Development of Long-Life Heading Tool with Stress Reduction Structure

Abstract

In recent years, a decrease in tool life has been observed in the manufacturing of small screws for precision instruments by cold heading because of the complication of the head shape and hard workpiece material. Thus, remarkable cost saving and high productivity could be achieved by increasing the tool life used in the cold heading of screws such as an M2 pan head screw made of SWCH16A. The prevalent methods of improving the tool life are related to the wear or stiffness enhancement of the tool. In the present study, we propose a method of improving the tool life related to the elastic strain energy absorbed by the tool. First, we analyzed the heading tool for forming the M2 pan head screw, which had a structure configuration for reducing stress in the tool, using the finite element method (FEM) code. Second, the dimensions of the structure configuration of the tool with a hollow section were optimized by FEM analysis. Then, the tool life was increased successfully. The tool life of the developed heading tool was increased 3.7 times compared with that of a conventional heading tool.