ANALYSIS OF EDM PROCESS PARAMETERS WITH TOOL ROTATION

Abstract

This study comprehensively investigated the impact of Electrical Discharge Machining (EDM) parameters—including peak current, grit size, tool rotation speed, and electrode material (graphite and copper)—on the machining performance of EN31 and AISI D3 steels. The Material Removal Rate (MRR) increased with peak current for both electrodes, with graphite consistently achieving higher MRR, lower surface roughness (SR), and reduced tool wear rate (TWR) across most conditions. Surface finish improved significantly with increasing grit size when using graphite electrodes, whereas copper electrodes exhibited deteriorating surface roughness with higher peak currents. Tool wear behaviour varied inversely with current and electrode type; graphite showed 139.54% higher wear than copper at 12 A, but copper wear was 571.1% higher than graphite at 8 A. The minimum TWR was recorded at 15.28 mg/min for graphite at 1800 rpm, outperforming copper’s 22.46 mg/min at 1200 rpm. Graphite electrodes demonstrated superior performance by providing greater MRR and lower SR for both steels, although copper outperformed graphite at a peak current of 12 A for EN31. Surface roughness reductions of 20.83% and 9.87% were observed with graphite and copper electrodes, respectively, during EN31 machining, with tool rotational EDM further improving surface morphology and uniformity, as confirmed by FESEM analysis. Residual stress evaluations revealed increases in tensile and compressive stresses correlated with higher thermal contraction rates and pulse durations, with copper showing 9.81% higher σₓ in D3 steel, while graphite induced a 40% higher shear stress (τₓᵧ). Statistical modelling validated the significant influence of peak current, grit size, and tool rotation on machining responses. Optimal parameters for EN31 and D3 steels were identified, achieving maximum MRRs of 594.6 mg/min and 570.3 mg/min, minimum surface roughness values of 9.12 μm and 9.75 μm, and low tool wear rates. Elemental analysis indicated greater carbon deposition with graphite electrodes (18.33%) compared to copper (9.27%), which affected surface integrity.