Improvement in microhole machining accuracy by polarity changing technique for microelectrode discharge machining on Ti-6Al-4V

A novel technique is presented of changing polarity for microelectrode discharge machining (micro-EDM) in a systematically designed time domain while machining titanium alloy (Ti-6Al-4V) for the fabrication of straight-through microholes. Experimental investigations were made to study precisely the effects of changing polarity in micromachining of Ti-6Al-4V. The experimental investigations revealed that the process parameters of most influence in micro-EDM are peak current I-p and pulse-on time (T-on). These process parameters are heuristically investigated through experiments and their most suitable values are presented in this paper to achieve higher geometrical accuracy in the fabrication of straight-through microholes, which has tremendous applications in biomedical microdevices and automotive, aerospace, and microelectromechanical systems. The material removal rate (MRR), tool wear rate (TWR), overcut (OC), diameter variation at entry and exit (DVEE), and taperness are evaluated. Finally, a new technique of machining straight-through microholes with a set of machining parameters is suggested. A comparative study of constant and changing polarity is also made, and results show that T-on in the range of 1-10 mu s and I-p below 1A with changing polarity are more effective for micro-EDM in improving the machining accuracy of straight-through microholes.