Molecular dynamics study on the effect of discharge on adjacent craters on micro EDMed surface

Using molecular dynamics simulation (MDS), investigation was carried out to understand the mechanism of material removal during the formation of overlapping craters on surfaces obtained by micro electrical discharge machining (MEDM) and their effect on the crater surface. Apart from overlapping craters, two other cases were also considered viz. craters separated by a finite distance and craters coinciding at the periphery since these two will mostly occur during initial phase of machining. In all cases, the material removal was due to melting and vaporisation; it was also observed that the amount of material removal by vaporisation increased from 36% (approx.) in 1st discharge to 44% (approx.) in the 2nd discharge due to ease of vaporising the amorphous layer formed after the 1st discharge. Moreover, final crater size viz. depth and diameter obtained in the 1st crater measured at the end of MDS was relatively less as compared to 2nd crater. The increase in crater depth and diameter increased with reduction in distance between discharges. The increase in diameter of 2nd crater with respect to 1st crater for all the three cases was observed both during MDS and on the actual surface generated by MEDM.