A variable force binder for a draw press

Improvements in manufacturing quality, flexibility, and efficiency require innovations in both tooling technology and process control strategies to speed the transition from art to part. An innovative forming press using a variable force binder (VFB) is proposed as the first step in attaining these goals. This paper presents the design, development and qualification of a VFB for a deep-drawing forming operation. The VFB is capable of varying the binder force profile both spatially and temporally, allowing for a complete customization of the binder force profile. The benchmark axisymmetric cup-forming experiment serves as a proving ground for demonstrating the VFB's performance. Experimental results illustrate the VFB's ability to regulate material flow at localized regions around the blank perimeter. An electrohydraulic control system has been designed and implemented to track predetermined binder force trajectories in real time. Tracking performance is illustrated and explained. A quantitative measurement technique for describing the end product, i.e. the drawn cup, is presented to provide a standard for error analysis and for future work developing closed-loop process control strategies. (C) 1998 Elsevier Science S.A.