EFFECT OF ACTIVE AERODYNAMIC BEARING ON PERFORMANCE OF HIGH-SPEED PRECISION AIR-BEARING SPINDLE

A novel hybrid high-speed air-bearing spindle is proposed for improving the performance of small-diameter cutting and grinding tools. In addition to an ordinary aerostatic thrust/radial bearing, proposed air-bearing spindle employs an active aerodynamic bearing for suppressing the spindle vibration at high rotational speed. Based on an analysis using a prototype air-bearing spindle, this active high-speed air-bearing spindle has following improvements: (1) decrease the spindle weight by using new-ceramic sialon, (2) replace the conventional induction built-in motor by a synchronous built-in motor, and (3) insert a band-pass filter in the control system for adjusting the time-delay of active controlling. It is shown in the analysis for the spindle performance that the vibration of the spindle can be suppressed to be less than 0.05 mu m up to the rotational speed of 500Hz (30,000min(-1)) by the active control of the wedge angle on the aerodynamic bearing surface. Final goal of the study for improving the performance of this active high-speed precision air-bearing tool spindle is to suppress the amplitude of the spindle vibration to be less than 0.1 mu m at the maximum rotational speed of 2kHz (120,000min(-1)). Tactics for attaining this goal is discussed.