In addition, the high-speed agitation of the motor rotor in the spindle box causes the air inside the cavity to heat up. The heat generated by these heat sources is mainly dissipated through the spindle box and spindle. Therefore, a considerable portion of the heat generated by the motor will be transferred to the bearings through the spindle, thereby affecting the service life of the bearings and causing thermal elongation of the spindle. These frictions will increase with the increase of spindle speed, and the heat generation, temperature rise, and preload of the bearings will also increase, thereby exacerbating the heat generation of the bearings.

In addition, the thermal radiation and conduction of the spindle motor require proper lubrication and cooling of the spindle bearings, otherwise the high-speed operation of the electric spindle cannot be guaranteed. In order to improve the thermal characteristics of the electric spindle, motor cooling is essential. The specific measure is to design a circulating cooling water jacket at the connection between the motor stator and the casing. The water here is made of low thermal resistance materials, and the outer ring of the sleeve is equipped with a spiral water tank. When the motor is working, circulating cooling water is introduced into the water tank. To improve the cooling effect, it is necessary to strictly control the inlet temperature of the cooling water and ensure a certain pressure and flow rate. In order to prevent the motor from overheating and affecting the spindle bearings, the spindle should be made of high thermal resistance materials, so that the heat of the motor rotor is mainly transmitted to the stator through the air gap and absorbed by the cooling water, thereby maintaining the thermal stability balance of the high-speed electric spindle.