Multi-objective parametric optimization using the Grey-Taguchi approach for powder mixed electric discharge machining of grade-II titanium alloy with cryogenically treated electrodes

Electric discharge machining (EDM) is a widely accepted non-conventional machining process used for machining hard and difficult-to-machine materials by ordinary machining process. In the present work, powder mixed electric discharge machining (PMEDM) of titanium alloy (grade-II) with cryogenically treated electrodes was performed. In this paper, an attempt has been made to optimize the EDM process parameters of titanium work-piece using Grey-Taguchi approach. Experiments have been conducted under different conditions of pulse-on-time, peak current, electrode materials (copper, copper-chromium and copper-tungsten) and cryogenic treatment of electrode material. The machining characteristics such as metal removal rate (MRR), tool wear rate (TWR), surface roughness (SR) and micro-hardness (MH) are selected as the quality targets. Nine experimental runs based on L-9 orthogonal array of the Taguchi design of experiment are performed. An optimal parameter combination of the EDM was obtained through grey relational analysis (GRA). The analysis of variance (ANOVA) as applied to determine the level of significance of process parameters and it is found that peak current is the most significant factor for the machining of titanium. A confirmation experiment is performed to verify the optimum process parameter condition. Experimental results show that multi-response characteristics can be improved significantly through grey relational analysis. The validation experiment show an improved material removal rate of 5.2%, surface roughness of 4.92% and micro hardness of 12.84% when Grey-Taguchi approach is used. Though, slightly increase of 2.95% in tool wear rate is observed.