High precision electric spindleIt has a wide range of applications, but it also has many problems. Among them, thermal stability is a key issue that needs to be addressed. Why do high-precision electric spindles have thermal stability issues? How to overcome it? Because the electric spindle is made by combining electric spindles, there is no doubt that an additional heat source is added to the structure. Heat dissipation mainly includes losses in the stator winding. The heat generated by the stator winding accounts for more than two-thirds of the total heat of the motor.

The thermal radiation and heat transfer of high-precision electric spindles require reasonable lubrication and cooling of the spindle bearings, otherwise the high-speed operation of the electric spindle cannot be guaranteed. The cooling of the motor is crucial for improving the thermal performance of the electric spindle. A circulating cooling water jacket is designed at the connection between the motor stator and the casing. Water is made of low thermal resistance materials, and the outer ring of the sleeve is equipped with a spiral shaped water tank. When the electric motor is running, circulating cooling water enters the water tank. Strictly controlling the inlet temperature of the cooling water, ensuring a certain pressure and flow rate, can improve the cooling effect. In order to prevent the influence of motor heating on the electric spindle bearings, the electric spindle should use high thermal resistance materials, so that the heat of the motor rotor is mainly transmitted to the transmission shaft through the air gap, and the cooling water maintains the thermal stability balance of the high-precision electric spindle on the transmission shaft.

In order to overcome the disadvantages of the two pre tightening methods mentioned above, a switch type pre tightening method can be adopted in the spindle unit of the ultra high speed machining center for high-precision electric spindles, so that the electric spindle unit can adapt to both low-speed and high load machining, as well as the needs of ultra high speed machining. During low-speed heavy cutting, the bearing operates under a constant directional preload force; During high-speed light cutting, the system can actively switch to constant force pre tightening mode to avoid an increase in pre tightening force and improve the high-speed performance of the bearing.