The influence of feed rate on process damping in milling: Modelling and experiments

The performance of milling operations is limited by the onset of unstable self-excited vibrations known as regenerative chatter. Over the past few decades there has been a great deal of research to help predict and explain regenerative chatter. Consequently, high-speed milling operations are now frequently employed, with judicious choice of spindle speeds and depths of cut so as to avoid chatter whilst maintaining high productivity. However, many materials that are increasingly used in aerospace components are difficult to machine at high spindle speeds because of their thermal properties. Examples include titanium and nickel alloys. For these materials, low-speed machining must be employed, and in this regime the role of regenerative chatter is less clearly understood due to the phenomenon of process damping.

In the present study, a time domain model of process damping is developed. This model is used to explore the relationship between cutting conditions and the amplitude of chatter vibrations. A qualitative agreement is found between experimental behaviour and the numerical model. In particular, the model predicts a strong relationship between the workpiece feed rate (expressed as a feed per tooth), and the acceptable chatter stability defined by the process damping wavelength. Further work is needed to properly calibrate some of the model parameters.