Experimental Study and Optimization of Electric Discharge Machining of Al 7075 alloy Gary _ using the Taguchi Method

In this paper, the accuracy of AL7075 electrical discharge machining was investigated. The experimentation based on Statistical Design of Experiment methodology was conducted by selecting five process inputs including Peak current, Off-time period, Voltage, Discharge time and Polarity with the aim of studying four outputs which are Surface roughness, Material removal rate, Over cut and also, Wear of the tool. The purpose of this research is access to a final machining part with a desirable surface quality along with the minimum possible deviation from nominal tolerances under different parametric settings. The results indicate that the machining quality is functionalized directly through the inputs. Interestingly, the figures related to tool wear is considerable lower than initial expectation of Aluminum EDM. Selection of machining polarity did not have priority on electrode wear here however; other responses were dramatically affected by this factor. Between all of the existed parameters in the process, the most influential one was peak current in so far to have a machining with higher accuracy and quality, its relevant level must be kept at least as much as possible whereas, in this case, this selection will lead to a condition with a smaller material removal rate. Accordance to Grey Relational Analysis, a simultaneous calculation performed on the four responses: wear rate , material removing rate, overcut and Surface roughness and the parametric treatment for an acceptable machining in terms of quality and time, suggested as I = 8A, Ton = 50µs, Toff = 5 µs, V = 40v and P = 0. It should be noted that on the basis of relative degrees of gray as the primary and secondary quantitative index optimization, by selecting this parameter, the overall performance is improved by about 20% .