Single and multi-objective optimization for cutting force and surface roughness in peripheral milling of Ti6Al4V using fixed and variable helix angle tools

Abstract

Ti6Al4V titanium (Ti) alloy is a frequently used engineering material in industrial applications due to its superior properties. In this work, single-objective and multi-objective methods were used to optimize control factors (cutting speed, feed rate, and cutting tool helix angle) for minimal cutting force (Fc) and surface roughness (Ra) in peripheral milling of Ti6Al4V. Machinability experiments were performed using carbide end mill cutting tools with fixed and variable helix angles. Following the machinability tests performed using the L18 orthogonal array, the Taguchi technique was used as a single-objective optimization for each of the cutting forces and surface roughness. The Entropy-weighted TOPSIS approach was used in the second step to provide the optimum levels of the control factor, which minimizes both cutting force and surface roughness. The effects of control factors and interactions on thrust force and surface roughness were determined by Analysis of Variance (ANOVA) and contour plots. As a result of this study, it was determined that the helix angle of the cutting tool (84.91 % contribution) was the most effective parameter on the cutting force and the feed rate (22.71 % contribution) on the surface roughness. The cutting force and surface roughness values decreased in peripheral milling at high cutting speed, whereas the cutting forces increased, and the surface quality of the workpiece deteriorated in machining at high feed rates. The helix angle of the cutting tool has a favorable influence on the cutting force and surface roughness when milling with fixed helix tools. Cutting forces are minimized, and workpiece surface quality is improved using cutting tools with a larger helix angle. Variable helix tools with a large helix angle performed best in cutting force and surface roughness. Variable helix end mills with large helix angle (HA = 35°/38°), high cutting speed (Vc:108 m/min), and a low feed rate (f:0.04 mm/tooth) should be used in peripheral milling of Ti6Al4V Ti alloy to achieve both minimum cutting force and best surface quality. The mean cutting force and surface roughness values were obtained as 628.69 N and 0.363 μm, respectively, in the peripheral milling process performed at different levels of control factors. The cutting force was reduced to 227.52 N (34.71 % improvement) and the surface roughness value to 0.237 μm (276.32 % improvement) using the Entropy-weighted TOPSIS multi-objective optimization approach.