Machining Performance Optimization During Electro Discharge Machining on Titanium (Grade 4): Application of Satisfaction Function and Distance-Based Approach

Abstract

Titanium grade-4 (3.7065, R50700) is one of the most robust materials and finds its application in aerospace industry specially for making spacecraft, aircraft, missiles, naval ships, armor plating, etc. The main advantage of titanium is that it has a high strength, low-density results in less weight. It can withstand very high temperatures also. Machining of titanium was not an easy task, as it is a very hard material and it has poor thermal conductivity, higher pressure load, non-uniform chip thickness, etc. So we have chosen electro discharge machine (EDM) for the machining of titanium workpiece. Our aim was by taking peak current (I_p), pulse on time (T_on), and voltage gap (V_g) as input control parameters based on L₉ orthogonal array, to find optimum values of response parameters such as material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR). In this research, work satisfaction function has been used to obtain the individual satisfaction values of the responses, and then these multi-responses have been converted into an equivalent single index. A distance measure has been computed next which basically determines the separation of each experimental setting (alternative) with respect to the ideal expectation (satisfaction). Finally, this distance function has been optimized (minimized) by Taguchi method.