Tolerance Analysis And Optimization About The Body Welding Of Special Vehicles

With the development of modern manufacturing industry,manufacturing enterprises have more and more requirements for welding precision.The welding accuracy is influenced by many aspects,and the tolerance design has great influence on the precision of welding.Traditional tolerance design mainly relies on the experience of predecessors to design.The Parts are usually treated as rigid bodies for analysis.Because the flexible parts of the body sheet have the characteristics of easy deformation,especially the welding deformation during the welding process of sheet metal parts,which causes the traditional tolerance design difficult to meet the body and other flexible parts of tolerance optimization allocation requirements.Therefore,this paper takes a special vehicle body wheel cabin welding technology as an example,considering the influence factors of welding deformation,the distribution optimization of assembly tolerance is carried out.Firstly,this paper analyzes the factors influencing the deviation of vehicle body welding,aiming at the problem of easy deformation in the process of body plate welding,and the simulation and calculation analysis of the welding body with FEM software.The results show that the welding deformation has great influence on the welding quality,which is not negligible in the optimization of tolerance distribution,and a variety of simulation analysis is carried out on the welding sequence influencing the factors of welding deformation.By comparing and analyzing the influence of each welding sequence formulation plan on the deformation quantity,the welding sequence formulation scheme suitable for the body sheet parts is obtained.Then,the mathematic model of tolerance distribution optimization is researched in this paper.Aiming at the contradiction between quality and cost,this paper establishes a mathematical model of tolerance allocation based on the objective function of minimizing the cost of manufacturing cost and quality loss,which is constrained by the tolerance constraint and processing capability of the welding dimension chain,and optimizes the optimization calculation by using particle swarm optimization with good stability and fast speed.Finally,in view of the problem of low welding precision in the process of a special vehicle,the tolerance distribution is optimized by considering the factors of welding deformation.According to the influence factors of welding deformation in welding process,the welding sequence of the wheel cabin is established by using the best welding sequence scheme,so as to achieve the minimum deformation quantity.Combined with the result of welding deformation simulation,the welding deformation factor is added to the assembly tolerance constraint condition,and the tolerance allocation is optimized for the body wheel cabin.And the tolerance distribution optimization result is analyzed and evaluated by the deviation analysis software VisVSA,the results show that the optimized assembly quality is improved obviously,and the total loss cost is guaranteed.This paper verifies the rationality of tolerance distribution by using the tolerance allocation optimization method during the welding process of thin plate flexible parts.