Development and experimental verification of radial-axial integrated cup-shaped aerostatic bearing for miniature turbine of dental handpiece

Bearings are the key component of the miniature turbine cartridge in dental handpiece and other spindle-turbine systems. The noise, wear and energy loss induced by the friction of conventional ball bearing restrict the performance and reduce the efficiency of the turbine system. As an alternative to conventional ball bearing, the aerostatic type non-contact bearing can greatly improve the turbine cartridge system. In this research, a new radial-axial integrated cup-shaped aerostatic bearing has been developed to minimize the friction and related effects of the turbine cartridge. The new radial-axial bearing is designed and built with composite airway and orifice structures to provide both radial and axial support force on the spindle-turbine. The cup-shaped rotor creates inner and outer radial bearing surface to increase the capacity and stiffness of the bearing. Computer aided design (CAD) and computational fluid dynamic (CFD) software are utilized for evaluating the performance of the developed bearing and the influences of the design parameters. Experiments are conducted for characterizing the operational performance of the newly-developed aerostatic bearing. The improved turbine system with radial-axial aerostatic bearing can reach 76.9krpm of maximum rotational speed, the radial stiffness of 47.3 N/mm, and axial stiffness of 11.63 N/mm.