SIMULTANEOUS OPTIMIZATION OF µ-EDM PARAMETERS FOR MACHINING INCONEL 718 SUPER ALLOY

This investigation integrated Gray Relational Analysis (GRA) and Taguchi's robust optimization techniques for simultaneous optimization of micro-electric discharge machining (µ-EDM) parameters for drilling micro holes on Inconel 718 super alloy. Voltage, current, duty cycle and pulse-on time are chosen as the most significant µ-EDM variables while the tool wear rate, recast layer thickness, material removal rate (MRR) are treated as the process quality indicating responses. The machining experiments are planned according to Taguchi's L27 design of experiments. Since the measured process are conflicting in nature for the chosen process variables, the problem is treated as the multi-objective optimization problem to simultaneously minimize the tool wear rate and recast layer thickness and maximise the metal removal rate. As the Taguchi's maximum quality optimization alone cannot deal with the simultaneous optimization of multiple process quality responses, the GRA is introduced in this work to consolidate the three process responses as single process quality indicator such as gray relational grade. Consequently the derived gray relational grade was maximised by implementing the Taguchi optimization approach. Further, analysis of variance was used to analyse the significance of the process variables on the process overall performance