Contactless on-line measurement of material flow for closed loop control of deep drawing

The paper presented here introduces a new optical sensor for contactless on-line material flow measurement and its application for closed loop process control in sheet metal forming. The aim of this sensor development was to record the material flow in a closed deep drawing tool during the forming process. The material flow can be utilized as the controlled variable for closed loop control, as this value originates directly from the process and can be used to characterize the process course. Recording of material flow was accomplished contact-free using an optical sensor. A press with a multipoint drawing tool is anticipated within the control loop, in order to generate better the locally varying forces on the blank holder, in accordance with the material flow information. Therefore, the influence of three blank holder systems (rigid, segmented and pliable) on the material flow was investigated for the combination with this multipoint drawing tool. Furthermore, the process boundaries are visualized so as to determine the command variable for the conventional controller, as well as for acquisition of an empirical basis for the fuzzy controller.