Introduction

The Fundamentals of Air Bearings
The Challenge of Temperature Fluctuations
Advanced Materials: INVAR
Benefits of INVAR:
- Dimensional Stability: Minimal expansion or contraction with temperature changes, ensuring a consistent air gap and stable bearing performance.
- High Strength and Durability: Maintains structural integrity under varying thermal conditions.
- Thermal Conductivity: Efficient heat dissipation reduces localized thermal stresses.
Experimental Analysis
To evaluate the impact of temperature fluctuations on air bearing performance, a series of tests were conducted using OAV Air Bearings’ OAVTB60i20W temperature-controlled air bearings. These tests measured performance metrics such as load capacity, stiffness, and air gap uniformity under controlled temperature variations.
Key Findings:
- Changes in Diameters: The graphite air bushing’s inside diameter increased by approximately 9.208 microns, while the INVAR shaft’s diameter increased by about 1.8 microns when heated from 25°C to 100°C.
- Clearance: The initial clearance of 18 microns at room temperature increased to approximately 25.408 microns at 100°C.
- Stiffness: The stiffness of the air bearing decreased from 23 N/μm to 17.84 N/μm without air cooling. With effective air cooling, the stiffness decreased to 18.26 N/μm.
Graphs:
1. Changes in Diameters: Graph illustrating the expansion of graphite bushing and INVAR shaft from room temperature to 100°C.
2. Clearance Change: Graph showing the increase in clearance between the graphite bushing and the INVAR shaft with and without air cooling.
3. Stiffness Changes: Graph depicting the stiffness variations of the graphite bushing and INVAR shaft with temperature changes and the effect of air cooling.
Conclusion
Temperature fluctuations pose significant challenges to the performance of air bearings in precision machining. The use of advanced materials like INVAR offers a robust solution by providing exceptional dimensional stability and durability. Experimental results demonstrate that air cooling effectively reduces the thermal expansion of graphite bushings, thereby maintaining tighter tolerances and higher stiffness.
OAV Air Bearings’ high-temperature thrust air bearings exemplify this innovation, designed to operate under extreme environmental conditions without sacrificing precision or quality. As the industry continues to advance, the importance of material selection in designing high-performance air bearings becomes increasingly evident, paving the way for further innovations in precision engineering.
Ayberk Erturk
OAV Air Bearings
Princeton, New Jersey, 08540, USA