Influence of oblique edge blanking on the online punching quality after stretch bending

The oblique edge punching was proposed to reduce the surrounding sag failure occurred under the large punching force during online punching after stretch bending. The finite element models under three different kinds of punches were stablished and the punching processes were simulated by using the DEFORM-3D software. Comparison between the flat-edge punch and the oblique edge punches were realized, and the optimal height of the oblique edge of the unilateral bevelled punch and the single-peak bevelled punch were obtained. Three kinds of punches were designed based on the simulation results, and the experiments for manufacturing the upper strip of the automobile door frame by the online punching after stretch bending were carried out. The results show that the depth of the surrounding sag of punching can be reduced significantly and the appearance quality can be improved effectively by the oblique edge blanking. The effect to reduce the depth of surrounding sag failure by the unilateral bevelled punch is better than that by the single-peak bevelled punch, and the depth of surrounding sag failure on the side near the edge tip of the unilateral bevelled punch is smaller than that on the side away from the edge tip.