Optimization and comparative analysis of silicon and chromium powder-mixed EDM process by TOPSIS technique

Abstract

Powder mixed electric discharge machining (PMEDM) is an advancement in electric discharge machining (EDM) to overcome the problem of low material removal rate and surface finish in the conventional EDM process. In the PMEDM process, metallic or non-metallic powders such as silicon, aluminum, graphite, etc. are mixed in the dielectric fluid. In the present work, Response surface methodology (RSM), in combination with Technique for the order of preference by similarity to ideal solution (TOPSIS) is adopted to effectively optimize the multi-performance characteristics for PMEDM of AISI D2 steel. The electrode used for the study is copper while the powders mixed in the dielectric fluid is silicon and chromium. The effect of input parameters such as current, pulse on time, and powder concentration on material removal rate, tool wear rate and electrode wear ratio is investigated. Analysis of variance (ANOVA) and the main effect plots are generated to determine the significant parameters. For silicon powder-mixed dielectric fluid, the optimum values of current are 8A, pulse on time is 150 µs and powder concentration is 2 g/l while for chromium powder-mixed dielectric fluid, the optimum values of current are 10A, pulse-on time is 200 µs and powder concentration is 2 g/l. The silicon powder-mixed and chromium powder-mixed processes are compared by considering the electrode wear ratio as the response variable. The minimum and average electrode wear ratio for the silicon powder-mixed process is 0.0050 and 0.0093 respectively while for chromium powder-mixed process, the minimum and average values are 0.0025 and 0.0070 respectively. From the comparison, it is evident that the electrode wear ratio is lower for the chromium powder-mixed process.