Development of the spindle shaft for machining center using high thermal conductivity material

Abstract

Due to the high precision and high speed of spindles for machining centers, thermal issues cannot be avoided. The temperature rises of the spindle shaft, which is the rotating component, causes issues such as increased thermal displacement in the tool axis direction and an increase in friction torque, leading to limitations on the spindle speed. Heat removal or heat diffusion methods are effective in reducing the temperature of the spindle shaft. The former method of removing heat from the rotating shaft requires complex peripheral devices for cooling. Here, the latter method of diffusing heat is examined. Specifically, a method for reducing the temperature of the high-temperature part and the temperature difference generated in the shaft will be examined. In order to diffuse the heat of the spindle shaft, it is necessary to increase the thermal conductivity of the shaft. In this study, highly oriented pyrolytic graphite (HOPG), which has recently attracted attention in the semiconductor field, is used for the spindle shaft instead of heat pipes (HP), which are generally used for heat diffusion. The temperatures of the rotor and bearings during rotation of the HOPG spindle shaft and the normal steel spindle shaft were measured. Under the conditions of Dmn value of 1.53×106 mm/min, the hot part of the normal steel spindle shaft is 42°C and the generated temperature difference is 8K. On the other hand, with the HOPG shaft, it was able to reduce to 40°C and the generated temperature difference was reduced to 5K. By using a spindle shaft with high thermal conductivity by HOPG, it was found that the temperature of the high temperature part can be lowered and the temperature difference occurring in the shaft can be reduced.

Keywords

• spindle shaft
• highly oriented pyrolytic graphite (hopg)
• heat pipe (hp)
• thermal conductivity
• heat diffusion
• machining center