Framework for Simulation-Driven Design of Stamping Dies Considering Elastic Die and Press Deformations

Sheet metal forming (SMF) simulations are used extensively throughout the development phase of industrial stamping dies. In these SMF simulations, the die and press are normally considered as rigid. Previous research has however shown that elastic deformation in these parts has a significant negative impact on process performance. This paper demonstrates methods for counteracting these negative effects, with a high potential for improved production support and a reduced lead time through a shorter try-out process. A structural finite element model (FE-model) of a simplified die is studied. To account for elastic deformation, the blankholder surfaces are first virtually reworked by adjusting the nodal positions on the die surfaces attaining a pressure distribution in accordance to the design phase SMF simulations with rigid surfaces. The elastic FE-model with reworked surfaces then represents a stamping die in running production. The die is now assumed to be exposed to changed process conditions giving an undesired blankholder pressure distribution. The changed process conditions could for example be due to a change of press line. An optimization routine is applied to compensate the negative effects of the new process conditions. The optimization routine uses the contact forces acting on the shims of the spacer blocks and cushion pins as optimization variables. A flexible simulation environment using MATLAB and ABAQUS is used. ABAQUS is executed from MATLAB and the results are automatically read back into MATLAB. The suggested optimization procedure reaches a pressure distribution very similar to the initial distribution assumed to be the optimum, and thereby verifying the method. Further research is needed for a method to transform the calculated forces in the optimization routine back to shims thicknesses. Furthermore, the optimization time is relatively long and needs to be reduced in the future for the method to reach its full potential.