Characteristics of a reasonably well-adjusted NC servo are given as measured as well as modeled. A model of an A/C loop is added and investigated for stability and for a transient in meeting a sudden increase of depth of cut. Both the classical approach and a numerical simulation (state-space approach) are used. The important effect on stability is shown of a time delay between table velocity change and cutting force change, which is due to the interval between the action of individual cutter teeth. The beneficial effect of a rate feedback on stability is demonstrated.
