Prevention of wire breakage during wire EDM (3rd report) - discharge location and discharge voltage in case of high current discharge

摘要

Recently used wire EDM machines generate a triangular high peak discharge current of 500 ampere or more. It is very difficult to detect the true discharge voltage, because the discharge voltage is transformed by the influence of the high discharge current and impedance of the wire. In this study, we investigate the variation of discharge location and the discharge voltage immediately before the wire breakage in the case of high discharge current on wire EDM, in order to predict the wire breakage. Three methods that compensate the detected discharge voltage are proposed and the investigated results using these methods are described. It was found that in the case of low discharge current, phenomena immediately before the wire breakage such as local concentration of discharges and increase of short circuits in the gap, are clearly observed, but is difficult to observe them in the case of high discharge current.