Optimization of Correlated Responses of EDM Process

Electrical discharge machining (EDM) process has several important performance measures (responses), some of which are correlated. For example, material removal rate (MRR) and electrode wear rate (EWR) are highly correlated. No reported research work on EDM process has taken into consideration the possible correlation between the response variables while determining the optimal process conditions. Thus, the results achieved by the past researchers are often suboptimal. In the recent past, a few multiresponse optimization methods have been proposed that make use of the principal component analysis (PCA) to take into account the possible correlation between the responses. So, ideally, these methods should be more effective for optimizing the EDM process. However, the relative optimization performances of these methods are unknown and therefore, the process engineers may face the difficulty in selecting the most appropriate method for optimizing an EDM process. In this article, two sets of past experimental data on EDM processes are analyzed using four PCA-based optimization methods. The optimization performances of these methods are compared with the results achieved by the past researchers, considering expected total signal-to-noise (S/N) ratio as the utility measure. It is found that the PCA-based approaches, in general, lead to better optimization performance and among the four PCA-based approaches, PCA-based proportion of quality loss reduction (PQLR) method results in the best optimization performance. So the PCA-based PQLR method can be applied for optimizing multiple responses of EDM process.