Clarifying mechanism of determining tool electrode wear ratio in EDM using spectroscopic measurement of vapor density

This paper clarifies the mechanism of determining tool electrode wear ratio in electrical discharge machining (EDM) by spectroscopic measurement of the vapor density of the tool electrode material. The relative density of copper vapor in EDM arc plasma was obtained from radiant fluxes emitted from the arc plasma and the temperature of the arc plasma obtained from the radiant fluxes of two different wavelengths using the line pair method. Longer pulse duration is known to result in lower tool electrode wear ratio and deposition of a thicker carbon layer on the tool electrode surface. On the other hand, the density of copper vapor evaporated from the tool electrode surface was found to be lower when the carbon layer was thicker, indicating that tool electrode wear is prevented by the protective effects of the carbon layer.