Relationship between dynamic characteristics of air film of aerostatic spindle and mid-frequency of surface topography

The dynamic characteristics of the gas film of an aerostatic spindle primary affect workpiece waviness in ultra-precision machining. To improve the machining accuracy of the machine tool and provide a firm theoretical basis for the design of an aerostatic spindle, a simulation model combining transient computational fluid dynamics (CFD) analysis and transient dynamic analysis is established in this study to investigate the dynamic characteristics of the spindle under unstable operating conditions. Based on a large eddy simulation, a three-dimensional flow model of an air film in an aerostatic spindle is established. The simulation results show that the gas flow in the throttle chamber is turbulent, and that complex vortices are formed. Using dynamic grid modeling technology, a CFD numerical model for the unsteady calculation of the spindle is established, and the dynamic characteristics of the gas film are obtained. A transient dynamic simulation model of an aerostatic spindle is established, and the effect of the nonlinear dynamic characteristics of the gas film on the spindle displacement response is investigated. Subsequently, a surface morphology prediction model is established. Results show that film fluctuation significantly affects the dynamic characteristics of the spindle and subsequently affects the generation of surface ripples on the workpiece.