Optimization of Small-Hole Drilling Parameters in Electrical Discharge Machining Using Grey Relational Analysis
Received: 28 December 2025 | Revised: 31 January 2026 | Accepted: 8 February 2026 | Online: 2 April 2026
Corresponding author: Kamonpong Jamkamon
Abstract
This study presents an optimization technique for the machining conditions of the small-hole Electrical Discharge Machining (EDM) drilling process. Performance characteristics, such as the Material Removal Rate (MRR) and Electrode Wear Ratio (EWR), were evaluated using Grey Relational Analysis (GRA). A One-Factor-At-a-Time (OFAT) experimental design was employed for testing on SKD61 tool steel, with a brass tube tool electrode of 1 mm outer diameter . The control machining conditions consisted of discharge current, pulse-on time, and pulse-off time. Multiresponse optimization was identified with GRA at a discharge current of 25.5 A, a pulse-on time of 70 µs, and a pulse-off time of 10 µs. The Grey Relational Grade (GRG) improved by approximately 23.79%. The mean MRR and EWR were 5.3484 mm³/min and 2.3139 mm³/min with prediction errors of 6.51% and 7.55%, respectively. Scanning Electron Microscopy (SEM) revealed that electrode wear mainly occurred at the corners and end face of the tubular electrode, resulting in a tapered tool tip and, correspondingly, a tapered drilled hole. The findings suggest that applying optimization parameters using OFAT is feasible with the GRA. In addition, the latter constitutes a robust methodology for multiresponse optimization. The study did not employ any specialized commercial software, demonstrating the utility of GRA in a wide range of manufacturing operations.
Keywords:
EDM small-hole drilling, SKD61, MRR, EWR, grey relational analysisDownloads
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