Modeling Dynamic Stability and Cutting Forces in Micro Milling of Ti6Al4V Using Intermittent Oblique Cutting Finite Element Method Simulation-Based Force Coefficients

Abstract

Tool breakage is a significant issue in micro milling owing to the less stiffness of the micro tool. To cope up with such limitation, precise predictions of dynamic stability, and cutting force have the utmost importance to monitor and optimize the process. In this article, dynamic stability and cutting force are predicted precisely for micro milling of Ti6Al4V by obtaining force coefficients from a novel 3D intermittent oblique cutting finite element method (FEM) simulation considering the influence of tool run out. First, the stability model is modified by incorporating the appropriate values of limiting angles obtained analytically accounting the trajectories of the flutes due to tool run out. This stability model is utilized to select chatter-free parametric combinations for micro milling tests. Next, an improved cutting force model is developed by incorporating the force coefficients obtained from oblique cutting simulation in the mechanistic model and differentiating the whole machining region into three distinct region considering size effect. The force model also considers the effect of increased edge radius of the worn tool, run out, elastic recovery, ploughing, minimum undeformed chip thickness (MUCT), and limiting angles, cumulatively. The proposed dynamic stability and cutting force models based on the oblique cutting simulation show their adequacy by predicting the stability limit and cutting force more precisely, respectively, as compared to those obtained by orthogonal cutting simulation. Besides, the proposed force model for the worn tool is found to be viable as it is closer to the experimental forces, whereas force model without the incorporation of tool wear underestimated the experimental forces.