Experimental Analysis of Cryogenic-Treated Single Tubular Electrodes in Micro-EDM Using CRITIC-MOORA Based Integrated Approach

Abstract

The current research focuses on the viability of rotating, single tubular brass electrodes undergoing shallow cryogenic treatment (at -140°C) before micro-drilling austenitic stainless steel SS316L with the electrical discharge machining process. In order to study and achieve a better rate of material removal and a lower rate of electrode wear, the Taguchi L18 experimental matrix representing the four variables, current, duty cycle, capacitance level, and gap voltage was examined. Regular tap water served as the dielectric fluid to uphold the sustainability concept of the machining experiments and an integrated hybrid approach incorporating CRITIC (criteria importance through inter-criteria correlation) weight determination method and MOORA (multi-objective optimization by the ratio analysis) was applied for decision making. The weight fractions (significance) for MRR and EWR were found to be 0.5532 and 0.4467, respectively and the MOORA method converted multiple objective parameters into a single objective function with weight fractions assigned to each of them. An ideal parameter combination highlighting the dominant significance of duty cycle, pulse current, capacitance level and gap voltage with corresponding values of 70%-18A-1-34V was obtained and the results were substantiated with relevant confirmation experiments. The highest MRR achieved is 10.0961 mm³/min and the lowest EWR is found to be 3.9640 mm³/min. Moreover, the electrode tip regions, the micro holes, and the surrounding workpiece surfaces were also thoughtfully scrutinized and contrasted using scanning electron micrographs (SEM), which validates the worth and significance of cryogenically frozen electrodes in successful micro-drilling of SS316L material.