Research of the plastic status parameter and instantaneous clearance of a punching without burr

This article mainly discusses the characteristic of common and fine punching and the quality of the sheared edge. Although common punching has been applied widely, the quality of the sheared edge is very poor. Fine punching work-piece is better in terms of quality, but it still is not being applied widely because the structure of the die is complicated and the manufacture of die and using a pressure machine are both expensive. A new fine punching processing without burr is put forward by discussing the plastic state and compressive stress state of the material which influences the quality of the punching workpiece in the deformation zone. It provides the plastic status of material to determine the parameter in the new processing and presents the maximum value of plastic deformation specific energy when the material reaches the plastic state. The authors have analyzed the initial clearance and the instantaneous clearance of ordinary punching. The instantaneous clearance of the ordinary punching process is unstable. By studying this, the authors have introduced a kind of punching process in which the initial clearance and instantaneous clearance are stable, namely, the negative clearance fine punching process. Because of using the negative clearance fine punching process, the material of the sheared distorting section comes into the plastic state. The surface quality of the punching sheared edge is improved by 1.5 times compared to that of ordinary punching. The recommended value of the depth of the negative clearance is given in this article.