With high-speed machine tool spindle bearing technology introduction - bearing knowledge

With high-speed machine tool spindle bearing technology is introduced, Machine tool bearing) : to improve the speed of the spindle bearing is the key to realize high speed and practical spindle. With the development of high speed, for efficient processing machine tool. Roller adopt ceramic material, dmN value at about 20 x 104, grease lubrication under the condition of dmN value of around 100 x 104 CNC machining center are increasing, has become a development trend of the oil and gas and oil mist lubrication method will become the future development direction of high speed machine tool spindle bearing lubrication. 1 high-speed spindle bearing development: generally use more rigid and good performance of high speed angular contact ball bearing, in order to adapt to the high speed of spindle. The second use cylindrical roller bearing. Under the conditions of grease lubrication dmN value under 50 x 104. To develop oil and gas lubrication, at the same time gradually developed the corresponding lubrication system. From the expression of the main shaft bearing performance of high-speed dmN value ( Dm for bearing pitch diameter mm x N for speed r/min. DmN value has reached more than 100 by 104. Later in the aspect of bearing was developed for the ceramic roller angular contact ball bearings, implements the dmN value is 200 x 104 x 90 s developed after injection lubrication, dmN value can reach 300 by 104. 2 high-speed spindle bearings technology: ( 1) High-speed angular contact ball bearings, single row, double row cylindrical roller bearings are inferior to performance in the high speed angular contact ball bearings. Angular contact bearing is a bearing with contact Angle, it can be seen that tapered roller bearings. Contact Angle, the greater the axial stiffness, the better, but because the gyro sliding between the ball and the raceway and spin slide too big, so the heat will increase. In order to improve the speed performance, the method is to minimize the size of the ball, Or quality) Change the curvature coefficient of the channel, to minimize the ball of the centrifugal force, reduce generated when the high-speed operation of the internal load, at the same time increase the number of the ball in order to improve the rigidity. ( 2) Ceramic ball angular contact ball bearings, launched only rolling system with a silicon nitride ( Si3N4) Hybrid ceramic ball bearing, in order to reduce the quality in order to improve the speed. Its performance is as high speed spindle bearing material, ceramic, Si3N4) Has the following advantages: high speed rotary rolling body produces centrifugal force is small, light weight. Because the density is smaller than bearing steel. Rotary torque can be reduced, thus can reduce the temperature rise, improve the life. Good thermal conductivity of ceramic materials in high speed roller not easy adhesion with metal. Lubrication conditions better resistance to burn, burn. Small thermal expansion, seldom happened when rolling body contact with the inner ring of pre-tightening force increase in clearance. Small deformation of the bearing, due to the high hardness, good rigidity. The spindle rigidity is also improved. To sum up, therefore, the use of ceramic materials ( Si3N4) As a rolling body, compared with the bearing steel roller speed can be increased about 25% 35% life can be improved about 3 times. ( 3) New hybrid angular contact ball bearings, inner ring expansion due to centrifugal force, rotates at a high speed. With roller contact stress, the internal prestressing load increase and decrease of clearance, fever. Aiming at this problem, recently developed for stainless steel inner ring of new hybrid ceramic ball bearing. Due to the linear expansion coefficient of stainless steel is 20% less than bearing steel and thus to further control the bearing rotates at high speed due to inner ring expansion of pre-load increasing. Values of dmN under lubrication condition, fixed pre-load 1 can be improved. 2 times. ( 4) Inner ring to the mixture of ceramic angular contact ball bearing: positioning preloading tight situation, recent data is introduced. Inner ring also use ceramic material of hybrid angular contact ball bearings. Because the inner ring also use ceramic material, bearing inside diameter or raceway small centrifugal expansion, the increase of preloaded also smaller, coupled with good rigidity, ball and raceway contact area is small, so the fever and inflation also small, can only for ceramic ball bearing to a higher speed than. But when it is due to the high speed rotating centrifugal and expansion is small, and the cooperation between metal spindle stress too much could damage or even fracture. 3 high speed spindle bearing lubrication: due to the use of simple, economical and widely used, the high speed spindle bearing development trend puts forward higher requirements on lubrication. Conservative dmN value under 50 x 104 grease lubrication, due to the use of simple, economical and widely used, and no need special maintenance, no subsequent complement, most of them are permanently lubricated. Along with the speed increase, dmN value more than 100 x 104 with oil and gas and oil mist lubrication, when compared with grease lubrication, temperature rise is small, can rotate at higher speed, thus become the main method of lubrication. And although injection lubrication dmN value can reach 250 by 104 but need a lot of lubricating oil, stirring resistance makes the power loss is bigger, and requires more complex accessory equipment, high interest, so you don't normally use the lubrication method.