Variable blank holder pressure by magneto-rheological actuators in deep drawing

Deep drawing is one of the most used processes in industry, whose reliability is closely linked to the possibility of adequate control of the blank holder force (BHF). To avoid typical failure mechanisms, such as wrinkling and tearing, it is necessary to properly adjust the BHF during the process. The paper presents the design of a new blank-holding set-up based on magneto-rheological actuators, which allow a flexible adjustment of the force during the process. A closed-loop control, based on the direct detection of the metal sheet displacement under the blank holder, is implemented to regulate in real-time the actuator's load. The obtained experimental test results show that (i) the presented set-up allows to apply blank holder pressures with an average error less than 5% with respect of the target forces; (ii) the low latency times to allow the force variations, and (iii) the possibility to vary in real-time the blank holder load response during the deep drawing.