Closed Loop Binder Force System
When drawing non-axissymmetric sheet metal parts it is necessary to control the flow of material between the lower and upper binder in such a manner that prevents the occurrence of both tears and wrinkles in the drawn part. One possibility for the control of the material flow is through the deliberate adjustment of the normal forces. If one can measure the flow-in of the material into the die cavity as a function of punch stroke with a special sensor, and if this information can be used to produce an empirical flow-in curve over the stroke for good parts, then it is possible to construct a closed- loop BHF control system. Building such control system is feasible by implementation of special dies with hydraulically supported segmented binders. This system allows an automatic response to a change in the friction conditions.