Improvement of product quality using negative clearance grooved punch

Abstract

Center cracks frequently occur during extrusion cutting. These cracks are often caused by uneven material flow velocities, which may also increase the material's hardness and cause surface fractures and unevenness. In this study, simulations and experiments were performed to determine whether a novel grooved punch can stabilize the material flow velocity of a billet during extrusion cutting. The relationship between the punch and die outlet geometry was also investigated. If the punch dimensions are smaller than those of the die outlet, the product shrinks and fractures. Larger punches can prevent these defects but increase the material flow velocity, causing sinking at the center. Finite element analysis and experiments conducted with grooved punches revealed that both shallow and deep grooves can improve the control of material flow and delay acceleration. Punches with greater volume both increase and stabilize the material's acceleration. The dimensions of the grooved punch must be similar to those of the die outlet to ensure optimal material flow.