Performance evaluation in die-sinking EDM of polygonal micro cavities over EN-24 alloy steel using cylindrical electrode and polygon cycle approach

The integration of advanced Electrical Discharge Machining (EDM) technology, incorporating short and electronically pulsed discharges with precise circular electrode movements, has enabled the production of intricate 3D microstructures and cavities. This paper aims to investigate the machining performance of polygonal cavities—triangular, square, pentagon, and hexagon—fabricated on steel samples using a 400 µm cylindrical copper electrode within the polygon cycle approach of EDM. Experimental investigations were conducted to assess shape error, tool wear rate, recast layer formation, and elemental characterization. Various discharge patterns and side discharges were examined to understand their effects on spark gap uniformity, tool deflection, and discharge stability. The results revealed non-uniform spark gaps, tool deflection, and corner rounding due to varying discharge patterns and side discharges. Tool wear rate was found to be directly related to polygon complexity, with higher-order polygons leading to increased wear due to extended machining durations and heat accumulation. The maximum tool wear of 7.69 × 10⁴ µm³/s occurred in case of hexagonal cavities while in case of triangular cavities, the tool wear rate was minimum having value of 5.77 × 10⁴ µm³/s. Scanning Electron Microscopy (SEM) examinations showed the presence of recast layers and micro-cracks, particularly in cavities with higher shape complexities. Energy Dispersive X-ray Spectroscopy (EDS) analysis identified copper deposition, local material evaporation, and foreign element accumulation on the cavity surfaces. This study provides insights into the machining performance of polygonal cavities in EDM processes. The findings underscore the influence of discharge patterns, polygon complexity, and material interactions on tool wear, surface quality, and microstructure integrity. Understanding these factors can inform optimization strategies for EDM processes, leading to enhanced precision and efficiency in microstructure fabrication.