Improvement of the Gas Bearing Stiffness by Higher Supply Pressure (2nd Report)

Abstract

It is required to increase the stiffness of externally pressurized gas bearings. One of the simplest ways to increase the bearing stiffness is to increase the supply pressure. In the first report, authors described the test results of thrust bearings with higher supply pressure. In this report, radial bearings with slot restrictors are tested to examine the possibility and practicality of higher supply pressure. It is proved that the bearing stiffness increases almost linearly with supply pressure as predicted by the theoretical calculation. In case of high stiffness bearings with a small radial clearance, pneumatic hammer instability is not observed and gas flow rate is not a problem so critical. It is confirmed that the increase in supply pressure is the simplest and most practical way to improve the stiffness of externally pressurized gas bearings. A practical high precision spindle head is designed for using high supply pressure. The designed spindle head is expected to have 5 times of stiffness more than present ones of the same class.