OPTIMIZING SURFACE ROUGHNESS IN DRY-TURNING AISI 1029 STEEL WITH CARBIDE INSERT TOOLS ON THE LATHE MACHINE USING TAGUCHI'S METHOD

Abstract

The AISI 1029 carbon steel type is frequently machined by turning operations to produce bolts, nuts, washers, threaded rods, studs, and other fasteners for various engineering applications. The paper demonstrates the use of the Taguchi optimization method in determining the optimum surface finish as a special quality requirement in the turning of the steel on the lathe machine. Taguchi’s L-9 Latin-squares orthogonal arrays were designed with cutting speeds of 125, 250, and 500 m/min; feed rates of 0.1, 0.2, and 0.3 mm/rev; and cut depths of 0.5, 1, and 1.5 mm. Dry-turning experiments were conducted on the XL9 400 lathe machine with a 79.6-mm-diameter and 200-mm-length solid rod of the steel under each array of cutting conditions. The produced surface roughness responses from the turning operations were measured and analyzed by generated signal-to noise ratios, main effect plots, contour plots, surface plots, and analysis of variance on the basis of Taguchi’s concept of the smaller the better using the Minitab-17 software. The analyses showed that the 500-mm/min cutting speed, 0.1-mm/rev feed rate, and 1.5-mm depth of cut array produced optimal surface roughness in the turning operations. Analysis of variance at 95% confidence level showed that feed rate variation had the greatest contribution of 61.78% to surface roughness, followed by depth of cut with 26.22%, and cutting speed with 8.865%. The confirmation test at the optimal turning conditions indicated 2.20-µm optimal surface roughness with only 2.3% error against the 2.15-µm value obtained with the Minitab-17-generated regression equation