Hydrostatic thrust bearings are the core part of the hydrostatic spindle, which is widely used in high precision grinding machines. In this paper, the viscosity-temperature (v-t) characteristics of hydrostatic oil are systematically investigated, which is essential for improving the performance of the hydrostatic thrust bearing and the spindle working at high pressure and high rotational speed. Based on the computational fluid dynamics (CFD) simulation developed, the performance variation rules of thrust bearing surface are established while changing the oil supply pressure. It is found that the bearing capacity and temperature are obviously affected by varying viscosity-temperature characteristics, which have significant fluctuation phenomenon at the orifice. Furthermore, the turbulence intensity of the taper hole is found the least factor by analyzing four kinds of commonly used orifice type configurations. Finally, comparing the simulation and experimental results, the v-t model developed is proofed well matching with the experiment. The model can provide a basis for accurate design and analysis of hydrostatic thrust bearings and consequently the effective design and analysis of the hydrostatic spindle for high precision grinding machine.

https://www.mdpi.com/2075-1702/10/2/127/pdf?version=1644577116

Design of a Hydrostatic Spindle and Its Simulation Analysis with the Application to a High Precision Internal Grinding Machine

Effects of oil recess structural parameters on comprehensive tribological properties in multi-pad hydrostatic thrust bearing for CNC vertical processing equipment based on low power consumption

Slide stability is key to the aerostatic guide in ultra-precise machines; thus, it has garnered plenty of attention. Macro-scale studies are commonplace, but micro- and nano-vibration issues require more attention. Microscope vibration is mainly caused by tiny changes in the fluid parameters of lubricating gas film, which is complex and has no verdict. In this case, slide-gas interaction should be considered. In this study, the widely used orifice-type restrictor was investigated for its nano-vibration performance. A Comsol finite-element-method fluid–structure interaction model was used to simulate and analyze an orifice-type restrictor, and orifice-restrictor vibration characteristics at the nanometer scale were inspected using a high-performance laser vibrometer. The results demonstrate that see-saw mode vibrations occur in the restrictors, growing stronger with increased air-supply pressure. The see-saw vibration’s axis is speculatively determined based on orifice and restrictor structures, and the vibration type is related to the number of orifices. The results also show that the vibration is random with natural frequencies at the kilohertz level. The newly provided research results are beneficial for better understanding the nano-vibrations of orifice-type restrictors.

Experimental Study of See-Saw Mode Nano-Vibration on Orifice-Type Restrictors

Abstract The design of a hydrostatic bearing pad is limited to simple geometry using analytical equations or one-parameter optimization based on experimental data. This study proposes and investigates a new two-parameter method for estimating optimal hydrostatic bearing pad proportions—recess area and position, using Computational Fluid Dynamics (CFD). In this study, 3D static CFD quarter model of a multi-recess hydrostatic bearing pad assuming laminar flow is used. The CFD model was calibrated based on experimentally obtained results and the literature. The recess pressure and resulting load are evaluated for a variety of recess positions and areas. Performance factors are calculated and interpolated in the MATLAB environment. Using the proposed novel two-parameter optimization, the energetic loss was reduced by 20% compared to the classical one-parameter approach. This methodology allows versatile and effective design of optimal hydrostatic bearings operating in low-speed conditions to achieve minimum energetic loss. 

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A Novel Geometry Optimization Approach for Multi-Recess Hydrostatic Bearing Pad Operating in Static and low-Speed Conditions Using CFD Simulation

Abstract This study investigates a new two-parameter method for estimating optimal hydrostatic bearing pad proportions. The design of a hydrostatic bearing pad is limited to simple geometry using analytical equations or one-parameter optimization based on experimental data. In this study, 3D static CFD model results were verified using analytical results and experimental data on a hydrostatic bearing testing device. The obtained CFD results for load and pressure show a deviation within 5.2% compared to the experimentally obtained results and the literature. Using the proposed novel two-parameter optimisation, the energetic loss was reduced by 30% compared to the classical one-parameter approach. This methodology allows versatile and effective design of optimal hydrostatic bearings operating in low-speed conditions to achieve minimum energetic loss. 

/pdf/a-novel-geometry-optimization-approach-for-multi-recess-1vojtl3k.pdf

A novel geometry optimization approach for multi-recess hydrostatic bearing pad operating in static and low-speed conditions using CFD simulation

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.

https://www.mdpi.com/2076-3417/11/3/959/pdf

CFD-Based Investigation on Effects of Orifice Length–Diameter Ratio for the Design of Hydrostatic Thrust Bearings

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

Qiang Gao

Papers

CFD-Based Investigation on Effects of Orifice Length–Diameter Ratio for the Design of Hydrostatic Thrust Bearings

A Two-Round Optimization Design Method for Aerostatic Spindles Considering the Fluid–Structure Interaction Effect