Study of the finish turning process based on the Parameter Space Investigation method

Abstract

This paper describes a future-proof Design of Experiment (DoE) method, namely the Parameter Space Investigation (PSI) method. This method reduces the number of test points compared to other DoE approaches, such as single factor design, full factorial design, fractional factorial design, and central composite design, and the number of test points is sufficient for statistical analysis. It allows an efficient analysis of process phenomena, among others, some cutting effects and surface texture forming. It has been shown that in the space of cutting parameters studied, changes in the chip thickness ratio Kh have extreme points, which can be caused by vibration or the build-up-edge formation, and different types of chip shapes are observed. Changes in Kh correlate with chip shapes. In the ranges of depth of cut ap = 0.2 − 1.2 mm and feeds f = 0.05 − 0.4 mm/rev, depending on cooling conditions, the changes in cutting force reach up to 80%. For cutting speeds vc = 50 − 200 m/min and feed rates f = 0.03 − 0.17 mm/rev, the relationships Ra = f(vc,f) are complicated, and the PSI method ensures finding minimum Ra values and areas of physicochemical phenomena. Optimizing the turning conditions over a wide range, at the first stage, the minimum Sa values were obtained in the area of vc = 150 − 300 m/min and f = 0.05 − 0.22 mm/rev, and at the second stage in the areas of vc > 240 m/min and f = 0.03 − 0.07 mm/rev and vc = 100 − 120 m/min and f = 0.01 − 0.13 mm/rev. In addition, the shaping of the machined surface was affected by vc, f, and their interaction. Compared to the first optimization stage, the second stage provided Sa values almost 2 times smaller. It has been proven that the PSI method is effective and can be widely used in various areas of multivariate experimental research and optimization of cutting processes.