| CNC machine tool is the foundation of the high-end equipment manufacturing industry. With the development of science and technology, the machine tool is developing towards to the direction of high speed, high precision. As the core part of the CNC machine, the dynamic performance of the spindle system in the CNC machine has a important influence on the machining accuracy. The bearing, as an important supporting component and with its dynamic precision, directly affects the stability and reliability of the spindle system. In order to improve the machining accuracy of CNC machine tool, it is necessary to analyze the dynamic accuracy of CNC machine tool spindle bearing.In this article, it mainly studies the dynamic precision of angular contact ball bearing. Using the Hertz theory, control theory of rings of rolling bearing, and bearing dynamic analysis method, the movement of the bearing is analyzed. The mechanical model of rolling bearing is established and the relationship between the deformation and load distribution of bearing are studied. The pre-tightening force and the initial contact angle’s influence on the deformation of bearing are studied, and the causes of friction torque are analyzed. The calculation method of friction torque and spin to roll ratio are deduced. The influence of the combined force and rotating speed on the spin to roll ratio, bearing wear and rotation accuracy is investigated.The relationship between the initial contact angle and curvature is gained through analysis. The formula of rolling bearing axial and radial displacement deformation is deduced. With the increase of rotating speed, the radial deformation of bearing increases gradually, the axial deformation is reduced. At the same speed, with the pretightening force becoming large, the radial deformation of bearing is reduced, the axial deformation of bearing becomes larger. When the initial contact angle of rolling bearing is bigger, the radial deformation of bearing is larger, the radial stiffness is smaller, and the axial deformation of Bearing is smaller, the stiffness is bigger. By comparison, the bearing’s spin to roll ratio will increase with the increase of rotating speed. Under the effect of loading, the spin to roll ratio will decrease with the increase of axial force. A large spin to roll ratio will increase the bearing wear and heat, which are disadvantages for bearing accuracy keeping.Hertz elastic contact theory and bearing kinematics theory are applied to calculate the non-linear force caused by rolling bearing. A vibration model of rolling bearing is set up. The vibration characteristic of the bearing is analyzed via the MATLAB programming. The influence of the speed, damping, radial force, rolling element number on the vibration characteristics of bearing system is investigated. The results show that the bearing system response is in periodic and non-periodic form. The increase of the rolling element number and decrease of the radial load can improve the dynamic precision of bearing system. Reasonable design of structure parameters and working parameters can guarantee the stability of the system and improve the dynamic precision of the bearing system. Finally, a CNC machine tool spindle bearing system is experimentally researched. |
