Characteristics of electrode materials on machining performance of tool steel SKD11 with EDM shinking

Both qualitative and quantitative performance of EDM Shinking process depends not only on process parameters but also on the combination between electrode material and work piece material. This research experimented an EDM machining process uses a different type of electrode material such as cooper, aluminum, steel, brass, stainless steel, bronze and graphite to machine a workpiece of hardened tool steel SKD11. Parameters being analyzed in this research are not only the surface quality but also the material removal rate (MRR), the tool wear rate (TWR), the wear ratio (WR) which is defined as MRR/TWR. The result of the research shows that using different electrode material gives the surface roughness differences less than 3 μm e.g. for pulse current Ip=20A and Ignition voltage Uz=150V using the steel electrode and stainless steel electrode gives maximum Ra 9.63 μm and minimum Ra 6.90 μm respectively or between ISO N9 and N10. In the point of view of quantitative performance, the graphite and brass give the two highest MRR that is almost two times higher than the mild steel and stainless steel electrode. However the brass electrode has a tool wear rate 7.8 times higher than the steel electrode or 5.5 times higher than stainless steel electrode. Therefore it has the lowest wear ratio and even less than 1.0 for Ip=45A. The highest wear ratio is shown by stainless steel electrode with WR=5.23 and the lowest one is by brass electrode with WR=0.9. So, it means the brass electrode is eroded faster than the workpiece. In conclusion the application of the graphite and brass electrodes are normally used for roughing and stainless steel electrode is for finishing process.