Process optimization and characterization of micro-drilling in PMMA-Epoxy/MWCNT/Fe ₃ O ₄ hybrid nanocomposites

The present study investigates the micro-drilling performance of (Polymethyl Methacrylate-epoxy) PMMA-epoxy/Multiwalled Carbon Nanotube (MWCNT)/Magnetite (Fe ₃ O ₄ ) hybrid nanocomposites through experimental characterization and process optimization. The hybrid nanocomposite was prepared using MWCNTs and Fe ₃ O ₄ nanoparticles, and then characterized by scanning electron microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and UV-Visible spectroscopy. A 27-run full-factorial experimental design was employed to investigate the effects of tool diameter (0.3–0.5 mm), spindle speed (800–1200 rpm), and feed rate (1–3 mm/min) on Material Removal Rate (MRR). Based on the constant drilling depth and feed-controlled machining condition, the theoretical MRR relationship was found to depend primarily on tool diameter and feed rate; therefore, the DOE and analysis of variance analysis (ANOVA) considered tool diameter and feed rate as the principal MRR variables. The quadratic model was statistically significant ( p < .0001) and demonstrated excellent predictive capability with R ² = 0.9985, adjusted R ² = 0.9981, and predicted R ² = 0.9976. Tool diameter, feed rate, and their interaction were highly significant contributors to MRR. The maximum experimentally measured MRR of 0.009345 mm ³ /s was obtained using a 0.5 mm drill and 3 mm/min feed rate at 1000 rpm; however, the spindle speed is reported as the experimental condition associated with the maximum measured response rather than as an independently optimized MRR parameter. Contour and response surface analyses further confirmed the positive and interactive effects of tool diameter and feed rate on MRR. SEM examination of the drilled specimen provided morphological evidence of the 27 experimental holes, while selected magnified images illustrated representative hole-edge morphology, burr formation, and debris characteristics across the three drill diameters. EDS, FTIR, and UV-Visible analyses confirmed the incorporation and characteristic structural/optical features of the hybrid nanocomposite. The findings establish tool diameter and feed rate as the principal parameters for controlling MRR during micro-drilling of the PMMA-epoxy/MWCNT/Fe ₃ O ₄ hybrid nanocomposite and provide a statistically supported basis for process optimization.