Understanding the influence of servo-press kinematics on a sheet metal forming process using a simulation-based approach

Abstract

The capabilities offered by the servo-presses are not fully exploited by the sheet metal forming companies due to the lack of knowledge of their influence on the forming processes. Indeed, the control of the beneficial effects and the full use of servo-press features, such as the programmable kinematics, are increasingly becoming concerns for the companies having acquired that type of press. In this context, the finite element simulation is undoubtedly an approach to evaluate the potential gains generated by those presses and to validate the servo-press kinematics.This study is an attempt to gain insight into the impact of servo-press kinematics on a sheet metal forming feasibility. The forming experiments presented in this study have been carried out by CETIM for a X2CrNi18-09 stainless steel. The numerical simulation has been performed with AutoForm software that enables the user to rapidly and accurately design and simulate the sheet metal forming processes, including stamping operations. All parameters influencing the stamping operation in a servo-press can be considered. They include, for example, press kinematics, sheet temperature variation during the forming process and of course material mechanical properties. The hardening curves of the studied stainless steel at different strain rates and different temperatures have been taken into account. The simulation has been carried out for two servo-press kinematics: sinusoidal and soft-touch. The feasibility criterion, i.e. the part drawing depth, has been defined to match the experimental results. The numerical simulation with AutoForm made it possible to highlight the thermal effects, in particular, the maximum temperatures reached during the drawing operation. The simulation results analysis allowed the user to optimize the motion curve of the press in order to have a minimum cycle time while respecting the lowest possible temperature the sheet might reach during a drawing operation. Thanks to this study, the sheet metal forming companies will therefore benefit from this technology to develop and optimize the servo-presses usage.