Cutting dynamics and process-structure interactions applied to milling

Cutting dynamics should not be restricted only to self-excited chatter vibrations. Transient disturbances are superimposed on stable working conditions and these dynamic components provide useful information on the real behaviour of the whole machining process. Cutting dynamics therefore include the analysis of such signals in the entire frequency range. An introduction to the basic dynamics of milling processes is presented.Milling is a cutting operation during which the periodic sequence of cutting edges generates periodic time signals with discrete force and vibration spectra. A single cutting pulse from the series of successive cuts leads to an aperiodic time function and thus to a continuous spectrum. Since the dynamic behaviour is known at all frequencies a study of the influence of various cutting conditions and the interactions between the cutting process and the machine tool structure is possible. The discrete spectrum of a real cut involving many teeth can be deduced from the corresponding single cutting pulse.A simple cutting force model was assumed in the theoretical analysis in order to give an initial rough idea of the fundamental properties of the milling pulses (frequency content of the spectra, spatial excitation locus and excitation ratio) as a function of the most important parameters (total cutting angle, up and down milling, symmetrical and asymmetrical cut and number of teeth). The computed results were compared with experimentally obtained data.