Abstract: In the process of milling the hardened steel mould of automotive covering parts, the dynamic milling force is larger than others and chattering dither always happens due to its high hardness. Considering the impact of the axial milling force and the centrifugal force which generated by milling spindle system on the interface stiffness of the spindle is in order to bulid accuracy spindle system dynamics model. According to the analysis, the axial milling force has strengthening effect on the interface stiffness of main shaft and the inherent frequency of the main shaft system increases slightly. However, the centrifugal force will soften the interface stiffness. With the increasing spindle speed, the natural frequencies of the system decrease; especially with high speed, the dynamic characteristic of spindle system has a greater deflection. In comparison, softening action of centrifugal force has a more significant influence than the strengthening action of the axial milling force. Therefore, the dynamic characteristics of the main shaft system is still softening during the process of milling than that in static no-load condition. Analysis the impact law of pre-tightening force for interface, cutting tool parameters on spindle system dynamics characteristics to provide the theoretical reference to predict the milling stability for the accurate analysis of the spindle system dynamic characteristic.

Key words: axial milling force, centrifugal force, dynamic characteristic, interface stiffness, spindle system