A Method To Obtain The Trimming Lines Of Multi-process Parts Based On Finite Element Grid

During sheet metal forming, the determination of shape and dimension oftrimming line is the precondition of drawing up process rules. Appropriate trimmingline can not only effectively change the sheet metal flowability in the forming process,but also obviously improve the wrinkle, crack and other defects and reduce volume ofcutting. Besides, for those forming parts, if we can get the accurate shape anddimension of trimming line, it will reduce the try-out times, shorten the moulddeveloping cycle and save the cost.The grid-mapping method is foreword to acquire the trimming lines ofmulti-process parts based on the finite element method of simulating the flangingprocess. Firstly discretizing the flanging contour line and projecting the obtainedpoints onto the grid model after the flanging simulation. Secondly positions of theprojecting points located on the elements are determined. Finally the new coordinatevalues of the projecting points on flanging blank grid model are acquired through themapping relationship of elements and nodes. The trimming line can be accuratelycalculated after only three or four iterative computations.The original trimming line of parts can be optimized using the methods of thefinite element reverse method and the grid-mapping method. The finite elementreverse method is used to calculate the original trimming line of the optimizationprocess. The method can directly get the original trimming line from the shape of theparts. After that, we can use the grid-mapping method to optimize the originaltrimming line and get the ideal the trimming line.Finally, the grid-mapping method is applied to obtain a trimming line ofautomotive connecting board, which has twice flanging process in the forming.Through optimizing the original trimming line and doing experiment, it is proved toverify this method. In addition, the grid-mapping method can also be used to optimizethe parts which have more than twice flanging process. It is proved that the idealtrimming lines which are obtained using the grid-mapping method can meet therequirements of design and reduce the try-out time and the cost. It also hassignificance to the engineering practice.