Stiffness, stability, and loss of process damping in high speed machining

As spindles and tool materials have been developed to enable high speed machining operations, success in achieving dramatically higher metal removal rates has been poor, primarily due to the onset of chatter vibrations. The primary reason chatter occurs at high spindle speeds is the loss of the process damping which inhibits regenerative chatter at lower speeds. Essentially, process damping is dependant on the wavelength of the chatter vibration, and this wavelength increases as spindle speed increases. Secondly, there is a reduction in stiffness due to the need to use smaller diameter bearings. All of this points to the need to stiffen spindles as much as possible. Specifically, the stiffness of the tool-spindle connection should be increased. Additionally, even with extremely stiff spindles, there are limitations on MRR and best advantage in high speed machining can only be obtained if cutting operations are performed at optimally stable speeds.