AN EMPIRIC MODEL FOR CONTROLLING SPRINGBACK IN V-DIE BENDING OF SHEET METALS

A process model is presented for v-die bending of sheet metals. This model is especially valuable to control a press brake equipped with a computer integrated controlling and planning system. A bent part recovers elastically on release of load, and the springback varies with both material and process parameters. A desired bend angle is obtained by controlling the punch insertion depth so that the springback can be compensated by right amount of overbending. The model combines analytical method with trial and error work to establish the relationship of punch insertion depths and corresponding unloaded bend angles. To apply this model, three trial bendings are required for sheet metal and tool combination, so that three coefficients in the half-empiric model can be obtained in regressive way. Experiments have shown that process parameters affect springback more obviously than material properties do, and the model predicts accurate punch insertion depths for desired angles in air bending. The model is simple, so it can easily be used for real time control.