Enhancing the machinability of recycled polypropylene composites reinforced with waste cotton and pine sawdust through milling parameters optimization

This study investigates the milling behavior of wood-plastic composites (WPCs) made from recycled polypropylene (RPP) reinforced with waste cotton fabric and pine sawdust. The effects of spindle speed (600 rpm, 400 rpm, 200 rpm), feed rate (0.2 mm/rev, 0.4 mm/rev, 0.6 mm/rev), and depth of cut (2.5 mm, 3.0 mm, 3.5 mm) on key response variables—material removal rate (MRR), surface roughness (Ra), machining forces (Fm), and delamination factor (Fd)—were analyzed. ANOVA and Signal-to-Noise Ratio methods were used to evaluate the significance of the parameters, while multi-response optimization was conducted using the Surface Response Optimization Technique. The results showed that spindle speed significantly influenced delamination and surface roughness, while feed rate and depth of cut primarily affected MRR and machining forces. The optimal machining parameters—600 rpm spindle speed, 0.2 mm/rev feed rate, and 3.5 mm depth of cut—achieved an MRR of 23.45 mm 3 /min, Ra of 0.13 µm, Fm of 13.66 N, and Fd of 1.08. The findings underscore the importance of parameter optimization for enhancing machining efficiency and surface quality while demonstrating the potential of these WPCs as sustainable and eco-friendly materials for various applications, particularly in the construction industry.