Chattering in high pressure roller mills when fed with fine-grained materials

Chattering in high pressure roller mills is caused by the self-exited torsi onal oscillation of the rollers due to irregularities during the intake of feed material into the roller gap. The drive connection between the drive g ear and the driven gear is lost and re-established periodically and the gea rs strike against one another The irregularities begin above a limiting spe ed which depends on the fluidizability of the feed material and decreases w ith increasing fineness of the feed. The chattering frequency lies below th e resonance Frequency of the torsional oscillating system because the perio d is extended by the duration of the phase without drive connection and by the deceleration of the forwards and backwards oscillation due to the remai ning material in the gap. This article shows the measurements of torque, ga l, width grinding force and rotational angle with a high time resolution an d examines the frequency spectra in order to analyze the dynamics of the ch attering.