Experimental investigation on effective use of machining parameters in electric discharge machining for machining micro-holes in Ti-6Al-4V

The objective of this research work is to machine micro-holes in Ti-6Al-4V alloy using conventional electric discharge machining process and to optimize its machining parameters to achieve maximum material removal rate and minimum electrode wear rate. The process parameters that have been selected for this study were input current (I_p), pulse-on time (T_on) and pulse-off time (T_off). The experiments were carried out based on Box-Behnken L15 design. Using the regression method, mathematical models were developed for output responses (material removal rate and electrode wear rate) and their significance in enhancing machining processes was analysed using surface plots. The input parameters achieving maximum material removal rate was found to be 4 A of input current (I_p), 5.2 µs of pulse-on time (T_on) and 14.4 µs of pulse-off time (T_off), and for achieving minimum electrode wear rate, it was found to be 1 A of input current (I_p), 2 µs of pulse-on time (T_on) and 6.4 µs of pulse-off time (T_off). Further, the multivariate optimization technique, grey relational analysis, was employed to determine the optimal combination of process parameters to maximize material removal rate while minimizing electrode wear rate. The optimum process parameters identified were an input current (I_p) of 1 A, a pulse-on time (T_on) of 8 µs and a pulse-off time (T_off) of 6.4 µs. Experimental results confirmed that these conditions yielded an optimal material removal rate of 0.008 mm³/min and an electrode wear rate of 0.00055 mm³/min. These results confirmed that the optimal values fall within the range of maximum and minimum outputs for material removal rate and electrode wear rate.