Measurement of discharge reaction force under different discharge conditions in WEDM using Hopkinson bar method

Abstract

This paper reports the measurement of discharge reaction force with respect to the discharge bubble in wire electrical discharge machining (WEDM) using the horizontal Hopkinson bar method. Using an RC discharge pulse generator circuit which is of the single pulse control functionality, independent discharges are ignited in the gap between the wire electrode and end face of the Hopkinson bar while deionized water is continuously flushed. The reaction force acting on the Hopkinson bar from a single discharge was measured without the interference of subsequent discharges. The peak value of measured discharge reaction force reached several Newtons level in both finishing and roughing. The waveform patterns of discharge reaction force in WEDM were found to be significantly different from that in sinking EDM. The first peak of the force acting on the Hopkinson bar was found to be equivalent to the force acting on the wire electrode based on the observation of the interelectrode gap using a high-speed camera. Moreover, the influences of different discharge conditions on the force were investigated.