Evaluation of cutting forces and prediction of chatter vibrations in milling

Abstract

The prediction of chatter vibrations between the cutter and workpiece is important as a guidance to the machine tool user for an optimal selection of depth of cut and spindle rotation, resulting in maximum chip removal rate without this undesirable vibration. This can be done by some approaches. In this work, an analytical method is applied in which the time-varying directional dynamic milling forces coefficients are expanded in Fourier series and integrated in the width of cut bound by entry and exit angles. The forces in the contact zone between cutter and workpiece during the cut are evaluated by an algorithm using a mathematical model derived from several experimental tests with a dynamometer located between the workpiece and machine table. The algorithm results depend of the physical properties of the workpiece material and the cutter geometry. The modal parameters of the machine-workpiece-tool system like natural frequencies, damping and residues must also be identified experimentally. At this point, it is possible to plot the stability lobes to this dynamic system. These curves relates the spindle speed with axial depth of cut, separating stable and unstable areas, allowing the selection of cutting parameters resulting maximum productivity, with acceptable surface roughness and absence of chatter vibrations. Experimental face milling tests were performed in a knee-type machine, using a five inserts cutter. The results showed perfect agreement between chatter prediction and experimental tests

Vibrational Impact on Milled Surface Irregularities

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A new damping modelling approach and its application in thin wall machining

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Cutting parameters and vibrations analysis of magnetic bearing spindle in milling process

“…A research performed by Zatarain et al (2006) showed that mill helix angle could play an important role in instability due to repetitive impact driven chatter. In order to predict the occurrence of chatter vibrations, Lacerda and Lima (2004) applied an analytical method in which the time-varying directional dynamic milling forces coefficients were expanded in Fourier series and integrated along width of the cut bound by entry and exit angles. Wan et al (2010) proposed a unified method for predicting stability lobes of the milling process with multiple delays.…”