| Forming process planning is the most important and basic work in modern manufacturing industry,which is the bridge of product design and manufacturing.At present,the production process planning is often unreasonable,which leads to long processing time,poor product quality and low production efficiency.Therefore,it is of great significance for improving product quality to plan the forming process of complex box and study its forming limit.In this paper,reverse modeling method and feature reduction method are used to make a reasonable planning for the forming process of complex box parts.Dynaform finite element numerical simulation combined with experimental method is used to optimize the forming process and forming defects of complex box parts.The main research work and corresponding conclusions are as follows:1)Based on the analysis of the structure and forming characteristics of complex box shaped parts,four forming process schemes are put forward: scheme I “blanking /shearing + two-step drawing + cutting head and cutting tail”;scheme II “blanking /shearing + one-step drawing + cutting head and cutting tail”;scheme III “blanking /shearing + one-step drawing + cutting head + flanging”;scheme IV “blanking / shearing+ one-step drawing + punching and cutting edge + flanging and flanging”.Through the feasibility analysis and Simulation Research of these four process schemes,the best forming process scheme is obtained: “blanking / shearing + one-step drawing +punching and trimming + flanging”.2)The blank model is established,the calculation formula of the blank size is derived,and the approximate shape and size of the blank are obtained.According to the first process model developed by the finite element software Mstep inverse algorithm,the initial contour size of the elliptical billet is 148.36×80.85 mm,and the optimal shape size of the billet is 150×86 mm after modification.3)The optimum technological parameters are obtained: the ultimate thickness of blank is 0.6 mm,the effective blank holder force is 20 k N,and the speed is 2000 mm / s.The hole size is 24.86×24.16 mm,and the hole fillet radius is 3.5 mm;the cutting line size is 126×39 mm,the cutting line fillet radius is 10.5 mm,the draft angle of the hole turning concave die is 7 °,the draft angle of the punch is 7.2 °,and the punch fillet radius is 10 Mm,the complex box-shaped parts with the same flanging height,less concave convex band at the mouth,smooth edge and no burr are obtained,and the experimental results show that the parameters are reasonable.4)By optimizing die structure and blank shape,improving material plasticity,reducing friction coefficient,setting block blank holder and drawing rib,the problems of workpiece surface wrinkling,fracture and hole turning deformation are solved.The results show that:(1)the smaller the fillet radius or the larger the blank holder force,the lower the forming limit and the higher the fracture risk.(2)If the flow of the round billet is uniform,the tensile stress in the deformation zone will be reduced and the forming limit will be increased.(3)The material with better plasticity and lower yield ratio can reduce the deformation resistance and increase the forming limit.(4)Reducing friction coefficient can reduce tensile stress,reduce deformation resistance and friction resistance in deformation area,increase forming limit and improve surface wrinkling.(5)Using drawbead to increase the flow resistance of the material into the die,increase the radial tensile stress and reduce the tangential compressive stress can prevent the surface of the blank and the flange from wrinkling. |
