Research On the Load‐Bearing Characteristics of Porous Air Bearings Applied to Ultra‐Precision Spindles

Existing research primarily focuses on small‐to‐medium‐scale porous air bearings, with limited attention given to the large‐scale bearings required for ultra‐precision equipment, such as wafer thinning machines. This study investigates the load‐bearing characteristics of large‐scale porous graphite air bearings used in ultra‐precision spindles. Pressure distribution equations for both the porous material region and the air film region were established by combining gas lubrication theory with Darcy's law under the assumptions of isothermal compressible ideal gas flow. Computational Fluid Dynamics (CFD) was employed to systematically analyze the effects of key parameters—including supply pressure, porous material thickness, average air film thickness, eccentricity, permeability, and rotor speed—on both load‐carrying capacity and air consumption. The results demonstrate that load‐carrying capacity is positively correlated with supply pressure, eccentricity, porous material thickness, average film thickness, and rotor speed, while being negatively correlated with porous material permeability. The bearing air consumption increases with supply pressure, average film thickness, and permeability, but exhibits a non‐linear inverse relationship with the thickness of the porous medium. It remains largely unaffected by eccentricity and rotor speed. This study elucidates the performance evolution of large‐scale porous graphite bearings, providing a theoretical foundation for their optimized design and application in ultra‐precision spindles.