Cutting force prediction and analytical solution of regenerative chatter stability for helical milling operation

As a new type, highly efficient hole-making technique, helical milling is widely used to generate holes on composites and composite-metal compounds in the aircraft industry. The accurate prediction of cutting forces and chatter stability are essential for achieving a highly efficient and chatter-free helical milling process by cutting condition optimization. On the basis of a quantitative description of cutting zones corresponding to helical milling operation, a novel dynamic cutting force model is proposed for helical milling in this paper, in which the cutting mechanism and the cutting force contribution on both the peripheral and the front cutting edges are taken into consideration simultaneously. An analytical stability prediction method is also proposed to obtain a novel stability lobe diagram represented by the ratio of the axial to the tangential feed per tooth with regard to the spindle speed using a numerical approach to calculate the average directional cutting force coefficients. The proposed method is capable of predicting the stability lobes accurately for helical milling process where different types of cutting mechanism exist and the axial depth of cut is time varying. It is shown that the numerical predictions agree well with the cutting tests. Finally, the effect of cutting conditions on both the cutting forces and stability limits are thoroughly analyzed.