Investigation of Electrode Wear, Machining Performance, and Surface Characteristics in Rotary EDM Using a Multi-Material Composite Electrode

Electrode materials and discharge parameters play critical roles in determining the machining efficiency and precision of electrical discharge machining (EDM). Conventional EDM generally employs a single electrode material, which may limit discharge performance and the surface characteristics of the machined workpiece. This study developed a multi-material composite electrode (MMCE) using materials with different melting points, electrical conductivities, and thermal conductivities. The MMCE was designed to develop a stepped end-face profile through differential wear of its constituent materials during rotating EDM. This profile, combined with electrode rotation, may facilitate dielectric circulation and debris evacuation. The MMCE consisted of three one-third sector-shaped cylindrical segments made of copper (Cu), aluminum alloy (Al6061), and mold steel (SKD11), respectively, forming a cylindrical electrode with a diameter of 20 mm. Pulse duration, peak current, and duty factor were selected as experimental parameters. The material removal volume (MRV), electrode wear volume (EWV), and machining depth were evaluated and compared with those obtained using conventional single-material cylindrical electrodes made of Cu, Al6061 and SKD11. The experimental results revealed differential wear among the MMCE segments, resulting in a stepped electrode end-face profile. This profile, combined with electrode rotation, may facilitate dielectric circulation and debris evacuation, potentially contributing to improved EDM process stability. At a duty factor of 0.5, the MMCE achieved an MRV approximately 98% of that obtained with the Cu electrode, while its EWV was approximately three times higher. Furthermore, energy-dispersive X-ray spectroscopy detected Cu and Al on the machined surface, supporting the transfer of electrode-derived elements to the workpiece and indicating the potential of the MMCE to modify surface composition during rotating EDM.