Effect of dielectric conductivity on micro-electrical discharge machining plasma characteristics using optical emission spectroscopy

Electrical conductivity of the dielectric liquid has been shown to play main role in discharge initiation and electrical breakdown as revealed by several modeling and experimental studies on electrical discharges in liquids. However, there has been lack of systematic efforts to evaluate how dielectric conductivity affects the micro-electrical discharge machining (micro-EDM) process, in particular. Experimental investigation has been carried out to understand the effect of dielectric conductivity on micro-EDM plasma characteristics using optical emission spectroscopy. Plasma temperature and electron density estimations have been obtained at five levels of electrical conductivity of water. It is found that while the plasma temperature shows a marginal decrease, electron density of the plasma increases with an increase in the conductivity. At increased electron density, a higher heat flux at anode can be expected resulting in increased material erosion.