An analytical force model for modulation-assisted turning

Modulation-assisted machining (MAM) superimposes a controlled low-frequency tool oscillation in the feed direction of conventional machining (CM). The process transforms the otherwise continuous cutting into a series of interrupted cutting events, producing discrete chips instead of continuous chips. This paper makes a geometrical analysis of the MAM process in face turning configuration and classifies it into two cutting phases according to the different direction of the instantaneous feed motion: conventional cutting phase and reverse cutting phase. An analytical force model is proposed to determine the instantaneous forces for both cutting phases, which incorporates material properties, tool geometry, cutting conditions and modulation conditions. Several unknown model parameters are identified via an elitist teaching-learning-based optimization (TLBO) algorithm. A series of face turning experiments are carried out with and without modulation, validating the identified parameters and the proposed force model. Finally, the effects of modulation frequency, modulation amplitude and nominal feed rate on the three-dimensional forces are studied and discussed both qualitatively and quantitatively. The analytical force model in this paper can provide a framework for characterizing the effect of process parameters on applications for MAM.