Influence of air cushion throttling structure on support performance of grinding machine based on CFD

As a critical component in the transition of production processes, the support stability of the transport system in the high-end grinding machines significantly impacts the surface quality of the wafer. To guarantee the stability of the transposition system under heavy loads and large floating volumes, an air cushion structure supported by aerostatic pressure with slender holes is proposed. Based on Computational Fluid Dynamics (CFD), the effects of traditional orifices, slender orifices, cylindrical cavity, and square cavity throttling on the air cushion pressure distribution and flow field characteristics were analyzed, determining the superior performance of the slender orifice structure. Furthermore, the influence of structural factors, including throttling hole diameter, number and length-diameter ratio, on air cushion performance and floating displacement is discussed. The findings indicate that, at a film thickness of 34 μm, the slender hole exhibits a bearing capacity 7.28 times higher than that of the small hole, accompanied by a stiffness that is 3.28 times increased. Moreover, for slender holes, a positive correlation is observed between the load capacity and both the diameter and the number of throttling holes, while stiffness is negatively correlated with these parameters. The length-diameter ratio has a negligible influence on both load capacity and stiffness. Building on the above findings, a ceramic-supported air cushion with an orifice diameter of 1 mm was fabricated, and floating displacement measurements were conducted. Under a load of approximately 1000 kg, the air cushion lift exceeded 20 μm, thereby validating its supporting performance. The maximum error compared to the calculated results was less than 5.96 %. The results of the research offer both theoretical underpinning and data evidence for designing air cushions with high bearing capacity and stiffness under conditions of large floating volumes.