Research On Aerostatic Bearing-rotor System Based On High Speed Precision Motorized Spindles

Motorized spindles based on aerostatic bearings have broad application in high precision CNC machine tools because of the advantages such as high speed, high precision and non-pollution. At present, with the speed increases, the speed upgrade of one aerostatic bearing-rotor system is greatly influenced by the dynamic non-linear factors caused by air film, causing the classical theory, which is based on the static linear supporting, not to meet the development requirements of aerostatic bearing-rotor systems.In this paper, the main part of one motorized spindle based on aerostatic bearings, that is the aerostatic bearing-rotor system, is focused on. The flow calculation of aerostatic bearings, the theoretical calculation of the aerostatic bearing-rotor system, the design and establishment of the experiment system, and the experiment validation are carried out by in-depth study. The main research contents include the following aspects:First, for aerostatic bearings, the flow field is calculated with the laminar flow model in the finite volume method based on the N-S equations; the stiffness parameters of the bearings are obtained from the simulation results.Then, according to the non-linear dynamic characteristics of the air film, based on the classical rotor dynamics theory, the finite element calculation scheme of the aerostatic bearing-rotor system's critical speed is proposed. The process of the scheme is to make every parameter of the unsolved frequency equation as close as possible with the corresponding parameter of the frequency equation reflected by the critical speed in actual conditions. After the application of the scheme in one aerostatic bearing-rotor experiment system, the comparison between theoretical and experiment results shows the deviation of first and second critical speed are both less than 10%, which verifies a high accuracy of the scheme.Finally, based on the proposed calculation scheme, an aerostatic bearing-rotor system experiment system is established, in which the aerostatic spherical bearings are applied to the high-speed rotating machinery. From the experiment results, the system is able to go through the second critical speed smoothly but with a bit greater error compared with the designed parameter, which are mainly caused by low machining precision, axial factors and the deviation between the design and actual working conditions, etc.