Observation of Material Removal Process by Single Pulse Discharge in Air

Abstract

 Although electrical discharge machining (EDM) can be used to perform high-precision machining, the material removal rate is low. From this viewpoint, it is extremely important to understand the process by which material is removed in the EDM method. In this study, the state of a workpiece being processed by a single pulse discharge was observed using a high-speed camera equipped with a high-magnification lens. To enable easy observation of the behavior of the material, a machining condition was selected in which there was a long duration of the pulse discharged by the needle electrode in air. Using a laser beam as illumination, an observation system employing a bandpass filter that allowed only a specific wavelength to pass through it was constructed. As a result, the behavior of the workpiece during the discharge could be observed without the effect of plasma emission. It was observed that several explosions intermittently occurred on the positive side of the workpiece during a single pulse discharge duration. Consequently, several small craters superposed in a narrow region were observed.