Chatter suppression in milling with anisotropic tools

Abstract

Chatter vibration in milling often results in poor surface finish and rapid tool wear, consequently limiting productivity. Thus, chatter suppression is one of the most important themes in industry. Self-excited chatter vibration in milling is generally caused by two kinds of mechanisms, i.e., regeneration and mode-coupling, and both mechanisms should be handled simultaneously to suppress the chatter vibration. Since the mode-coupling can be restricted by separating the natural frequencies of the vibration modes, it has been considered that use of an anisotropic rotating tool is effective on suppressing the chatter vibration in milling. However, the practical effects of the several parameters have not been revealed because it was difficult to predict the chatter stability accurately. On the other hand, the accurate analytical model of the milling process with the anisotropic rotating tool have been developed and verified experimentally by the authors. In order to reveal the practical chatter suppression effect of the anisotropic rotation tool, several cutting conditions, i.e., the immersion angle, the spindle speed and the number of flutes, on the chatter stability are investigated with the developed analytical model in the present study. By comparing the analytical results, it is confirmed that the mode-coupling is restricted and the stability limit in the axial depth of cut increases especially within the low spindle speed range by using the anisotropic rotating tool. The chatter suppression effect also depends on the radial depth of cut considerably. The relationships between the tool conditions, such as the difference of the natural frequencies and flute's angular position, and the chatter suppression effect are also investigated, and it is revealed that both affect the chatter stability significantly.