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5th-octave mode chatter problems, by contrast,
can usually be traced to a specific exciter such
as a gear mesh or chock bearing vibration, so
the first part of our investigation is focused on
tracing these exciters. Premature marking of the
back-up rolls is often a symptom of 5th-octave
mode chatter when the speed ranges of the mill are such that the vibration from the exciters is magnified by resonances of the work rolls. In this case, UNIVIB is able to prepare a stability chart from measured responses on the mill. This can be used by the operators to select the most stable speeds of operation.

Investigations have been carried out on more than 25 rolling mills in all corners of the world. Go to our Downloads page where you can obtain our reference list. We also offer a range of monitoring systems that can be used to manage mill chatter problems - visit our AVAS for rolling mills page
Our investigations have covered both 3rd and 5th octave mode chatter problems. The former involves the sudden excitation of a resonant mode of the entire roll stack and our investigations will generally include a modal analysis, the results of which are extremely useful in identifying how the mill is vibrating - as can be seen from the mode shape reproduced on the left.
UNIVIB engineers have nearly 20 years experience in the troubleshooting of all types of strip chatter and mill vibration problem. We specialise in the "hands-on" (or should that be "hands-dirty") measurement and analysis of the way a mill actually behaves under normal operating conditions, rather than trying to predict its characteristics from mathematical models. All of our investigations are carried on on-site, using portable instrumentation. Most of our investigations have naturally been carried out on cold rolling mills, where surface quality is of prime importance. However, a number of investigations have also been carried out on hot rolling mill finishing stands and associated equipment.