Comparisons of single pulse discharge crater geometries in EDM and EAM

Abstract

Electrical discharge machining (EDM) and emerging electro-arc machining (EAM) are machining processes sharing a similar material erosion mechanism. However, the input parameters and the output responses of them exhibit significant differences. To gain a deeper understanding of these differences, a study was performed adopting single pulse discharges and machining parameters covering EDM and EAM. A full factorial experiment including 50 trials with consideration of the polarity, the discharge current, and the pulse duration, was designed and carried out. For more detailed research and for the sake of comparison, the trials were divided into die-sinking EDM, short pulse EAM, normal EAM, and low current EAM. While the crater geometries including the heat affected zone diameter, the crater depth, the white layer thickness, the removal volume, and the removal ratio, were acquired as results and analyzed. The heat affected zone diameter under both polarities grew with increasing the discharge current and longer the pulse duration. The crater geometry of EDM and EAM was similar when positive polarity was adopted. The crater under negative polarity became shallower as the discharge current decreased and as the pulse duration increased: this led to a significant difference between EDM and EAM. Furthermore, the removal volume and the removal ratio exhibited similar trends. The shallow craters of negative polarity with little removal volume were likely to appear in the normal EAM and low current EAM trials. The characteristics of EAM are such that the high discharge current and the long pulse duration together result in a large material removal rate (MRR) while the long pulse duration alone results in a low electrode wear ratio (EWR). However, the removal ratio of EAM is lower than that of EDM.