Numerical and experimental analysis of vibration characteristics of spindle system under bearing assembly errors

To research the vibration problem caused by bearing assembly errors in machine tool spindles, a special test rig for rolling bearing misalignment is designed and built. The dynamic model of the spindle-bearing-pedestal system of the test rig is established, and the characterization method for bearing parallel and angular misalignments is given through the Hertz contact theory. The effect rule of the misalignment level on spindle vibration response is studied by simulation and experiment, and the system dynamic model and bearing misalignment model are verified. On this basis, the vibration characteristics of the spindle system under the joint effect of raceway misalignment and waviness are further analyzed. The numerical and experimental results show that when the bearing is in the misalignment state, the excitation of bearing variable compliance increases. The assembly errors of the bearing raceway lead to the deviation of the centroid motion trajectory of the spindle tool end, which seriously affects the machining accuracy of the machine tool. In the case of severe angular misalignment, the system shows chaotic motion, indicating that the instability of the system is enhanced. The impact of angular misalignment on system vibration is greater than parallel misalignment, so bearing ring tilt should be avoided as far as possible in practice. In addition, it is also found that the variation of excitation amplitude of bearing waviness caused by raceway tilt is related to the relationship between the number of waviness and ball number.