Parametric optimization of graphite powder-mixed electrical discharge machining of Ni-Cr dental alloy by response surface methodology

In this study, the effects of machining parameters on material removal rate (MRR), electrode wear rate (EWR) and surface roughness (R_a) in the electrical discharge machining (EDM) of nickel-chromium-based alloy were investigated. Discharge current (I), pulse-on time (T_on), pulse-off time (T_off) and graphite powder concentration were selected as variable parameters in the study. An experimental setup was designed and manufactured for use in powder-mixed EDM experiments. Mathematical models were generated using response surface methodology (RSM), the most effective parameters on the results were determined and regression equations were obtained. Parameter optimization was performed with the highest MRR, lowest EWR, and lowest R_a performance targets. The ideal machining conditions were determined as I = 12.5 A, T_on=66µs, T_off=6µs and powder-mixed dielectric. Using the powder-mixed dielectric, 34.54% higher MRR, 20.01% lower EWR and 12.64% lower R_a were achieved on average. Using the created mathematical model, the result of the machining to be done with these parameters was predicted and the reliability of the model was tested by comparing the predicted results of the model and the results of the verification experiment.