Experimental and Statistical Investigation of Surface Roughness in Turning of AISI 4140 Steel

Abstract

In this study, AISI 4140 tempering steel with 48 HRc hardness was machined on CNC lathe with different cutting parameters and cooling environment. The Taguchi L9 test design was developed based on the three-level cutting speed, feed, chip depth and cooling environment parameters. The average surface roughness (Ra) values were measured in experiments made according to the L9 test design. Chip form occurring during turning is photographed. The Signal/Noise (S/N) ratios of the Taguchi experiment design in the Minitab program have been determined. According to the experimental results, the most significant effect on the Ra from the four factors was found in the hand made by the depth of cut. In ANOVA analysis, it was respectively determined that depth of cut, cutting speed, feed rate and cooling environment affected 95% confidence in Ra value. It has been found that the repeat experiments for the optimum parameters yielded about 90% accuracy compared to the Taguchi estimate.