Frequency modulation of high-speed mill chatter

Mill chatter is a notorious condition in the high-speed strip rolling process, having a behavior that is complex and changeful. During fieldwork to measure the vibration in high-speed rolling mills, a frequency modulation phenomenon was identified, which had not been reported in the strip rolling community. This article makes a theoretical investigation of the newly encountered phenomenon in the strip rolling process. According to an analysis of the mill roller bearings, the periodic change of stiffness of the bearings at the fixed load orientation, together with the periodic change of the effective errors of the bearings, may cause amplitude and frequency modulation, based on the theories of Fourier series and Bessel functions. The comparison between test results and theoretical analysis implies that the frequency modulation is caused by the effective errors of the mill roller bearings, that have 12 ripples on the internal ring.