Research On Key Technologies Of Large Complicated Multi-position Progressive Stamping

Automobile industry has become the pillar industry of national economy in our country.The level of the car manufacturing technology is represented by that of the stamping die atsome level for that auto parts are mainly formed by stamping, and multi-position progressivedie is used by more and more manufacturers to realize the automatic production, to improvethe production efficiency and reduce the cost. However, lack of independent developmentability of large complex multi-position progressive die is the problem which automobileindustry and parts production companies face with. The die development status needing torepeatedly test and repair can be changed by effectively using numerical simulation to solvekey technical problems in the design and manufacture process of multistep progressive die, sothe technology and market competitiveness of manufacturers can be improved.The VW automobile door glass guide rail researched in this paper has large size,complicated shape and high forming precision. The stamping technology and overall structureof the progressive die was designed, and then the finite element numerical simulation of chainof processes including bending-drawing, trimming, sizing, flanging and springback wereaccomplished by using Dynaform. As well, in this paper, optimum flanging blank(trimmingline) design and stamping quality control of the guide rail was studied based on the numericalsimulation, and the forming defects like carrier distortion, crack and springback werepredicted. Then the validity and rationality of the numerical simulation was verified byexperimental research. The main research contents and conclusions of this paper aresummarized as follows:（1）The middle shape was built for simultaneous sheet metal forming of left and right guiderail, according to the symmetry characteristic. One-step formability analysis and blank designwas accomplished by using inverse approach method. The13-positions progressive stampingprocesses for manufacturing the part was determined, and the double-row layout with bilateralcarrier of uniform width was finally designed. Then the overall structure of progressive diewas designed.（2）The inverse calculation model of flanges unfolding on the complex surface was built.The initial approximate rimming line was obtained by manually accurately selecting the sheetelements and unfolding it on to many complex surfaces connected with right-angles. Then theforward finite element simulation results were compared with the ideal height of guide rail,and optimum accurate trimming line for flanging was calculated by iteratively optimizing anddecreasing the height error. （3）The methods of multi-position progressive stamping simulation were compared and theapplicability was analyzed. According to the shape of the guide rail structure parts and thecharacteristic that there is no deformation interaction between the adjacent stations pieces, themethod of single-station and multi-process was chose to simulate the progressive stamping toensure the stamping and springback simulated accurately and successfully.（4）The multi-process of progressive stamping of guide rail structural member wassimulated based on the method of single-station and multi-process. The forming defectsoccurred by irrational die structure or process design could be predicted based on thenumerical simulation, and then measures were taken by analyzing the causes so that theforming quality of parts can be improved.（5）The workpiece springback of large complex structural part was predicted after sheetmetal forming process simulation. According to the position with large springback afterunloading or high accuracy, the workpiece was segmentally trimmed and the springback canbe effectively controlled by sizing with inlaying structure after the internal stress released.（6）The progressive stamping test results of rail structure show that the forming defects likecarrier distortion, forming crack have been solved well through the studies of stampingquality control. Thickness of bending-deep drawing piece was measured and compared withthe simulated values, and the maximum relative error is only2.7%; and the simulation resultof springback prediction was verification by actual measurement. And the results prove thatthe forming and springback simulation model is reliable and can provide guidance for theactual production.