Effect of machining parameters on average surface roughness during computer numerical controlled dry milling of high strength AISI 420 martensitic stainless steel

This study focuses on developing an empirical model for average surface roughness during computer numerical controlled (CNC) dry milling of AISI 420 martensitic stainless steel, utilizing response surface methodology (RSM). Experiments were designed with three levels of axial depth of cut, feed rate, and spindle speed to quantify their impact on surface roughness. The RSM-Box-Behnken design was employed to construct the empirical model. Model adequacy was validated through residual analysis and analysis of variance (ANOVA). Analysis of the main effects and interaction effects revealed that the primary influences on average surface roughness were the feed rate, spindle speed, and axial depth of cut, while interaction effects were less significant. Optimal cutting conditions were determined to be a spindle speed of 1500 rpm, a feed rate of 30 mm min⁻¹, and an axial depth of cut of 0.3 mm. The model’s validity was further confirmed through additional validation tests.