Experimental identification of milling process damping and its application in stability lobe diagrams

Self-excited vibrations represent one of the most unfavorable phenomena in the cutting process because they can lead to the accelerated wear or breakage of the tool, a sudden deterioration in the quality of the machined surface, and an increase in noise and energy consumption. To avoid these negative effects, stability diagrams are used when defining the cutting regimes, which, depending on the main spindle speed and the cutting depth, show the border between the stable and unstable machine tool operation states from the aspect of self-excited vibrations. These diagrams, known as “stability lobe diagrams”, can be defined using mathematical models (analytical or numerical) or through experimental methods. However, when machining at relatively low main spindle revolutions, process damping occurs, which increases the system stability, i.e., enables a greater cutting depth limit. For the stability diagram to be effectively used for predicting the cutting depth limits at low machining speeds, it is necessary to take the effect of process damping into account. This paper introduces an experimental method for the determination of process damping and its integration into the mathematical framework of the Fourier series method, commonly utilized for the construction of stability lobe diagrams.