Parametric optimization of µEDM drilling on titanium using principal component analysis

Titanium (Ti) is a hard and difficult to machine material which has high tensile strength and toughness at extreme temperature. Microelectrical discharge machining (µEDM) is primarily used to machine hard and brittle materials very effectively. In this paper, µEDM drilling is performed on Ti grade 2 alloy using copper as a tool. The parametric effect of voltage, capacitance and feed rate (FR) on response measures such as material removal rate, linear tool wear rate, overcut and taper is investigated after performing full factorial 27 experimental runs. Capacitance and voltage are found to be the most significant factors as compared to FR for all response measures. Micrographic analysis reveals minimum burr formation, recast layer and circularity error to occur at lower level of capacitance and voltage. The quality of microholes deteriorates with increment in capacitance and voltage due to the formation of bigger and deeper craters. An online monitoring is performed by plotting the data of machining time and work feed of the tool movement. Significant short circuiting is observed at lower levels of voltage and capacitance, which results in higher machining time due to lower discharge energy. Further, principal component analysis is employed to find out the weightage value of each response and simultaneously performs optimization of all the responses. Microhole with minimum burr formation, recast layer and circularity error is achieved at highest overall principal component index of 0.263, performed at 120 V, 100 pF and 10 µm/s.