In general, deep microholes machined by EDM make machinig efficiency decline because the discharge becomes unstable by EDMed sludge stagnation. In this study, using ultrasonic vibration in machining fluid in order to prevent EDMed sludge stagnation, machining depth, machining rate and behavior of sludges were investigated. As a result of the experiment, the depth of microholes by EDM with ultrasonic vibration became as about two times as that without ultrasonic vibration and machining rate increased. It was observed that EDM with ultrasonic vibration promoted to reject the sludge around the hole.
