COMPENSATION OF COIL
ECCENTRICITY EFFECTS (CECO)
When metal sheet is wound on to a mandrel the coil is notcompletely round. This eccentricity can be caused by:•• the strip head on the mandrel (belt wrapper)•• the strip coming out from the gripper slot•• reversing mills: After several passes there is a thickness
step from initial thickness at head and tail to the reduced
thickness in the body•• eccentricity of the mandrel itself
This coiler eccentricity causes tension oscillations in thestrip which in turn can lead to thickness errors and surface
defects.
CHALLENGE

Control concept

Since this tension disturbance is repeated with eachrevolution of the winder, its frequency depends on therotational speed of the winder. At high rolling speeds
this periodic tension change is much too fast to becompensated by the closed loop tension controller.
Moreover the behavior of the system to be controlledchanges dramatically with speed, coil diameter, strip
geometry and pass reduction.
OUR SOLUTION
The coil eccentricity compensator CECO is a model
based control which uses the fact that the shape of theeccentricity remains relatively constant during coiling.
It can therefor model the eccentricity over several
revolutions. Using an inverted plant model this eccentricity
is transformed into a compensation torque for the coiler
drive (pre-control).

Structure of the control

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Influence of CECO on strip tension and thickness in a reversing cold mill

PRODUCT FEATURESThe CECO control is designed to adapt to all eccentricities
occurring during winding.

MAIN BENEFITS•• Thanks to the model based approach the CECO is stable
and has a very high compensation rate:•• Better strip quality – stable strip tension leads
to better strip thickness tolerances, betterstrip surface•• For all speeds (up to 22 Hz!)•• Maintenance friendly - using existing sensors
and instrumentation for strip tension andcoiler rotation, no additional sensors or
instrumentation needed•• During acceleration•• For all strip types•• For all coil diameters•• Fast CAPEX- Easy to implement in existingbasic automation environment•• For all pass reductions
The CECO is designed to meet the following restrictions:•• No excitation of the winder shaft resonance frequency•• No risk of exceeding the torque limits•• No tooth-flank rattle to protect the gear box•• Maximum compensation frequency•• Maximum compensation amplitude
SUMMARY
The winder is accelerated by the CECO in such a way thatthe fast diameter changes caused by the coil eccentricity
have no effect on tension and thickness. The model
based approach in combination with the modelling of
the eccentricity over several revolutions enables thecontrol to be stable in all situations and to provide highcompensation rates up to disturbance frequencies of 22Hz.

Primetals Technologies
Austria GmbHA joint venture of Siemens,
Mitsubishi Heavy Industries and Partners
Schuhstr. 60 | 91052 Erlangen | Germany
contact@primetals.com
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Order No. T10-1-N229-L2-P-V2-EN
Printed in Linz | © 02.2018

FIELDS OF APPLICATION•• Unwinder and rewinder of SCM:
Improvement of tension and thickness quality•• Unwinder of batch TCM:
Improvement of tension and thickness quality•• Rewinder of tandem mill or processing lines:
As the coil eccentricity has only a very limited effect onthe thickness the CECO can only improve the tensionquality

The information (including, e.g., figures and numbers) provided in this document contains merely generaldescriptions or characteristics of performance based on estimates and assumptions which have not beenverified. It is no representation, does not constitute and/or evidence a contract or an offer to enter into acontract to any extent and is not binding upon the parties. Any obligation to provide and/or demonstrate
respective characteristics shall only exist if expressly agreed in the terms of the contract. These estimatesand assumptions have to be analyzed on a case-to-case basis and might change as a result of further
product development.
Primetals Technologies excludes any liability whatsoever under or in connection with any provided
information, estimates and assumptions. The provided information, estimates and assumptions shall be
without prejudice to any possible future offer and/or contract. Any use of information provided byPrimetals Technologies to the recipient shall be subject to applicable confidentiality obligations and for theown convenience of and of the sole risk of the recipient.
Primetals Technologies Germany GmbH: Geschäftsführer: Günter Sarcletti, Rolf Riedle, Dr. Martin Fleischer
Firmensitz: Erlangen, Registergericht Fürth, HRB 14815

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Certificate Number:
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