Analysis of axial stiffness characteristics of gas film of porous bidirectional air floating rotary table

As an advanced support structure, hydrostatic air floating rotary table is widely used in high precision machining, measurement and optical system. Its axial stiffness is very important to the stability and accuracy of the system. By combining theoretical modeling, transient simulation and experimental verification, this paper establishes a theoretical analysis model for the upper and lower gas film of the D400 numerical control air-floating rotary table axis, and uses CFD (Computational Fluid Dynamics) dynamic mesh to make the upper and lower gas film reduce the thickness of the gas film at a certain speed. The load curve of the rotary table is fitted according to the load simulation data of the upper and lower gas film, and the stiffness characteristics of the rotary table are obtained. The simulation stiffness analysis of rotary table is verified by design experiment. It is found that the stiffness of upper gas film, lower gas film and rotary table increases first and then decreases, and there is a maximum stiffness. With the increase of gas supply pressure, the load of rotary table increases when it reaches the maximum stiffness. In the experiment, it is also found that the phenomenon of “air floating instability” occurs in the early stage of loading, which should be avoided in high-precision scenarios.