MCDM-Based Optimization of Performance Characteristics During µEDMing of SS 304

Experimental Set Up And Procedure

A cylindrical Pure Copper (Cu) rod of 430µm as tool electrode tip diameter with 30-40mm length and SS 304 sheet of 1cm×1cm size with 300µm thickness as workpiece material were taken during the micro-EDM process. A new tool electrode was used for each set of experiments. Tool tip diameter was measured by Mitituyo digital micrometer and circularity was examined by Leica Optical Microscope and corrected with fine emery paper. Machined micro holes on SS 304 were measured using Leica Optical Microscope. Hole diameter was calculated taking average diameters of all 3 micro holes for each set of experiments. Experiments were carried out on ELECTRONICA ZNC EDM machine with SZNC V5 control panel. A total of 20 sets of experiments have been done with 3 number of experiments in each set using central composite design based on Response Surface Methodology with coded values as -1.682 (-α), -1, 0, 1, +1.682 (α).Genetic Algorithm based optimization and regression analysis have been conducted to establish a mathematical relationship between MRR, TWR, Overcut and Peak current, Pulse on Time, Flushing pressure. Gap current, Pulse On-time and Flushing pressure have been selected from 1-10A, 1-10µs and 0.05-0.5 kg/cm2 respectively. Gap voltage and servo voltage have been kept fixed at 40V and 45V respectively. Pulse Off Time has been kept fixed at 5µsec. Analysis of experiments have been done based on contour plots where values are encoded in coded units where values coded as 0 represent the mid values. Negative coded values represent lower ranges from mid value and positive coded values represent higher ranges of values. Actual values of process parameters against coded values are as shown in Table 1.