A stamp forming die, whose flexible blank holder was designed using FEA, was built. Tests were performed to evaluate the robustness of the die once closed-loop control was implemented. These results were compared to the results of open-loop tests presented earlier. The closed-loop tests were designed to determine the die and control system’s ability to reject process disturbances and demonstrate improved robustness in stamp forming when using a flexible blank holder and closed-loop control. Draw beads were used to control local punch forces and blank holder forces were used to control wrinkling. Experimental tests for the die demonstrated that closed-loop control of local punch forces using active draw beads improves robustness of the die. Two different lubricants and varying quantities of lubricant were evaluated for this study. Additionally, the ability to simultaneously use draw bead height to control local punch force and blank holder force to control wrinkles was demonstrated.

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