Optimization and an experimental study on surface roughness of 6061 Aluminum alloy cut by abrasive water jet

Abstract

This study investigates the influence of abrasive water jet cutting (AWJC) parameters on surface roughness (Ra) and kerf morphology of 15 mm-thick AA6061 aluminum alloy. Ra was measured at depths of 2, 6, 10, and 14 mm, increasing from 1.68 µm at the entry to 3.05 µm at the exit, with variability decreasing at greater depths. Kerf morphology revealed the classical tri-zonal structure—smooth, transition, and striation-dominated zones—consistent with the Ra measurements. Taguchi L9 design and ANOVA identified traverse speed as the dominant factor influencing Ra (61.5%), followed by water pressure (34.3%), while stand-off distance (SoD) had only a minor influence (≈1.3%) within the tested range (3–7 mm). A multiple linear regression model (S = 0.145 µm, R² = 97.14%, adjusted R² = 96.29%) accurately predicted Ra trends: higher traverse speed increased Ra by reducing jet–material interaction time, whereas higher water pressure reduced Ra by maintaining jet coherence and extending the smooth cutting zone. At the optimal parameters (P = 3800 bar, V = 50 mm/min, SoD = 3 mm; A3B1C1), the model predicted Ra ≈ 1.84 µm. An initial comparison with the experimental mean of 1.97 µm (Run 7) gave a 6.6% error, while a confirmation test yielded a mean of 1.88 µm, reducing the error to only 2.1%. These results validate both the regression model and the Taguchi-based optimization, confirming that surface finish in AWJC of thick AA6061 is primarily governed by traverse speed and water pressure. The depth-resolved analysis provides practical guidance for optimizing process parameters to enhance surface integrity in aluminum components.