Material of machine tool spindle bearing

With the continuous increase in the speed requirements of machine tool spindle bearings, on the one hand, improvements are made in the design of the internal structure of the bearings, and on the other hand, new bearing materials have been developed and utilized. At present, hybrid ceramic ball bearings made of silicon nitride ceramics as rolling elements have been widely used in the field of high-speed machine tools. Compared with bearing steel, the density of ceramic material is 40% of steel, and the coefficient of linear expansion is less than 1/4 of steel. Therefore, when the bearing rotates at high speed, for hybrid ceramic ball bearings, the centrifugal force and rotating torque acting on the ball are small, the bearing load caused by the thermal expansion difference between the ball and the ring is relatively relaxed, the bearing friction heat is less, the wear is light, and the high-speed performance is improved. In addition, since the longitudinal elastic modulus of ceramic materials is about 1.5 times that of bearing steel, the rigidity of ceramic ball bearings is greater than that of steel bearings. The limit speed of ceramic ball bearings is 20%～30% higher than steel bearings of the same structure. If the structure of ceramic ball bearings is optimized according to the characteristics of ceramic materials, the limit speed can be higher. This article briefly summarizes the structure type, assembly method, preload, limiting speed, and material selection of the high-speed technology of high-speed machine tool spindle bearings. Due to space limitations, the rigidity and life of the bearing during high-speed rotation cannot be addressed. In fact, the rigidity of the spindle bearings of high-speed machine tools is also an important performance index, but the calculation is very cumbersome, involving many physical quantities, and accurate calculations need to be completed with the help of computers. The life of high-speed machine tool spindle bearings usually refers to the accuracy life, and there is no uniform and recognized method for calculation. Generally, the fatigue life is 30% to 50% as the accuracy life value of the bearing. The demand for high-speed in the machine tool industry is endless. As a way to achieve ultra-high-speed, magnetic bearings have now appeared in the form of spindle support, but from the perspective of operation and cost, the advantages of rolling bearings will continue to be maintained. , And the research and development work to challenge the limit of higher speed still needs to be deepened.