Transition surface design for blank holder in multi-point forming

During the last decades, the manufacturing mode and level of industry have been improving from mass production manufacturing to responsive and flexible manufacturing. Multi-point forming (MPF) is a flexible manufacturing technique, which is made up of a set of adjustable base elements controlled by MPF-CAD/CAM software. It uses discrete punches to express a continuous 3-D surface, by which the workpiece's surface under manufacturing is formed. With respect to the characteristics of MPF, two methods for NURBS surface extension are presented in this paper to design the blending surface between the surfaces of the blank holder and the workpiece. Two design approaches of transition surface are proposed: one is a flexible surface extension, and the other is a bridge surface extension. These two algorithms, through which the transition surface designed can reach G2 continuity, are both effective and reliable. Applications show that high-quality products are manufactured in MPF by this transition surface design. (C) 2005 Elsevier Ltd. All rights reserved.