Study on arc plasma movement and its effect on crater morphology during single-pulse discharge in EDM

In electrical discharge machining (EDM), the arc plasma plays an important role in material removal and crater formation. However, the dynamic characteristics of arc plasma during the machining still have a lack of attention. In this study, a high-speed camera and an image processing method were applied to investigate the arc plasma movement behavior with respect to crater formation during single-pulse discharge. The results showed that when the tool electrode was copper and workpiece was steel, with different workpiece polarities, the arc plasma moving speed and moving range changed and thus different crater morphologies were generated. A larger discharge current and narrower gap distance caused more intense arc plasma movement, thus influencing the crater morphology. Changes in the electrode end shape could influence the arc plasma movement and shape, and the movement of arc plasma would be restricted when the discharge was conducted in oil compared with discharging in air.