Study on pilot hole deformation by punching

Abstract

Progressive die has some forming stages. The feeding of sheet material is necessary to obtain a forming product. In general, the sheet material used in the forming process is located using a pilot pin and pilot hole. It is important for keeping feeding accuracy that the deformation of the pilot hole is decreased in the punching stage of progressive die forming. In this paper, the deformation of a pilot hole by punching is discussed on the basis of the results of an experiment. A pilot hole and pilot pin were deformed by punching under various experimental conditions in this study. The deformation of the pilot hole and pilot pin decreased with increasing distance between the punch and pilot hole. Increasing the distance between the pilot pin and punch was effective for decreasing the dimensional changes of the pilot hole and the deflection of the pilot pin. The material flow in the lateral direction was observed using indentations produced by a micro-Vickers hardness testing machine. The material flow decreased with increasing distance from the punch. It is concluded that the material flow is useful data for deciding the positions of the pilot hole and pilot pin.