A Model of Micro Electro-Discharge Machining Plasma Discharge in Deionized Water

For successful commercial adaptation of the mu-EDM (micro electro-discharge machining) process, there is a need to increase the process efficiency by understanding the process mechanism. This paper presents a model of the plasma discharge phase of a single discharge mu-EDM event in deionized water. The plasma discharge is modeled using global model approach in which the plasma is assumed to be spatially uniform, and equations of mass and energy conservation are solved simultaneously along with the dynamics of the plasma bubble growth. Given the input discharge voltage, current and the discharge gap, complete temporal description of the mu-EDM plasma during the discharge time is obtained in terms of the composition of the plasma, temperature of electrons and other species, radius of the plasma bubble and the plasma pressure. For input electric field in the range of 10-2000 MV/m and discharge gap in the range of 0.5-20 mu m, time-averaged electron density of 3.88 x 10(24) m(-3) - 30.33 x 10(24) m(-3) and time-averaged electron temperature of 11,013-29,864 K are predicted. Experimental conditions are simulated and validated against the spectroscopic data from the literature. The output from this model can be used to obtain the amount of heat flux transferred to the electrodes during the mu-EDM process.