Development of a mechanistic cutting force model for wavy-edge bull-nose helical end-milling of inconel 718 under emulsion cooling strategy

Abstract

This paper presents the results of the development of a mechanistic cutting force model to predict cutting forces in high-speed end-milling of Inconel 718 using a wavy-edge, bull-nose, helical endmill (which hereafter will be abbreviated as WEBNHE). The model incorporates the effects of emulsion cooling strategy into the mechanistic cutting force model through the experimental determination of six specific cutting force and edge force coefficients. The cutting force is predicted as three components (Fx, Fy, and Fz) and the resultant cutting force FR. The mechanistic cutting force model depends on a mathematical model to represent the geometry of this endmill, which is also developed in this research. The mechanistic model also depends on three cutting force coefficients in the tangential, radial, and axial directions (ktc, krc, kac, respectively), and on three edge force coefficients (kte, kre, kae), also in the tangential, radial, and axial directions. These coefficients are determined experimentally in a separate work in which “emulsion” was applied as the cooling strategy. MATLAB codes were developed and used to simulate the developed mathematical and mechanistic cutting force models. Finally, to validate the mechanistic cutting force model, machining experiments were conducted and real cutting force components were measured and compared with the predicted cutting force components. The predicted values agree fairly well with the experimentally measured values in both magnitude and shape. The percentage of the prediction error for the highest peak force magnitudes at 93 rpm were 11.38%, –0.46%, and 11% for the Fx, Fy, and Fz components respectively, while the percentage prediction error for the lowest cutting force magnitudes are 15.25%, 17.84%, and 10% for Fx, Fy, and Fz components respectively. The developed mechanistic cutting force model can be used to investigate the effect of tool geometry and machining parameters on cutting forces, machining power, machine tool vibration, and to simulate the end-milling process to improve machinability and productivity, and also to understand more fully the end-milling process using WEBNHE.