Performance analysis of aerostatic journal micro-bearing and its application to high-speed precision micro-spindles

An aerostatic journal micro-bearing has advantages of simple structure, almost zero friction and increasable load capacity due to aerodynamic pressure effect, which makes it a possible choice for high-speed and precision micro rotatory machines. This study comprehensively investigates the effects of restriction, structure and operation parameters on the performance of an aerostatic journal micro-bearing using numerical models. The numerical models are verified on a prototype aerostatic journal bearing. Considering both the performance requirement and current machining capacity, the restriction parameters of 8-12 mu m in average bearing clearance and 0.08-0.14 mm in orifice diameter are recommended. Another focus of this study is the aerodynamic pressure effect on the performance of micro-bearing, which is thoroughly investigated from the aspects of restriction, structure and operation parameters. The aerodynamic pressure effect is outstanding only at ultra-high speeds and large eccentricities. Two prototypical high-speed precision micro-spindles are developed and their micro-tools with a diameter of 3.175 mm are directly supported by the micro-bearing. The aerodynamic pressure effect resulting from the ultra-high rotational speeds can improve the performance of micro-spindles under loading. However, the low rotational accuracy and balance quality compromise their performance.