Chatter Stability Characterization of a Plastic End-Milling CNC Machine

Abstract

The desire to carry out this work arose from an observation during a practical work on a typical plastic end milling CNC machine. It was noticed that under certain conditions of cutting, operation of the machine became noisy with increasing depth of cut and eventual perforation of workpiece therefore the basic aim is to generate stability characterization of the machine in the form of a chart on the plane of cutting parameters on which stable operation is demarcated from the unstable operation . In modelling this machine, a slot creating mode of operation is used since the machine is mainly used for creating logos which are basically collection of slots. The significance of the resulting stability chart lies in the result that the cause of the aforementioned noisy operation is due to unstable parameter combination. For example a laboratory operation at spindle speed of 1500rpm and depth of cut of 1.5mm was noisy while that at spindle speed of 1500rpm and depth of cut of 1mm was serene. The stability chart generated for the system thus shows close agreement with both practice and theory. A unique impact this work will have on the reading community will be in the area of validity of the resulting stability chart on the basis of MATLAB dde23 numerical simulation. The parameters of the end milling process are; tool mass tool natural frequency  damping factor  and workpiece cutting coefficient .

Keywords: chatter, time history, Fargue approximation, Floquet theory, bifurcation