Springback is a major problem in the deep drawing process. When the tools are released after the forming stage, the product springs back due to the action of internal stresses. In many cases the shape deviation is too large and springback compensation is needed: the tools of the deep drawing process are changed so, that the product becomes geometrically accurate after springback. In this paper, two different ways of geometric optimization are presented, the Smooth Displacement Adjustment (SDA) method and the Surface Controlled Overbending (SCO) method. Both methods use results from a finite elements deep drawing simulation for the optimization of the tool shape. The methods are demonstrated on an industrial product. The results are satisfactory, but it is shown that both methods still need to be improved and that the FE simulation needs to become more reliable to allow industrial application.

Now that Finite Element springback prediction has become possible, springback compensation can also be carried out in the context of a forming simulation, before actual production tools are made. The Displacement Adjustment (DA) and Springforward (SF) methods were applied to an analytical bar stretchbending model, in order to gain insight about the influence of material, process and geometrical parameters on springback and compensation. The DA method was investigated in both a one-step and iterative variant. In one-step DA, a compensation factor is required. This factor can be directly calculated for the analytical model. The results can be used as a guideline for industrial processes, where such a calculation is not possible. Finally, it was shown that iterative DA leads to better tool shapes than SF, and that practical and computational problems make the use of SF impossible in an industrial context.

Abstract.Several measures are applied in order to reduce springback but it is not always possible to reduce springback sufficiently. Therefore techniques have been developed to counter springback by modification of the tool shape (overbending). In this paper the smooth displacement adjustment method (SDA) for springback compensation is presented. The discrete springback displacement field is approximated by an L2-projection of suitable continuous smooth functions. Multiplied by a compensation factor the approximating continuous displacement field is applied to the tool surface including the addendum. An application of the new method on an industrial part is demonstrated. The main advantage is the easy handling of the method.

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Abstract. Upon unloading after the forming stage, a sheet metal product will spring back due to internal stresses. Springback is a major problem for process-planning engineers. In industrial practise, deformations due to springback are compensated manually, by doing extensive measurements on prototype parts, and altering the tool geometry by hand. This is a time consuming and costly operation. In this paper the application of two compensation algorithms, based on the finite element simulation of the forming process are discussed. The smooth displacement adjustment (SDA) method and the springforward (SF) method have been applied to several industrial products, such as the NUMISHEET 2005 benchmark#1. With the SDA method successful compensations have been carried out. For the SF method some principal problems remain.