Chip formation and its effects on cutting force, tool temperature, tool stress, and cutting edge wear in high- and ultra-high-speed milling

In the present study, experimental tests and finite element simulation were conducted in order to investigate chip formation and its effects on cutting force, tool temperature, tool stress, and cutting edge wear in high- and ultra-high-speed (v = 200-2000 m/min) milling. It was found that the serration of chip became more and more obvious as the cutting speed increased. Most of the saw-tooth chip was separated at the cutting speed of 2000 m/min. During the formation process of the separated saw-tooth, the high temperature in the shear band had substantial effect on the initiation of the crack in the chip. When the cutting speed increased, the formation frequency of the saw-tooth increased with decreasing growth rate and the tool-chip contact length exhibited a decreasing trend. At each cutting speed used in the present work, the fluctuation frequency of cutting force, tool temperature, and tool stress was consistent with that of the saw-tooth formation. The saw-tooth formation which led to periodically changing cutting thickness had great effects on the cyclical fluctuations of the cutting force, tool temperature, and tool stress. When the cutting speed increased from 650 to 2000 m/min, the amplitude of the cutting force and tool temperature grew 116 and 93 %, respectively. The higher degree of chip serration at higher cutting speed resulted in the substantial change of the cutting thickness, leading to greater mechanical and thermal impact. The tool temperature had greater effect on the tool stress than the cutting force did when the cutting speed was relatively high. Due to the small tool-chip contact length at cutting speeds of 1550 and 2000 m/min, no obvious wear appeared on the tool rake face. Because of the higher average value and the higher amplitude of tool stress at the cutting speed of 2000 m/min, chipping emerged on the tool cutting edge. This phenomenon was not found on the cutting edge when the cutting speed was 1550 m/min.