Högskolan i Skövde

In many industries, indexable insert drills are used to cost effectively produce short holes. However, common problems such as chatter vibrations, premature tool wear and generation of long curly chips that cause poor chip evacuation make optimization of the drilling process challenging and time-consuming. Therefore, robust predictive models of indexable drilling processes are desirable to support the development towards improved tool designs, enhanced cutting processes and increased productivity. This paper presents 3D finite element simulations of indexable drilling of AISI4140 workpieces. The Coupled Eulerian–Lagrangian framework is employed, and the focus is to predict the drilling torque, thrust force, temperature distributions and chip geometries. To reduce the computational effort, the cutting process is modelled separately for the peripheral and the central inserts. The total thrust force and torque are predicted by superposing the predicted result for each insert. Experiments and simulations are conducted at a constant rotational velocity of 2400 rpm and feed rates of 0.13, 0.16 and 0.18 mm/rev. While the predicted torques are in excellent agreement, the thrust forces showed discrepancies of 12 - 20% to the experimental measured data. Effects of the friction modelling on the predicted torque and thrust force are outlined, and possible reasons for the thrust force discrepancies are discussed in the paper. Additionally, the simulations indicate that the tool, chip and the local workpiece temperature distributions are virtually unaffected by the feed rate.