Wire spark erosion machining of Ni rich NiTi shape memory alloy for bio-medical applications

The application of NiTi shape memory alloys are growing day by day in biomedical industry. These materials present inherent problems when undergoing conventional machining processes during manufacture of bioimplants. Conventional machining processes require high consumption of energy and resources, and assistance of post processing operations to make high quality implants of shape memory alloys. Unlike conventional methods, nonconventional methods are capable to eliminate the need for post processing amongst other advantages and thus prove to be the most economic means of producing biomedical implants. Wire spark erosion machining (also known as Wire Electro Discharge machining i.e. Wire-EDM) is one such nonconventional machining process that has been explored for the machining of biomedical implants by Ni rich NiTi. The present study aims to analyze and optimize the machinability of Ni55.8Ti shape memory alloy during wire electric discharge machining for biomedical applications. The L16 Orthogonal array using Taguchi design of experiments has been employed for this experimental study. The variable input parameters are namely pulse on time, pulse off time, servo voltage and wire feed rate. Machining at optimum parameters produced good surface finish, high material removal rate and excellent surface integrity. In this paper, specifically, the effect of the aforementioned Wire-EDM parameters on cutting rate, process optimization for the highest cutting rate, and surface roughness obtained at optimum parameters are reported. The outcomes encourage exploring wire spark erosion machining of other shape memory alloys for different scientific and industrial applications.