Technical Description of Machine Tool High Speed ​​Spindle Bearings (Machine Tool Bearings): Increasing the speed of spindle bearings is the key to achieving a high-speed, practical spindle. With the rapid development of high efficiency for machine tools. Rolling body with ceramic material, dmN value of 20 × 104 or so, under the condition of grease lubrication dmN value of about 100 × 104 CNC machining center is increasing, has become a trend, the use of oil and gas and oil mist lubrication will also become the future Development of High Speed ​​Machine Tool Spindle Bearing Lubrication. 1 high-speed spindle bearing development: Generally use more rigid and high-speed angular contact ball bearings with excellent performance, in order to meet the high-speed requirements of the machine tool spindle. Followed by the use of cylindrical roller bearings. The dmN value under grease lubrication is below 50 × 104. After the development of oil and gas lubrication, at the same time and gradually develop a suitable lubrication system. From the representation of the spindle bearing high speed performance dmN value (dm is the pitch diameter of the bearing mm × N for the speed r / min point of view, the value of dmN has reached more than 100 × 104. Later on the bearing has developed a rolling body of ceramic angle Contact ball bearings, to achieve the dmN value of 200 × 104 × 90 developed jet lubrication, dmN value up to 300 × 104. 2 high-speed spindle bearing technology: (1) high-speed angular contact ball bearings: single row, double row cylindrical roller The sub-bearings are inferior to the angular contact ball bearings in terms of high-speed performance Angular contact bearings are bearings with a contact angle, which can be seen tapered roller bearings. The larger the contact angle the better the axial stiffness, but because the ball and the raceway between Of the gyro sliding and spin sliding is also large, so the heat will increase.In order to improve the speed performance, the method is to reduce the ball size (or mass) to change the curvature coefficient of the channel to reduce the centrifugal force of the ball, reducing high speed operation Resulting in the internal load, while increasing the number of balls to improve rigidity. (2) Ceramic Ball Angular Contact Ball Bearings: The introduction of only rolling system with silicon nitride (Si3N4) ceramic hybrid ceramic ball bearings, in order to reduce the ball The amount to increase the speed of its performance comparison As a high-speed spindle bearing material, ceramic (Si3N4) has the following advantages: high speed rotation of the centrifugal force generated by the rolling small, light weight .Because the density is smaller than the bearing steel .Rotating torque can be reduced, Reduce temperature rise, improve life expectancy. Good thermal conductivity so that ceramic materials, rolling at high speeds difficult to produce adhesion with the metal. Lubrication conditions better resistance to burn, burns. Thermal expansion is small, rolling contact with the inner ring Not easy to occur preload increase lead to reduced clearance Bearings deformation is small, due to high hardness, good rigidity and the rigidity of the spindle has also been improved In summary, the use of ceramic materials (Si3N4) as a rolling body, and Bearing steel rolling body can be increased compared to speed of about 25% 35% life expectancy can be increased about 3 times. (3) The new hybrid angular contact ball bearings: inner ring due to centrifugal force and expansion, high speed rotation contact with the rolling body becomes larger , So that the internal pre-load increases, clearance smaller, increased fever. In response to this problem, recently developed a new inner ring stainless steel hybrid ceramic ball shaft Since the coefficient of linear expansion of stainless steel is 20% smaller than that of bearing steel, it can further control the increase of preload caused by inner ring expansion when the bearing rotates at high speed, and the lubrication condition is abundant, the dmN value can be increased 1.2 times under fixed preload. ) Inner ring is a ceramic hybrid angular contact ball bearings: positioning pre-loaded case, the recent introduction of information. The inner ring also uses ceramic hybrid angular contact ball bearings. Because the inner ring also uses ceramic materials, bearing diameter or The centrifugal expansion of the raceway is small and the increase of the pre-tension is also small. In addition, the rigidity is good, the contact area between the ball and the raceway is small, so the heat generation and expansion are also smaller, and the rotation speed can be higher than that of the ball-only bearing. Is due to high speed rotation of the centrifuge and small expansion, and the metal spindle with the stress if too large may produce damage or even fragmentation. 3 high-speed spindle bearing lubrication: due to the use of simple, economical and widely used, the trend of high-speed spindle bearings for lubrication put forward higher requirements. Conservative grease with a dmN value below 50x104 is widely used due to its ease of use and economy, and requires no special maintenance and no further replenishment, most of which is lifetime lubrication. With the speed increase, dmN value of 100 × 104 or more when using oil and gas mist lubrication, and grease lubrication, the temperature rise is small, can be higher speed rotation, which became the main method of lubrication. The jet lubrication although the dmN value can reach 250 × 104 but requires a lot of lubricating oil, due to the stirring resistance of the power loss, and the need for more complex ancillary equipment, higher interest rates, so generally do not use this lubrication.
