An investigation on the cutting force of milling Inconel 718

¹ Department of Mechanical Engineering, National Chung-Hsing University, Taiwan
² Intelligent Machinery Center, Industrial Technology Research Institute, Taiwan

^a Corresponding author: jctsai@mail.nchu.edu.tw

Abstract

Inconel alloy has been widely used in industry but is difficult to machine due to its rapid change in cutting force during machining. This paper investigated the cutting force for milling Inconel 718 as conventional force model is unable to handle the above situation. Theorectical force model is first reviewed and two-phase experiments of slot milling based on dry cutting are designed to measure the cutting force and the specific cutting force. Experiments in phase I are designed based on Taguchi method with spindle speed, feedrate per cutting edge and depth of cut as experimental parameters. The results showed that the first two parameters play more important roles in the cutting force. A phase II exhaust experiments is designed with spindle speed set from 400 to 800 rpm while the feedrate per cutting edge is set from 0.04 to 0.08 mm/tooth. The results are concluded as the following. (i) There exists a strong size effect in milling Inconel 718 as the cutting force changed with the chip thickness. Specific cutting force is larger at small thickness of cut and become smaller when the thickness increases. (ii) A 2^nd order non-linear cutting force model, which takes spindle speed N and feedrate f_z into account, for milling Inconel 718 is derived from the measured data and represented as F_t(N, f_z )= (13910 -3.1N - 109900fz - 0.0028N2 +23.9Nf_z+434500f_z²) xa_pxh. The derived force model compensates the inaccuracy of conventional force model.