Effect of tool posture on chatter vibration in turn-milling

Turn-milling is a machining method for milling a rotating work material. It has attracted attention as a method for milling difficult-to-cut materials with high efficiency. The milling process enables lower cutting temperature and high chip disposability compared to conventional turning resulting from the interrupted cutting. In addition, turn-milling allows for a larger reduction of workpiece diameter in one tool path due to the higher degree of freedom in the cutting tool posture motion. In order to achieve high-efficiency cutting, it is important to avoid chatter vibration, which has several negative effects, including poor surface quality, machine tool damage, etc. However, few studies have focused on the chatter vibration of turn-milling, and most of those have focused on orthogonal turn-milling. The object of this study is to investigate the effect of tool posture on chatter vibration in 5-axis turn-milling. Instantaneous cutting forces were obtained based on a point cloud simulation model, in which the tool and workpiece are expressed as points, and the chatter stability of turn-milling was predicted by time domain simulation. Cutting experiments were then performed under several conditions with different tool postures, and we confirmed that the predicted chatter stability limits agreed well with the experimental results. In addition, the simulations showed that tool posture has a significant effect on the change in the contact area between the tool and workpiece, which in turn affects the occurrence of chatter vibration.