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 μm 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. •This study establishes the numerical models for the performance calculation of aerostatic journal micro-bearings. Dynamic pressure effect of the bearing is investigated with different rotational speeds and eccentricities. The presented graphs of performance change with restriction, structure and operation parameters provide a comprehensive understanding and design reference for engineers.•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 µm in average bearing clearance and 0.08–0.14 mm in orifice diameter are recommended.•According to the theoretical analysis, a prototype micro-spindle is developed and a micro-bearing with a diameter of 3.175 mm is applied to support the micro-tool. Due to the accommodation of a monolithic flexible coupling, the static load capacity of the micro-tool can be regard as the performance of the micro-bearing. However, the poor machining precision is badly affected its performance. Therefore, another improved prototype mi