Abstract: Aimed at the characteristics of variable cutting depth and thickness due to complex motion in orthogonal turn-milling, the 3D chatter theoretical model is proposed by using mathematic method based on orthogonal turn-milling principle. The chatter stability lobes of the orthogonal and eccentric turn-milling are predicted in the frequency domain using the proposed analytical solution, which the chatter condition in orthogonal turn-milling is closed relative to both cutter speed and depth of cut, besides cutter geometry, engagement conditions, frequency response function, material property of workpiece and so on. The results of spectrum analysis of cutting force in the experiment of orthogonal turn-milling chatter stability process show that the process is chatter free and stable when the spectrum is dominated by the tooth passing frequency. Chatter is occurred when the spectrum is dominated by the modal frequencies of system structure, and cutting force and surface roughness are higher in chatter conditions than in chatter free conditions. Therefore, the chatter stability of orthogonal turn-milling can be predicted by using the theoretical model and simulation results,and a theoretical guidance is provided for machined surface quality and machining efficiency.

Key words: Chatter stability, Eccentric machining, Modeling, Orthogonal turn-milling