Statistical Investigation into the Effects of Electro-Discharge Machining Parameters on WC/6%Co Composite-Part 1: Modeling through Response Surface Methodology (RSM)

In this two-part research, a unified approach is presented to model and optimize the electro-discharge machining (EDM) parameters on WC/6%Co using response surface methodology (RSM) and desirability function (DF) concept. In the first part, four controllable parameters, viz., discharge current (A), pulse on-time (B), duty cycle (C), and average gap voltage (D) have been selected as the input variables to evaluate the process performance in terms of material removal rate (MRR), tool wear rate (TWR), and arithmetic mean surface roughness (Ra) as the performance characteristics. The modeling phase begins applying face-centered central (FCC) composite design to plan and analyze the experiments in accordance with the RSM. For every response, the significant forms of influential parameters were properly identified conducting a comprehensive analysis of variance (ANOVA) at 1, 5, and 7% level of significance. It has been revealed that all the direct effects of input parameters are extremely momentous affecting both the MRR and TWR. Moreover, the pure quadratic effect of duty cycle (C2), the reciprocal effects of discharge current with pulse on-time (A×B), duty cycle (A×C), and gap voltage (A×D), as well as the interaction amongst the pulse on-time with duty cycle (B×C) were also reached to be important terms affecting the MRR. The TWR measure behaves the same way, however, it exhibits a more nonlinear mathematical form containing the second order effect of discharge current (A2) as an additional important term. On the other hand, for the Ra, the only significant parameters are the main effects of the first two inputs (A and B) plus the interactions of current with pulse on-time (A×B) and with gap voltage (A×D). The results indicate that the suitably proposed step-by-step implemented approach can substantially elucidate the highly multifaceted behavior of the chosen grade WC-Co under different EDM conditions providing a reliable platform to both navigating the operational region and seeking for optimal working circumstances confidently.