Observation of Material Removal by a Single Electrical Discharge: Consideration of Material Properties and Carbon Layer Forming Process

Abstract

Electrical discharge machining (EDM) proceeds by the accumulation of series of single discharges. By combining a band-pass filter and a laser beam, we have constructed a system for observing the discharge gap phenomena in more detail by using the high-speed camera equipped with high-magnification optical lens and we have used this system to observe material behavior during a single discharge. In the present study, single discharge experiments were conducted on steel, zinc alloy, tungsten, copper, and titanium, and the behavior of each of these materials on positive polarity side was examined. With some of these materials, the workpiece was found to be intermittently removed during a single discharge. The mechanism of carbon adhesion to copper is discussed by comparing the contact area between the arc plasma and the workpiece and the size of the discharge crater.