Effects of Wire Surface Roughness on Wire EDM Characteristics

Abstract

The purpose of this study is to develop a new type of coated wire electrode for fine wire EDM. Piano wire with a very high tensile strength is coated with an electrically conductive brass layer to achieve high-speed and high-precision wire EDM. In our previous papers, using a thin wire of 50μm diameter, the thickness and quality of the brass coating layer were optimized and the effects of the tensile strength of the piano wire used as the core wire on machining characteristics were discussed. In this paper, the effect of surface roughness of the brass wire electrode was experimentally investigated. As a result, it was found that by using wire with relatively large surface roughness, the machining rate increased because of the high discharge frequency. Also, a more uniform distribution of the discharge location was confirmed by high-speed observation of the working gap during the process. In addition, the electrostatic field in the gap between the wire electrode and workpiece surface was analyzed and the reason for the high machining rate in case of the wire with relatively large surface roughness was discussed from the viewpoint of the distribution of electric intensity distribution on the wire surface.