Study on Lubrication Method of High Speed Electric Spindle Bearing

The temperature rise of the high-speed rotation electric spindle bearing that can effectively control  is a very important indicator of the electric spindle. The temperature rise of the spindle is closely related to the bearing. The method of reducing the temperature rise of the bearing is: (1) reducing the dynamic friction of the bearing; (2) adjusting and improving the heat dissipation environment of the bearing. There are several methods for lubricating the commonly used electric spindle:

1. Grease lubrication

Generally speaking, the heat output per unit time of bearing increases with the increase of temperature, and the viscosity of lubricating oil decreases accordingly. In order to avoid bearing overheating injury, it is necessary to fully add lubricating oil. But the increase of oil also increases the resistance of stirring, increases the loss of dynamic friction, and thus increases the resistance of motorized spindle. If lubricated with a small amount of grease, not only can not achieve the purpose of low friction, but also can not bring the heat of the bearing. The high-speed rotation of high-speed motorized spindle accelerates the deterioration of grease and reduces the service life of grease.

2. Oil mist lubrication

At present, oil mist Micro-lubrication is mostly used in the lubrication of motorized spindle in high speed grinding of CNC grinding machine. Oil mist lubrication is micro-lubrication, which reduces the friction loss and also reduces the temperature of bearings, and improves the service life of motorized spindle. Another advantage is that there is a certain air pressure inside the bearing seat when the motorized spindle is lubricated by oil mist, which avoids the damage of the motorized spindle caused by abrasive particles entering the motorized spindle housing. However, there are some problems in oil mist lubrication, such as environmental pollution and inaccurate oil control.

3. Oil-air lubrication

Oil-air lubrication has the following characteristics:

(1) It can supply a very small amount of lubricating oil to bearings continuously and steadily.

(2) There is less environmental pollution. The air pollution in the measuring box is about 0.03mg/m after the oil-gas lubricated motorized spindle is put in the propylene box for about 2 hours. Pollution is less than oil mist lubrication because oil-air lubrication has less oil than oil mist lubrication, and lubricant and compressed air flow into bearings in gas-liquid two phases.

(3) It is difficult for dust or moisture and cutting fluid to enter the motorized spindle bearing. Compressed air keeps the positive pressure inside the motorized spindle bearing.