The use of rolling bearings on machine tools is mainly used in the following three parts: main shaft, ball screw and general transmission shaft. 1. The rotation accuracy of the spindle system of precision machine tools The bearing accuracy of rolling bearings used on the spindles of precision machine tools should be P5 and above, while for the spindle supports of high-speed and high-precision machine tools such as CNC machine tools and machining centers, ultra-precision bearings of P4 and above should be selected. As the basic accessories of machine tools, the performance of spindle bearings directly affects the speed, rotation accuracy, rigidity, anti-vibration and vibration cutting performance, noise, temperature rise and thermal deformation of machine tools, which in turn affects the precision and surface quality of machined parts. Therefore, high-performance machine tools must be equipped with high-performance bearings. The rotation accuracy of the spindle system refers to the accuracy of the radial runout, cross-section runout and axial runout measured on the reference plane of the front end of the spindle when the machine tool is under no-load manual or motorized low-speed rotation. The accuracy of the spindle system is mainly affected by the following factors: 1) The radial runout of the groove of the bearing ring will correspondingly cause the radial runout of the spindle axis of the spindle system, so that these error parts will be reflected on the machined surface. 2) Inconsistent diameters and shape errors of bearing rolling elements will cause regular errors in the spindle. 3) The side swing of the groove to the end face will cause the axial movement of the main shaft. The axial movement of the main shaft has a particularly significant impact on precision grinding machines, especially bearing grinding machines. If the method of branch groove grinding is used in the process, it will make The scrap rate is greatly increased, and the noise will also be greatly increased. 4) The size and shape error of the bearing installation surface will cause corresponding deformation of the bearing raceway, make the inner and outer rings of the bearing tilt, and make the stiffness of the bearing inconsistent in all directions, thus reducing the rotation accuracy of the spindle system. The end faces of the nuts, spacers, and washers for adjusting the clearance need to be ground, and the perpendicularity to the axis of rotation of the shaft system must correspond to the accuracy of the installed bearings, otherwise the working accuracy of the bearings will be reduced. 2. Lubrication and sealing of precision machine tool spindles We mentioned earlier that lubricant is an important part of the bearing configuration. Different lubrication methods will result in different data on the limit speed of the bearing. The lubricant should be replenished in time according to the design requirements (the grease filling amount of the high-speed precision spindle system is generally 10%~20% of the bearing space), and the reasonable addition of lubricant can reduce the friction and wear of the shaft system and prolong the fatigue life of the bearing. At the same time, it can discharge the frictional heat of the bearing system and play a role in cooling the bearing system; in addition to grease, the lubrication of the bearing system also includes liquid oil lubrication, oil mist lubrication and oil-air lubrication. Oil-air lubrication is used in foreign high-speed spindle systems. Has been widely used, oil-air lubrication is fuel-efficient, pollution-free, and can significantly increase the DN value of the spindle system, and can intelligently control the required amount of lubricant for the shaft system. The design of the main shaft structure, lubrication and sealing must adopt different forms according to different situations. If the seal is worn out, it should be replaced in time. If the contact between the sealing lip and the rotating body exceeds 15m/s, a non-contact sealing structure must be used. Sealing will not only cause friction loss and overheating at the seal contact, but also affect the rotational accuracy of the bearing system. Third, as a precise, efficient and sensitive transmission component, the ball screw should not only use high-precision screw, nut and ball, but also pay attention to the selection of bearings with high axial rigidity, small frictional moment and high running precision. In the past, ball screw supports used bidirectional thrust angular contact ball bearings, tapered roller bearings, combined needle roller and thrust roller bearings, deep groove ball bearings, and thrust ball bearings. At present, single row thrust angular contact ball bearings with a contact angle of 60° are the most widely used for ball screw supports, and the accuracy grade is mainly P4 and above.  

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