# Research Developments of Aerostatic Thrust Bearings: A Review
## 5 The Applications of ATBs  
### High Precision Applications  
High-precision applications using ATBs mainly include precision machine tools and precision flotation equipment. A large number of mature products have been developed and produced. Moore and Precitch in the United States, Fanuc in Japan, the Loxham Precision Company, Cranfield University in the United Kingdom, the Harbin Institute of Technology in China, and other institutions have developed a variety of high-precision machine tools and mature commercial products. The Nanotech 250 UPL and Nanotech 450 UPL ultra-precision machine tools were developed by the Moore company, adopting impact-resistant air bearing spindles, as shown in Figure 15 [99,100]. The motion accuracy of machine tools is no more than 12.5 nm at 10 krpm. Precitch's Nanoform X small-frame diamond lathe adopts HS150 and HS75 spindles [101], as shown in Figure 15. The surface roughness of the workpiece is less than 1 nm. The axial stiffness of the HS75 spindle is 105 N/\(\upmu\)m. The maximum speed of this working spindle is 18 krpm. Axial/radial motion accuracy is less than 20 nm. The axial stiffness of the HS150 spindle is 230 N/\(\upmu\)m. The maximum working speed is 10 krpm. Axial/radial motion accuracy is less than 15 nm. Fanuc has successfully developed a ROBONANO \(\upalpha\)-0 iB five-axis ultra-precision nanomachine [102]. This machine tool is supported by the aerostatic bearing, and the rotation accuracy can reach 0.05 \(\upmu\)m. Both the B-axis and C-axis can achieve 360-degree continuous rotation. [PERSON] [103] has developed an Ultra precision six-axis ultra-precision machine, named \(\upmu\)6. The guideway system is supported by ATBs. The surface roughness is less than 5 nm during turning cutting and less than 10 nm during micro washing. In addition, study on precision machine tools has been carried out by many research institutions. A three-axis ultra-precision machine tool has been successfully developed by the Tokyo Institute of Technology [104,105], named ANGEL. A new air bearing platform  
Figure 15: High precision machine tools. (**a**) Nanotech 450 UPL. (**b**) Nanoform X [100,101]. is applied in this machine, and the Z axis is supported by the ATB. The max machined workpiece size is 230 mm \(\times\) 230 mm \(\times\) 70 mm. Groove machining with a precision of 20 nm can be realized. National Cheng-Kung university [5] has developed a pneumatic servo table. The sliding guideway is supported by the ATB. The positioning accuracy of the platform can reach 0.04 \(\upmu\)m. A small ultra-precision milling machine for micro parts has been developed by Brunel University of the UK [106; 107], named Ultramil. Both the spindle and the linear guideway are supported by aerostatic bearings. The motion accuracy of the linear axis of the machine tool is less than 1 \(\upmu\)m. The rotation accuracy of the turntable is less than 1\({}^{\prime\prime}\) (1/3600 degree), and the motion accuracy of the other rotation axis is less than 10\({}^{\prime\prime}\). For microgroove machining based on the diamond tool, surface roughness can reach 10 nm and straightness error can reach 0.28 \(\upmu\)m/40 mm. The Beijing Institute of Aeronautical Precision Machinery [108] has successfully developed an ultra-precision lathe, named Nanosys-300. The aspheric machining accuracy is between 0.3 and 0.5 \(\upmu\)m, and surface roughness is less than 0.01 \(\upmu\)m. The Institute of Mechanical Manufacturing Technology, Chinese Academy of Sciences [108] has developed an aerostatic lathe spindle. Two aerostatic journal bearings and a thrust bearing are integrated to support the spindle. The roundness of the cutting brass (H62) parts is less than 0.1 \(\upmu\)m, and the surface roughness can reach 0.03 \(\upmu\)m. Cranfield University [109] has developed a six-axis ultra-precision machine tool, named Integ-\(\upmu\)4. A self-developed porous ATB is adopted in this machine. It has a linear motion resolution of 1 nm and a rotational motion resolution of less than 1 \(\times\) 10\({}^{-8}\) rad.