Investigations on tool temperature with heat conduction and heat convection in high-speed slot milling of Ti6Al4V

Tool temperature has significant effects on tool wear and tool life in high-speed machining. Salomon hypothesized that increasing cutting speeds would make tool temperature rise to a maximum point and decrease after a certain cutting speed. However, the maximum tool temperature at a certain cutting speed in Salomon’s hypothesis has not been fully validated and widely accepted by academic researchers and industrial engineers. In this paper, a series of experiments for slot milling of Ti6Al4V alloy at different cutting speeds are carried out and tool insert temperatures are measured. The experimental results indicate that the slot milling tool temperature increases first and then decreases as the cutting speed grows. The critical cutting speed is 1500 m/min for slot milling of Ti6Al4V. To analyze the experimental results and find reasons for the decreased milling tool temperature at high cutting speed, we propose a tool temperature prediction model for slot milling insert. The effects of heat convection and heat conduction time on slot milling tool temperature are analyzed. The finite element method is applied to simulate the heat flux and tool-chip contact length under different uncut chip thicknesses. The simulated heat flux is included in the proposed tool temperature prediction model. The variation of tool temperature in the milling process is affected by heat generation, heat conduction time, and convection coefficient. This research demonstrates that the maximum tool temperature at a certain cutting speed in Salomon’s hypothesis can be accepted for interrupted machining processes.