Effectively controlling the temperature rise of the high-speed rotating electric spindle bearing is a very important indicator of the electric spindle, and the temperature rise of the spindle is closely related to the bearing. The method to reduce the temperature rise of the bearing is: (1) reduce the dynamic friction of the bearing; (2) adjust and improve the heat dissipation environment of the bearing. Commonly used electric spindle lubrication has the following methods:
1. Grease lubrication
Under normal circumstances, the calorific value per unit time of the bearing increases as the temperature rises, and the viscosity of the lubricating oil will decrease accordingly. In order to avoid bearing overheating and injury, it is necessary to fully add lubricating oil. However, the increase in oil volume also increases the resistance of stirring and increases the dynamic friction loss, thereby increasing the resistance of the electric spindle. If a small amount of grease is used for lubrication, not only will it not achieve the purpose of low friction, it will also not bring out the heat of the bearing. The high-speed rotation of the high-speed electric spindle accelerates the deterioration of the grease and reduces the service life of the grease.
2. Oil mist lubrication
At present, the lubrication of the electric spindle in the high-speed grinding of the CNC grinder mostly adopts oil mist micro-lubrication. Oil mist lubrication is the micro-lubrication, which reduces the friction loss and also reduces the temperature of the bearing and increases the service life of the electric spindle. Another advantage is that due to the oil mist lubrication of the electric spindle, the inside of the bearing seat has a certain air pressure, which avoids the damage of the electric spindle caused by the abrasive particles entering the shaft shell of the electric spindle. However, oil mist lubrication has problems of environmental pollution and inaccurate oil control.
3. Oil-air lubrication
Oil-air lubrication has the following characteristics:
(1) A very small amount of lubricating oil can be continuously and stably supplied to the bearing;
(2) Less environmental pollution. After placing the oil-air-lubricated electric spindle in a propylene box for about 2 hours, the air pollution level in the measuring box is about 0.03 mg/m. Pollution is less than that of oil mist lubrication. The reason is that oil-air lubrication has less oil than oil mist lubrication, and the lubricating oil and compressed air flow into the bearing in two phases.
(3) It is difficult for dust or moisture and cutting fluid to enter the bearing of the electric spindle. The compressed air keeps the positive pressure inside the bearing of the electric spindle.
Link to this article：Explore bearing lubrication methods for high-speed electric spindles
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