Orifice-restricted hydrostatic thrust bearings are broadly employed in ultra-precision machine tools, aerospace industries, and so forth. The orifice length–diameter ratio (OLDR) is one of the significant geometrical parameters of the orifice-restricted hydrostatic thrust bearing, which directly affects the performance of the bearing. To accurately guide the design of the hydrostatic thrust bearing, the effect of the OLDR on the performance of the hydrostatic thrust bearing needs to be thoroughly and scientifically investigated, especially for ultra-precision machine tools. In this paper, the influences of various OLDRs are comprehensively studied using the computational fluid dynamics (CFD) approach on the pressure pattern, velocity, turbulent intensity, and vortices, as well as the load capacity, stiffness, volume flow rate, and orifice flow resistance of the hydrostatic thrust bearing under identical operating conditions. The obtained results show that there are differences in performance behaviors of the hydrostatic thrust bearing caused by different OLDRs. Some new findings are obtained, particularly in the second-order small vortices which appear in the annular recesses with all OLDRs except that of 2, and the flow resistance does not always increase with increasing OLDRs. Finally, the proposed CFD approach is experimentally validated.

As the applications for freeform optical surfaces continue to grow, the need for high-precision machining methods is becoming more and more of a necessity. Different toolpath strategies for the ultra-high precision turning of freeform surfaces can have a significant impact on the quality of the machined surfaces. This paper presents a novel toolpath planning method for ultra-precision slow tool servo diamond turning based on the curvature of freeform surfaces. The method analyzes the differential geometric properties of freeform surfaces by reconstructing NURBS freeform surfaces. A mathematical model is constructed based on the parameters of different positions of the freeform surface, toolpath parameters, and tool residual height. Appropriate toolpath parameters can be calculated to generate the optical freeform ultra-precision slow tool servo diamond turning toolpath. Compared with the toolpaths generated by the traditional Archimedes spiral method, the ultra-precision slow tool servo diamond turning toolpath planning method proposed in this paper can generate more uniform toolpaths on the freeform surfaces and keep the residual tool height within a small range.

Micro-hole aerostatic bearings have emerged as critical components in ultra-precision machining systems, offering a superior load capacity, stiffness, and stability compared to traditional orifice-based designs. These enhancements are primarily attributed to the high-density configurations of micro-holes and the reduction in hole diameter. However, research on the design and analysis of micro-hole aerostatic bearings for high-rotational-speed applications remains limited. In this study, the finite element method (FEM) was employed to solve the Reynolds equation, thereby conducting a systematic evaluation of the static and high-speed performance characteristics of micro-hole aerostatic thrust bearings. The effects of restrictor types, micro-hole layouts, structural parameters, and centrifugal deformation under high-rotational-speed conditions on bearing performance have been comprehensively examined. The objective of this study is to provide a basis for the design of micro-hole high-speed aerostatic spindles.

The fluid–structure interaction (FSI) effect has a significant impact on the static and dynamic performance of aerostatic spindles, which should be fully considered when developing a new product. To enhance the overall performance of aerostatic spindles, a two-round optimization design method for aerostatic spindles considering the FSI effect is proposed in this article. An aerostatic spindle is optimized to elaborate the design procedure of the proposed method. In the first-round design, the geometrical parameters of the aerostatic bearing were optimized to improve its stiffness. Then, the key structural dimension of the aerostatic spindle is optimized in the second-round design to improve the natural frequency of the spindle. Finally, optimal design parameters are acquired and experimentally verified. This research guides the optimal design of aerostatic spindles considering the FSI effect.

Advancements in manufacturing technology have facilitated the use of micro-orifice restrictors (MORs) in aerostatic bearings. However, the understanding of their effectiveness in journal bearings remains limited. This study utilizes FEM for solving the nonlinear Reynolds equation, incorporating velocity terms, to analyze the characteristics of aerostatic journal bearings (AJBs). The concepts of air impedance and pressure range are introduced and applied to explain the advantages of MORs over traditional orifice restrictors (TORs). Furthermore, the centrifugal deformation of the air film induced by high-speed operations and its consequential impact on bearing performance are methodically examined in detail. Finally, an experimental study is executed to confirm the proposed model and support the pertinent design principles. The experiment indicates that the air film thickness, accounting for centrifugal deformation, aligns more closely with the high-speed operating conditions characteristic of AJBs.

The equilibrium system is essential for the high-precision movement of the ultra-precision vertical axis. However, the complex assembly process makes orifice-throttling frictionless cylinders difficult to manufacture and prone to air hammering. Surface-throttling frictionless pneumatic cylinders effectively avoid these problems. This paper establishes an improved finite element method (FEM) model of a novel surface-throttling frictionless pneumatic cylinder to investigate its static performance. Furthermore, the static equilibrium calculation of the dual-cylinder system is concerned. The radial bearing capacity and support force requirements for the surface-throttling aerostatic bearings are obtained. The outcomes provide theoretical guidance for optimizing cylinder parameters. It ensures that the ultimately optimized cylinder meets the requirements for radial bearing capacity and support force of the ultra-precision vertical axis while minimizing air consumption. Finally, the accuracy of the proposed method is verified through computational fluid dynamics (CFD) calculation and experiments.