Rotor Cooling – Cooling of motor spindle shafts

Electrical losses of the motor, friction losses of the bearings and also heat from the machining process itself lead to thermal loads on motor spindles. The cooling of spindles is usually done by liquids flowing through the spindle housing. This cooling concept effectively reduces the housing temperature but has no significant effect on the temperature of the spindle shaft. However, heating of the shaft is critical as it is disproportionately high compared to the housing. This results in an increase of the temperature difference between the inner and outer bearing rings. Depending on the applied bearing arrangement, this in turn leads to undesired variation of the bearing preload during the machining process. One possible consequence is surface defects on the workpiece. The IFW is developing a novel cooling concept based on convective heat transfer between rotating and static lamellar heat exchangers. The heat is transferred from the rotating system (shaft) to the static system through small air gaps. The heat is finally dissipated using the existing cooling channels within the spindle housing.