Robust Design of Deep Drawing Process through In-Line Feedback Control of the Draw-In

In the deep drawing process, the scatter of the friction coefficient between blank and tool interfaces as well as of the material properties between blank positions in the coil or between different coils significantly influences the part quality. These uncontrollable fluctuations increase the risk of waste. To avoid this problem, currently, the new era of Industry 4.0 aims at developing control algorithms able to in-line adjust process parameters and always meet the part quality requirements. Starting from this context, in this study a method for process control during the punch stroke is proposed. It assumes the blank draw-in in specific points as the control variable, while the blank holder force is adopted as an in-line adjustable process parameter. The approach was implemented for the deep drawing of a T-shaped component, using a blank in DC05 steel with a thickness of 0.75 mm. The results show that the measurement of blank draw-in is a representative index of the component quality, which in this study is evaluated in terms of formability (thinning) and cosmetic (surface deflections) defects. Once the optimal condition and the corresponding blank draw-in were identified, the feedback control algorithm was able to increase or reduce the blank holder force according to whether the recorded draw-in was higher or lower than the optimal one.