Effect of Low Frequency Vibration on Micro EDM Drilling

A micro hole is a basic feature in micro manufacturing. Micro electrical discharge machining (EDM) is one of the key techniques for machining micro holes in metallic materials. Since debris is accumulated in the discharging gap between the tool electrode and the workpiece, it becomes increasingly very difficult to machine a micro hole as the chosen diameter is progressively decreased or the depth increased. The use of vibration in micro EDM drilling can improve machining efficiency by refreshing dielectric fluids and flushing out the debris from the gap. Although ultrasonic vibration over a few kHz has been introduced in many applications of micro EDM, it is difficult to apply to a workpiece of a very large size or mass. In this study, the effect of very-low-frequency vibration was investigated to improve the efficiency of micro EDM. Low-frequency vibration in the range of 10 to 70 Hz was applied to single-hole machining, to reverse EDM, and to multiple-hole machining. The machining efficiency was investigated while varying the vibration frequency and amplitude.