Response Surface Methodology (RSM) based analysis for tool life optimization in cryogenic CO2 milling of Inconel 718

Abstract

This study presents the tool life optimization of carbide coated ball nose milling inserts using high-speed milling Inconel 718 under cryogenic CO2 environment. A total of 29 experiments were conducted based on Box-Behnken Response Surface Methodology using the 4 factors; cutting speed (Vc: 120-140 m/min), feed rate (Fz: 0.15-0.25 mm/tooth), axial depth of cut (ap: 0.3-0.7 mm), and radial depth of cut (ae: 0.2-0.6 mm) at three levels each. By using ANOVA, it was found that all factors have significant effects on tool life. However, the feed rate shows its highest influence on the tool performance where the tool life can be lengthened by reducing the feed rate values. After that, the relevant influencing parameters on tool life were derived in the form of mathematical model which was then used to predict the response within the predetermined parameters. With an average error of 8.2% between the predicted and actual tool life, it confirms the adequacy of the model in this research. ANOVA also suggests a tool life of 23.40 min could be obtained at optimized parameters of; Vc: 120.06 m/min, Fz: 0.15 mm/tooth, ap: 0.66 mm and ae: 0.53 mm under cryogenic CO2 condition.