Simultaneous improvement of Z-coordinate and overcut in EDM of titanium grade 5 alloy using a carbon-coated micro-tool electrode

Depth of machining and dimensional accuracy are important parameters in assessing the quality of microelectrical discharge machining (EDM); therefore, enhancement of these two entities is highly essential. The optimal process parameters in microEDM are significantly influenced by the electrode material, which directly affects the machining quality. In this study, depth of machining (Z co-ordinate) and overcut (OVC) in microEDM with carbon-coated electrode were selected; and capacitance (C), voltage (V), and rotary tool (RT) were the process parameters. The experimental work was performed on a titanium alloy (Ti-6 Al-4 V) with a thin film-coated microtool electrode. The surface of the tungsten carbide microtool electrode was coated with carbon and the thickness of the coating was approximately five microns. The results show that the Taguchi-multi-objective optimization based on ratio analysis (MOORA) - analytic hierarchy process (AHP) is the best combination for performing a simple and concise calculation in the machining process; and U = 140 V results in higher machining efficiency with C = 10000 pF and RT = 200 rpm. Our results show that the quality of the machined surface and machining accuracy in microEDM using coated electrode at optimal parameters are good.