Optimisation of CNC Turning Process Parameters for Surface Roughness and Material Removal Rate of EN8 Medium Carbon Steel Using Taguchi L9 Orthogonal Array and Analysis of Variance

Abstract

CNC turning is one of the most widely used machining operations in manufacturing industries, producing cylindrical and contoured components across automotive, agricultural machinery, pump, and general engineering sectors. The quality of the turned surface, quantified as surface roughness Ra, determines the functional performance of the machined component — governing friction, wear, fatigue life, and sealing effectiveness — while the material removal rate (MRR) determines machining productivity and cost per component. These two output responses are inherently in conflict: parameter settings that maximise MRR (high feed rate, deep depth of cut) tend to worsen surface roughness, while settings that minimise Ra (low feed rate) reduce productivity. Systematic optimisation of the three principal CNC turning parameters — cutting speed, feed rate, and depth of cut — is therefore essential for balancing quality and productivity. This paper presents a Taguchi L9 orthogonal array-based experimental investigation of CNC turning of EN8 medium carbon steel (080M40, hardness 180–207 HB) using a CVD-coated carbide insert under dry cutting conditions. Three factors at three levels each are studied: cutting speed (80, 120, 200 m/min), feed rate (0.10, 0.20, 0.30 mm/rev), and depth of cut (0.5, 1.0, 1.5 mm). Signal-to-Noise (S/N) ratio analysis with smaller-the-better criterion for Ra and larger-the-better for MRR, ANOVA, and main effects plots are used to identify optimal settings and rank parameter contributions. ANOVA identifies cutting speed as the dominant factor for Ra (46.8% contribution) followed by feed rate (38.4%), while depth of cut has negligible influence (2.7%). The optimal parameters for minimum Ra are: Vc = 200 m/min, f = 0.10 mm/rev, d = 0.5 mm, achieving Ra = 1.42 µm in confirmation experiments — a 72.3% improvement over the worst-case condition.

Cite as:

Akshay V. Patil. (2026). Optimisation of CNC Turning Process Parameters for Surface Roughness and Material Removal Rate of EN8 Medium Carbon Steel Using Taguchi L9 Orthogonal Array and Analysis of Variance. Research and Reviews on Experimental and Applied Mechanics, 9(2), 38–46. https://doi.org/10.5281/zenodo.21904173