Machining characteristics of a hybrid process of EDM in gas combined with ultrasonic vibration

This study integrated the removal mechanisms of electrical discharge machining (EDM) in gas and ultrasonic vibration to explore the benefits of the developed hybrid process in improving the machining characteristics. The developed hybrid process was adopted to determine the machining performances for SKD 61 steel through the experimental investigation. It is well known that using kerosene as a dielectric fluid in EDM would evoke the undesirable problems like fire hazard, air pollution, and environmental damage. In this study, the air, oxygen, and argon gas media were employed in the experiments to investigate the effects on material removal efficiency, surface integrity, and thickness of recast layer. The experimental results show that the hybrid process obtained higher material removal rate (MRR), lower electrode wear rate (EWR), and finer surface roughness (SR). In addition, the oxygen medium could facilitate the reaction within the machining gap to increase the exploding and melting effects. Thus, the MRR obtained by oxygen has the highest values. The argon was an inert gas that could prevent the oxidation during the process, and the lower EWR could be obtained using argon as a medium in the EDM process. The ultrasonic vibration incorporated in the process could effectively reduce the surface defects that were generated on the machined surface. Generally, the different gas media supplied into the machining area could create various mechanisms. The ultrasonic vibration incorporated into the process could also promote the machining performances of the developed hybrid process.