Experimental Evaluation of EDM Parameters for MO40 Steel Using RSM and Thermal Heat-Flux Analysis

Electrical Discharge Machining (EDM) is a vital manufacturing process for hard materials, particularly alloy steels, extensively utilized in mold making, aerospace, and automotive industries. In this study, the effects of discharge voltage, peak current, pulse-on time, and electrode material (copper vs. graphite) on the Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness of MO40 alloy steel were experimentally investigated. The experiments were designed using the Response Surface Methodology (RSM) with the Box-Behnken design, and regression models and Analysis of Variance (ANOVA) were employed to evaluate the main effects and interactions of the parameters. The results indicate that peak current has the most significant impact on the MRR, while discharge voltage and pulse-on time have the greatest influence on surface roughness. Furthermore, the TWR is primarily governed by the physical properties of the electrode; copper electrodes exhibit higher wear due to their high thermal conductivity. The optimization results revealed that the maximum MRR achieved was 0.010362 g/min (graphite electrode), the minimum TWR was 0.00000167 g/min (copper electrode), and the minimum surface roughness was 0.7695 μm (graphite electrode). Additionally, a thermal model for local heat flux, based on the radial distance from the spark center, was developed, yielding a maximum value of 6.688 MW/m² under conditions of 120 V, 8 A, and 100 μs.