Influence of Electrodes and Parameters on Micro-EDM Drilling Performances of 304L Stainless Steel

The current work concerns with studying the effect of micro electrical discharge machining (Micro-EDM) parameters, including; the types of electrodes, the pulse current and the pulse on time on the process responses performances like; material removal rates (MRR), tool wear ratio (TWR), surface roughness (SR), overcut (OC) and the holes taper for micro-EDM holes-drilling of a biomaterial stainless steel 304L workpieces with 250-300 μm dimensions. The experimental results were designed and modeled by using the response surface methodology (RSM), the analysis of variance (ANOVA) and the statistical Expert system 10.0 software program. The results show that the use of higher pulse current up to (16 A) improved the MRR, OC and the taperness of the produced micro-holes, while the use of lower pulse current (8 A) improved the EWR. The using of pulse on duration values up to (75 μs) improved the taperness of the produced micro-holes, while it has fewer influences on the other output parameters. Results also indicated that the MRR reached a maximum value of (0.81×10
^-3
mm
³
/min) when using the copper electrodes. This value is higher by 49.4% than when using the tinned coated copper electrodes. The lower value obtained of EWR when using the graphite electrodes reached (0.01×10
^-3
gm/min). This value is too low when compared with using the copper or tinned coated copper electrodes. The best values of OC obtained when using the tinned coated copper electrodes, reached (-1.89 μm). This value is improved by 23.2% than when using the copper electrodes. The results also show that the best minimum hole taperness obtained when using the copper electrodes (0.31°). This value is lower by 41.9% than when using the tinned coated copper electrodes.