Influence of Machining Parameters on Electro Discharge Machining of NiTi Shape Memory Alloys

NiTi is an alloy of nickel and titanium with important characteristics such as shape memory, superelasticity, high electrical resistance, high corrosion resistance, long fatigue life, and vibration absorption. The unique features of this alloy have made it useful in all types of industries. However due to these same characteristics, it is difficult to perform machining and forming operations on this alloy by traditional methods. One of the machining techniques suitable for NiTi alloy is electro discharge machining. The electro discharge machining process is one of the most practical nontraditional machining methods which are not influenced by the hardness and physical properties of the workpiece. This research intends to study the effects of electro discharge machining parameters such as voltage, discharge current, pulse on time and pulse off time on the rate of material removal, tool wear, relative electrode wear and surface roughness of NiTi alloy. For the design of experiments, the Taguchi's method for the design of experiments, L18 orthogonal array and the 'Minitab' software program have been used. The experiments indicate that the parameters of discharge current, voltage, and pulse on time have a direct impact on material removal rate (MRR), and with their increase, MRR increases as well. Tool wear rate (TWR) diminishes with the increase of pulse off time and discharge current. The analysis of results obtained for surface roughness indicates that pulse on time and off time have the highest impact on the surface roughness of NiTi alloy.