Optimization of process parameters in micro-EDM of Ti-6Al-4V based on full factorial design

The objective of this study was to investigate the effects of the micro-electro-discharge machining (micro-EDM) process parameters on the machining performance parameters, in order to understand the behavior of each process parameter as well as to find out their optimal values. This research was conducted through a series of experiments using full factorial design. Analysis of variance (ANOVA) and multivariate analysis of variance (MANOVA) were employed to analyze the findings and to determine the significance of each process parameters on the response variables. The process parameters included in this study were voltage, capacitance, electrode rotational speed, and the electrode coating. Voltage and capacitance were studied separately as well as in combination in terms of the discharge energy. The response variables were consisted of machining time, tool wear, crater size, and surface micro-hardness. The findings indicated that the increase in voltage had a decreasing effect on the machining time, while it increased the crater size. The increase in capacitance resulted in decreased machining time and the tool wear, while it had an increasing effect on the surface micro-hardness. It was found that the effects of titanium nitride (TN) coating and the electrode rotational speed were not statistically significant. There was slight improvement of machining time and accuracy for increasing electrode rotational speed due to improved flushing condition, but very high electrode rotational speed was found to be unsuitable for machining accuracy. The overcut of the micro-holes was found to increase gradually with the increase of voltage and capacitance due to increase in spark gap and discharge duration, respectively. The voltage and the capacitance were found to be the two major parameters influencing the micro-EDM performance. Assuming that the importance and the weight of all response variables had been identical, the optimal process parameters for improved micro-EDM of Ti-6Al-4V were found to be TN-coated electrode, 60 V, 4700 pF, and 3000 rpm.