Effects of flushing on electrical discharge machining and electro-arc machining

Both electrical discharge machining and electro-arc machining are non-contact machining processes, which use high temperatures produced by discharges to erode material. The gap between the tool and the workpiece is usually filled with liquid dielectric medium. Moreover, liquid flushing is commonly used in the machining processes of electrical discharge machining and electro-arc machining. Much research has been conducted to study the effects of flushing on these processes. However, there has been little study on the mechanism of the flushing procedure for these machining processes. In this article, electrical discharge machining and electro-arc machining experiments adopting different polarities and flow rates were designed and implemented. The plasma tunnel and crater morphology were studied. It was found that the plasma tunnel was lengthened, compressed and broken by flushing in the electro-arc machining experiment; however, the electrical discharge machining experiment did not produce this result. Similarly, tailing discharge craters and polarity effects caused by flushing were observed in the electro-arc machining experiment, while no such performances caused by flushing were found in the electrical discharge machining experiment. The flushing in electro-arc machining was able to reduce the material removal rate, tool wear rate and surface roughness simultaneously, while the effects of flushing in electrical discharge machining were inconspicuous. Moreover, the characteristics of the plasma tunnels of the electro-arc machining experiment were similar to those of arcs, which were different from those of the electrical discharge machining experiment. These results help to verify that the electro-arc machining process adopts arcs, while the electrical discharge machining process adopts sparks, during their respective material removal processes.