Performance of water-lubricated ceramic journal hybrid bearing

Abstract

Strong shear force developed in the lubrication film in the high-speed spindles will resulting high temperature rise and expanding the mandrel, which would arouse safe servicing problem. This study aimed to address the temperature rise issue in spindles through the use of substitutes in the spindle bearing material. To this end, we developed a spindle with a water-lubricated ceramic hydrodynamic and hydrostatic journal bearing. To support the selection of ceramic materials for the water-lubricated journal bearing, we initially performed application-oriented tests; to this end, the water absorption and porosity among alumina, silicon nitride, and silicon carbide were considered. To investigate the performance, and particularly the temperature characteristics of the hybrid bearing, a water-lubricated ceramic hydrodynamic and hydrostatic bearing test rig was designed to include temperature sensors. At the test rig, the radial clearance was measured for solving the temperature distribution of the bearing during the simulation. The experimental results helped verify that the water temperature increased by approximately 0.7°C as the rotation speed increased from 1200 rpm to 5400 rpm without an external radial load. The increase in temperature with and without radial load under a rotation speed of 3600 rpm was compared, and the results revealed a difference of 0.14°C. This indicates that the developed ceramic bearing improves the thermal stability of the spindle which shows its potential for industrial application in machine tools or other high rotation speed machines.