Chatter stability analysis in Micro-milling with aerostatic spindle considering speed effect

The regenerative chatter is one of the fundamental obstacles in high-speed micro-milling process, which causes tool wear and poor surface quality. In order to predict the chatter stability of micro milling with aerostatic spindle more accurately, the effects of rotating speed on the dynamic stiffness and damping coefficients of aerostatic journal bearing are investigated firstly. The frequency response functions (FRFs) of aerostatic spindle under different rotating speeds are calculated considering the speed effect of aerostatic bearing, centrifugal force and gyroscopic moment. A method for calculating the stability lobe diagram (SLD) of micro-milling considering the speed effect is proposed in this paper. The speed-dependent SLD is simulated based on tool tip FRFs under different rotating speeds and is verified by micro-milling of aluminum 7075. In addition, the effects of supply air pressure and air film thickness on the SLD are investigated comprehensively. The results provide guidance to improve the chatter stability and cutting efficiency in micro-milling with aerostatic spindle.