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

Abstract

Electric Discharge Machining (EDM) is commonly used to machine hard materials. However, making small and precise features with EDM requires careful control of process parameters. This study presents an improved method to drill micro-holes in 1 mm-thick stainless steel (SS 316L) using a 0.6 mm copper electrode. 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. Experimental validation showed strong concordance with the outcomes predicted by the RSM. SEM analysis revealed negligible recast layer and consistent taper geometry, affirming the reliability of the optimized conditions for high-precision micromachining.