Investigation of the effect of micromachining parameters on the accuracy of micro-holes drilled by electric discharge machine

This study presents an optimized approach for producing precise micro-holes in 1 mm-thick stainless steel (SS 316L) using Electric Discharge Machining (EDM) with a 0.6 mm copper electrode. While EDM is well-known for machining hard materials, its effective application in micro-feature generation demands thorough investigation of process parameters. The key novelty of this work lies in the integration of Response Surface Methodology (RSM) and Central Composite Design (CCD) for multi-response optimization, coupled with validation through experimental testing and microstructural analysis via Scanning Electron Microscopy (SEM). The influence of peak current (2–6 A), pulse-on time (10–40 μs), and pulse-off time (4–6 μs) was evaluated across response factors such as micro-hardness, edge deviation, overcut, material removal rate (MRR), taper angle, and tool wear rate (TWR). The optimal parameter combination is 2 A current, 16.577 μs pulse-on time, and 6 μs pulse-off time, yielded a high desirability score of 8.33, with corresponding results of 283.98 HV microhardness, 7.625 μm (entry) and 5.321 μm (exit) edge deviation, −43.691 μm (entry) and −166.271 μm (exit) overcut, 3.538 g/min MRR, taper angle of 1.877°, and 1.811 g/min TWR. Validation experiments confirmed close alignment with RSM predictions. SEM analysis revealed negligible recast layer and consistent taper geometry, affirming the reliability of the optimized conditions for high-precision micromachining.