Effect of balls' quantities, preload and raceway diameters on rotation accuracy and vibration of rigid rotor-bearing system based on nonlinear dynamic model

The rotation accuracy and vibration of the bearing-rotor system are important evaluation indicators for the working accuracy of machine tools. In this work, an innovative nonlinear dynamic model of the ball bearingrotor system is first developed by considering the slip, spin and gyroscopic effects of ball and the whirl motion of cage. Secondly, this developed model is validated through experimental methods. On this basis, the coordination of balls' quantities and preload is studied to obtain the desired rotation accuracy and vibration of rotor. The effect of raceway diameters on the rotation accuracy and vibration of rotor is investigated. The influence mechanism of the odd and even number of balls in the left and right bearings on the rotation accuracy and vibration is revealed. The analyzed results illustrate that the reasonable contact load of the ball by adjusting the preload of the bearing-rotor system or the balls' quantity can prompt good rotation accuracy and low vibration of rotor, here, the maximum contact loads of 65 N should be adopted in the left and right bearings to select the preload. Additionally, odd or even balls assembled in the left and right bearings synchronously are conducive to obtaining a favorable trajectory and rotating accuracy of rotor.