, extract the dimension chain based on the structure and process characteristics of body, error an alysis, to verify that whether the tolerance and assembly process meet the requirement of precision. The functional dimension of front suspension mounting points was taken as an example, the welding process was optimized. Variation simulation according different process was conducted by Vis VSA to verify the efficiency of the proposed method.At the same time, the effect of fixture variation on the body assembly variation was studied. Based on variation propagation model of multi-station assembly system, the location robustness was studied. The F-norm of model matrix is proposed as the Positioning robustness index, then the genetic algorithm was used to optimize the locator layout. The method is applied to a car rear floor assembly, the result shows that the method can effectively improve assemble accuracy without increasing other expenses.At last, based on stochastic finite element method, a variation analysis method for the compliant sheet metal welding assembly is presented. The relationship between the assembly variations and fixture locating errors was studied. The result shows that the deviation of measuring point has a positive correlation with the variatio n of the nearby location point. The stochastic finite element method and orthogonal experiment was combined to optimize the fixture locating project. The fixture locating robust design method considering the fixture locating positions as design parameters and the fixture error as noise parameters. A simple sheet metal assembly was used to validate the proposed method.