Surface Roughness Investigation of Industrial Robot-Based Milling for UHMWPE: A Parametric Study

Abstract

This study investigates the surface quality achievable in robotic milling of Ultra-High Molecular Weight Polyethylene (UHMWPE) components using a KUKA KR120 R2700 six-axis industrial robot equipped with a high-speed spindle. While conventional CNC milling of UHMWPE has been extensively studied, the application of industrial robots for this biomedical thermoplastic remains underexplored despite offering superior flexibility and lower capital costs. A parametric investigation was conducted on spindle speed (6500, 12500, 18500 rpm) and feed rates (180, 900, 1620 mm/min) at three levels with a constant depth of cut (2 mm). The surface quality was assessed in terms of arithmetic average roughness (Ra), root mean square roughness (Rq), and maximum peak-to-valley height (Rz), retrieved and measured through contact profilometry, with three measurements for each condition. Findings indicate a range of surface roughness of Ra = 1.29-3.78 µm for the entire range of parameters, with 1.29 µm Ra roughness at 18500 rpm and 1620 mm/min. The two-way interaction effects showed that all main effects and their interaction were significant (p = 0.0102.) This indicates that for the required optimal range of surface finishes all factors must be selected in a synergistic manner. The predictive models showed good agreement with experimental results (R² = 0.8668), indicating satisfactory predictive capability.  These findings suggest that robotic systems have the potential to be applied as a flexible alternative to CNC machining in suitable applications.  Further investigation is required to evaluate tool wear, material removal rate, and dimensional accuracy for a comprehensive assessment of robotic milling performance.