Estimating temperature distribution and heat quantity of spindle shaft for machining centers

The thermal issue of spindles for machining centers is still fundamentally unresolved. Thermal problems due to increased temperature of the spindle shaft lead to thermal displacement of the tool axis and an increase in friction torque, consequently imposing restrictions on spindle speed. To solve this issue, the mainstream method is to predict the temperature rise of the spindle shaft and compensates the thermal displacement that occurs there. However, when developing spindles for machining centers with higher precision and higher speed, it is necessary to take fundamental countermeasures against the temperature rise of the spindle shaft. In order to implement this countermeasure, it is necessary to clarify the phenomenon by measuring how the temperature of the spindle shaft changes due to changes in the spindle speed, and by measuring the temperature of the shaft during high speed rotation. In this paper, it was experimentally confirmed how the shaft temperature changes when a machining center spindle is rotated up to a D(m)n value of 1.53x10(6) mm/min. The results of measuring the spindle shaft temperature revealed that the temperature of the rotor was 2 to 8 K higher than the temperature of the bearing, and there was no positive correlation with the spindle speed. Furthermore, the proposed temperature measurement for the spindle shaft is believed to be applicable to other spindles used in machining tool, serving as an effective method for thermal issue.