Technical introduction of high-speed spindle bearings for machine tools (machine tool bearings):
Increasing the speed of the spindle bearings is the key to achieving a high-speed, practical spindle. With the development of high speed, it is efficient for machining machine tools. The rolling element is made of ceramic material, the dmN value is about 20×104, and the numerical control machining center with dmN value of 100×104 under grease lubrication condition is increasing day by day. It has become a development trend, and the oil and oil mist lubrication method will become the future. The development direction of high-speed machine tool spindle bearing lubrication.
1 high-speed spindle bearing development:
Generally, angular contact ball bearings with excellent rigidity and high speed performance are used, in order to meet the high speed requirements of the machine tool spindle. Secondly, cylindrical roller bearings are used.
The dmN value under grease lubrication conditions is 50×104 or less. After the development of oil and gas lubrication, at the same time, gradually develop a compatible lubrication system. From the dmN value of the high-speed performance of the spindle bearing (dm is the diameter of the bearing pitch circle mm × N is the speed r / min. The dmN value has reached 100 × 104 or more. Later, in the bearing, the angle of the rolling element is ceramic Contact ball bearings, after the dmN value of 200 × 104 × 90 years developed spray lubrication, dmN value can reach 300 × 104.
2 high speed spindle bearing technology:
(1) High-speed angular contact ball bearings:
Single row and double row cylindrical roller bearings are inferior to angular contact ball bearings in terms of high speed performance. Angular contact bearings are bearings with contact angles, and tapered roller bearings can be seen. The larger the contact angle, the better the axial stiffness, but since the gyro sliding and the spin sliding between the ball and the raceway are also large, the heat is also increased. In order to improve the speed performance, the method is to reduce the size (or mass) of the ball to change the curvature coefficient of the channel, to reduce the centrifugal force of the ball, reduce the internal load generated during high-speed operation, and increase the number of balls to increase the rigidity.
(2) Ceramic ball angular contact ball bearings:
Hybrid ceramic ball bearings with silicon nitride (Si3N4) ceramics for rolling systems have been introduced, in order to reduce the ball quality and increase the speed. Performance comparison
As a high-speed spindle bearing material, ceramic (Si3N4) has the following advantages: the rolling element generates small centrifugal force and is light in weight when rotating at high speed. Because the density is smaller than the bearing steel. The rotational torque can be reduced, thus reducing the temperature rise and increasing the life. Good thermal conductivity makes it difficult for the rolling elements of ceramic materials to adhere to metals at high speeds. Burns and burns occur when lubrication conditions are good. The thermal expansion is small, and when the rolling elements are in contact with the inner ring, the pre-tightening force is less likely to occur and the clearance is reduced. The deformation of the bearing is small due to high hardness and good rigidity. The rigidity of the spindle is also improved. In summary, therefore, the ceramic material (Si3N4) is used as the rolling element, and the speed can be increased by about 25% and the life of the bearing steel rolling body can be increased by about 3 times.
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