Pulsed Power Supply Superposed with RF Oscillating Wave for the Improvement of Micro EDM Process

During the micro electrical discharge machining (micro EDM) process, the dielectric property of narrow interelectrode gap is transiently changing. With the hysteretic servo motion of spindle, the effective discharge ratio (EDR) between electrodes is low. In this research, a pulsed power supply superposed with the radio-frequency (RF) oscillating wave of controllable frequency and amplitude is proposed in order to induce interelectrode continuous discharge, so that the machining efficiency and accuracy are improved simultaneously. The experimental results of micro-hole machining shows that under the oscillating frequency of 160 MHz and amplitude of ±10 V, the machining efficiency is increased by 35%, the tool electrode wear rate (TWR) remains almost unchanged, and the taper error of micro-hole is reduced by 43%. Furthermore, the process of relatively enlarging discharge gap range and increasing number of discharges after superposition is discussed, and the proper superposed oscillating amplitude is identified.