Welding Deviation Analysis And Tolerance Optimization Of Body Front Floor

In order to improve the level of automobile body manufacturing,the company has been committed to researching how to reduce the assembly deviation of thin-plate parts so as to improve the welding and assembly accuracy of thin-plate parts.Based on the “virtual matching of body-in-white flexible parts” project of an automobile inspection tool manufacturer,this dissertation uses the front floor assembly of a certain vehicle model in the project as a carrier to study the welding deviation analysis and tolerance optimization of flexible sheet parts.The main research work and results of this dissertation are as follows:(1)This dissertation discusses the sources and factors of welding deviation of flexible sheet metal,mainly including stamping quality,welding fixture positioning,welding deformation and welding structure design.It has a guiding role for positioning point optimization design,welding assembly deviation analysis and tolerance optimization of sheet metal.(2)The coordinates of the positioning points of the thin plate parts that make up the front floor are used as the design variables,and the average value of the deviation of the measuring points when the thin plate parts are in the clamping state is used as the response value.The BBD method is used to design the test plan and the finite element software is used for simulation Analyze to obtain the response value of the test plan;The response surface method(RSM)was used to establish a mathematical model of the positioning point coordinates and the mean value of the deviation of the measurement point in the clamping state of the thin plate,and the method of variance analysis was used to test the significance and adaptability of the mathematical model;Finally,the response surface method is used to optimize the location of the positioning point,and the optimization results of the model prediction are tested.The results show that the model fits the simulation test more truly.(3)Based on the theory of the influence of fixture positioning deviation on the assembly deviation of sheet metal parts in the welding process,according to the welding assembly process and the actual measurement deviation data of the positioning block of the welding fixture,the simulation model of the welding assembly deviation analysis of the front floor is established,and the finite element simulation analysis of the welding process of the front floor central passage,the left lower floor and the right lower floor is completed,The welding assembly deviation of the front floor assembly is obtained,which provides data for further tolerance optimization of flexible sheet metal welding.(4)Use 3DCS tolerance simulation analysis software to analyze the sensitivity analysis and contribution of the deviation source of the front floor assembly.On this basis,taking the minimum manufacturing cost and quality loss cost as the optimization objective,and the processing capacity limitation and assembly function requirements as the constraints,a multi-objective tolerance optimization mathematical model is established.The improved particle swarm optimization algorithm with decreasing weight coefficient is used to solve the tolerance optimization on MATLAB.The results show that the optimization objective can quickly converge to the optimal value,and the optimized tolerance can meet the requirements of assembly function while saving the manufacturing cost and quality loss cost.