Motor Spindle Modeling and Experimental Characterization

Efficiency of milling operations is often limited by cutting process dynamic instability, that restrains the achievable Material Removal Rate. In order to forecast machining performance it is necessary to consider all key elements that mostly influence instability, due to regenerative chatter: for high speed machining the spindle probably the most significant of them. This work describes a sequence of experimental tests and numerical models conceived to build and update a reliable dynamic model of a motorized spindle bearing assembly. Different setups have been analyzed by experimental modal analysis in order to characterize how the motor rotor, the tool clamping system, the bearings preload piston influence the spindle dynamic behavior. The goal is to define a set of modeling guidelines, to be used while designing future generations of spindles. Experimental results are used to update a beam finite element model of the spindle. Bearing preload, cutting forces and tool clamping force effects on modal parameters have been also studied.