The Bending Method for Sheet Metal Having Widely Thickness Change in More Than Three Times Thickness Range by Press Brake with Variable Punches

Skin sheets of metal aircrafts have complex thickness change patterns. Thus, their forming with press brake is quite difficult. To automate and ensure high quality, a cutting-edge press brake equipment with synchronized material handling system, position variable punches, die, curvature measurement devices, and bending mechanism with curvature feedback/feedforward technology has been developed. In order to determine specifications of many innovative devices such as material handling systems, variable punches, die, etc., and to realize new bending process, a huge number of studies and development have been conducted. Here in this paper, a bending characteristics of Aluminum Alloy 2524-T351 clad and an optimization of each variable punch strokes are described. The bending characteristics are affected by the phase in which only clad aluminum plasticity, the phase in which the clad layer re-yields upon unloading, and the phase in which the base material plasticizes, resulting in a complex curve. It depends on the thickness, die width and previous bending in sequential bending.