Electric discharge machine is a non-conventional machining. In which there is no contact between tool and work piece. By EDM process machining of hard material components that are difficult to machine such as heat treated tool steels, ceramics, composites, carbides, heat resistance steel which are used in die and mould producing industries, aero space and nuclear industries. In the work, the machining parameters for thesis are current, pulse on time and pulse off time, which are optimized for

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... nimum tool wear rate (TWR), maximum material removal rate (MRR) and minimum surface roughness during electro discharge machining of EN-31. Analysis of Variance is also used to find out variable affecting the various responses mentioned above. I. INTRODUCTION EDM or electric discharge machining is completed when a discharge take place between anode and cathode, due to discharge the intense heat energy is produced near the zone. That is sufficient to melt and evaporate the materials in the sparking zone. To improve the effectiveness of the process, a die electric fluid (hydrocarbon or mineral oils) is used in this work piece and the tool is submerged. It has been observed in the process that if both the electrodes are of same material, the electrode connected to positive terminal generally erodes at a faster rate than the other. Due to this, the work piece is normally made the anode. A suitable gap, known as spark gap, should be maintained between the tool and the work surfaces to complete the process. Since the spark occurs at the place where the tool and the work surface are the close enough and after each spark the spot changes (due to the material removal after each spark), the spark travels all over the surface. This is the reason of uniform material removal all over the surface, and finally work piece conforms to the tool surface. A study conducted was by Subramanian Gopalakannan and Thiagarajan Senthilvelan [1] to observed the effect of pulsed current on material removal rate, electrode wear, surface roughness and diameter overcut in corrosion resistant stainless steels viz., 316 L and 17-4 PH. The materials used in the work were machined with different electrode materials such as graphite, , copper-tungsten & copper. It is observed that the output parameters such as material removal rate, electrode wear and surface roughness of EDM increases with increase in pulsed current. The final result obtained that the high material removal rate have been obtained with copper electrode whereas copper-tungsten yielded minimum electrode wear, smooth surface finish and good dimensional accuracy. The study of Pravin R. Kubade and V. S. Jadhav [2] investigated the effect of EDM parameters on EWR, MRR and ROC while machining of AISI D3 material with a copper electrode. The parameters considered were pulse-on time (Ton), peak current (Ip), duty factor (t) and gap voltage (Vg). It is found that the MRR is mainly influenced by peak current where as other the other factors used, have very less effect on material removal rate. Electrode wear rate is mainly influenced by peak current and pulse on time, duty cycle and gap voltage has very less effect on electrode wear rate. Peak current has the most influence on radial overcut then followed by duty cycle and pulse on time with almost very less influence by gap voltage. To study the effected process parameters and electrode shape configuration on the machining parameter such as surface quality, electrode wear & material removal rate Shishir Mohan Shrivastava and A.K. Sarathe [3] conducted experiments and found better machining performance was obtained generally with the electrode as the cathode and the work-piece as an anode and it was observe that for high MRR main process parameters are peak current, pulse on time ,pulse off time, whereas for electrode wear were mainly influenced by peak current and pulse on time. Surface quality of the work was mainly influenced by peak current. The tool shape configuration concerned best tool shape for higher MRR and lower TWR is circular, followed by square, triangular, rectangular, and diamond cross sections. In a research, Abhishek Gaikwad, Amit Tiwari, Amit Kumar and Dhananjay Singh [4] studied the effect of control factors (i.e., current, pulse on time, pulse off time, fluid pressure) for maximum material removal rate (MRR) and minimum electrode wear rate (EWR) for EDM of hard material Stainless steel 316 with copper as cutting tool electrode. In this paper both the