Optimization of laser cutting parameters for enhanced kerf surface quality of thick Al6061-T6 aluminum alloy

This study investigates the influence of key fiber laser cutting parameters, laser power, cutting speed, nozzle stand-off distance, and focus position, on the surface roughness of thick Al6061-T6 alloy, focusing on average roughness (R_a), areal roughness (S_a), and maximum peak-to-valley height (S_z). Using a Taguchi L27 orthogonal design and optical laser microscopy at various depths, surface quality was analyzed through main effects plots and ANOVA. Results identified nozzle stand-off distance as the most critical factor for minimizing R_a and S_a, with the smoothest surfaces achieved at a 1.0 mm, while focus position (–1.5 mm) provided secondary improvements in energy concentration. In contrast, S_z was mainly influenced by laser power and cutting speed, with greater values of both lowering peak roughness. The ideal parameter set 2750 W, 600–750 mm min⁻¹, 1.0 mm nozzle standoff distance, and −1.5 mm focus, provided exceptional surface integrity, emphasizing the importance of balancing thermal input with accurate nozzle and focus settings for high-quality laser cutting of aluminum. The results indicate that although controlling thermal parameters such as laser power and cutting speed is essential for minimizing peak roughness features, achieving superior surface integrity in aluminum laser cutting also requires precise tuning of the nozzle stand-off distance and beam focus.