Robust Parameter Design of an EDM Process

The paper details a robust parameter design of an electrical discharge machining process. The influence of capacitance, pulse off‐time, pulse on‐time and pulse current on both the average and variability of surface roughness and material removal rate of a titanium alloy was investigated. The analysis revealed that to attain robustness against the impact of noise parameters, no capacitance should be applied. Furthermore, increasing pulse on‐time and its current increased the average of both the surface roughness and material removal rate. Two approaches were suggested to deal with the trade‐off between minimizing the former and maximizing the latter. The study confirmed empirically the inferiority of Taguchi's S/N ratios to a robust design method involving the use of log(s) together with a simple graphical tool for determining the appropriate data transformation called lambda plot. In fact, it was revealed that the employed S/N ratios were driven mainly by the average and involved unaided, unexplained and unjustified transformations. The log(s), on the other hand, provided an independent means of quantifying the variability and, when integrated with lambda plot, rendered not only a simplified analysis but also a better process understanding. The study is the first to report the use of this powerful approach in the context of electrical discharge machining parameter design. Copyright © 2012 John Wiley & Sons, Ltd.