Effect of Machining Conditions for Enhanced Surface Integrity and Cutting Temperature in Trimming Hybrid Fiber-Reinforced Polymer Composites

This study aims to evaluate how cutting parameters influence surface quality and cutting temperature during the trimming of Hybrid Fiber Reinforced Polymer (HFRP) used in aerospace components. Although HFRP is increasingly adopted in aircraft structures, it remains difficult to machine because trimming can trigger delamination, matrix degradation, and non-uniform heat generation across the laminate. To address this, a Taguchi L9 Orthogonal Array was applied to systematically examine the effects of spindle speed and feed per tooth on two key outcomes: surface roughness (Ra) and maximum cutting temperature (Tmax). Trimming experiments were performed on a Roland MDX540 CNC router, and surface integrity was assessed using optical microscopy, thermal imaging, and ANOVA. Two parameter settings emerged as optimal, depending on the targeted response. The lowest surface roughness was achieved at 7518 RPM with 0.10 mm per tooth (Ra = 2.44 µm), whereas the lowest cutting temperature occurred at 5012 RPM with 0.15 mm per tooth (Tmax = 110.2 °C). Since surface integrity is the primary quality requirement for aerospace trimming, the condition of 7518 RPM / 0.10 mm per tooth was selected as the most practical optimum. This setting provides a noticeably improved surface finish while keeping the cutting temperature at a moderate level (approximately 115 °C), which remains safely below the threshold for polymer matrix degradation. ANOVA results further indicate that feed per tooth is the dominant factor governing surface roughness, while spindle speed has the strongest influence on cutting temperature. Overall, the findings support a dual-objective optimization approach that balances mechanical surface integrity and thermal control, providing practical parameter guidance for consistent, high-quality trimming of HFRP aerospace parts.