Techn Controls Rolling Mill
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Solutions or cold rolling mills Technological controls or cold rolling processes
Rolling o lat metal products is a
complex process where the quality
o the product is infuenced by various
actors like incoming material, mechanical
and electrical equipment, lubrication
material quality and productivity, ABB’s
modular technological control solutions
They are available or all kind o materials
and types o rolling mills:
– Break down mills
material shape and surace, and the homogeneity o stress
distribution. For optimized cost-eiciency and to maximize
material usage, tight tolerances or the thickness are vital, to
enable the strip to be rolled down as closely as possible to the
minimum permissible thickness.
Product quality can only be eectively optimized i the me-
chanical, electrical and instrumentation equipment as well as
the control strategy solution it together.
Comprehensive know-how for cold rolling
ABB has the relevant experience, based on the experience and
knowledge rom more than 800 cold rolling projects, plus the
requisite products and solutions to design this type o equipment
and to put it properly into operation.
– Minimized threading, tail-out and reversing times
– Reduced o gauge length at strip head and tail
Technological controls or cold rolling processes Key components or high-end thickness and latness perormance
Roll gap control
Two bas ic modes, either gap position or total roll orce can
be applied. Selection o mode depends on the type o super-
imposed Automatic Gauge Control (AGC) and the threading
To ensure a constant response time over the whole working
range various process related adaptations and supervisions are
Depending on the sensor concept based on customer needs
dierent thickness control strategies are possible:
– Thickness eedback control
The basic control strategy is thickness eedback (monitor con-
trol) based on the measured thickness deviation at the exit side
o the mill.
The delay t ime, transport o the str ip rom the roll gap to the
thickness gauge, essentially determines the control system’s
dynamic response, particular at low rolling speed. The sot-
ware package provides with a predictive model based option
to improve the dynamic behavior o the thickness eedback
Thickness feed-forward control
With a thickness gauge at the entry side o the roll gap, the
thickness eed-orward control can be applied. It is able to
compensate any thickness deviation caused by changing entry
thickness. A correction value is calculated according to a stored
entry thickness deviation and orwarded to the roll gap control
or interaction when the strip section reaches the roll gap.
Mass flow control
Using the mass fow principle, the outgoing strip thickness at
the instant o rolling can be computed rom the incoming strip
thickness and the in- and out coming strip speeds. By means
o this mass fow control concept, high control accuracy can be
achieved. Thereore it enhances clearly the concepts o thick-
ness eedback and thickness eed orward concerning product
eration and deceleration phases.
Irregularities in roll geometry cause periodic variations in the
roll gap, which can lead to variations in thickness o the rolled
product. The unction compensates or periodic disturbance
rom geometric asymmetries on the backup rolls. An automatic
adaptation to compensate changes during rolling, e.g. due to
thermal eects, wear, loading, etc. is implemented.
Tension feed-forward control
deviations and applies a suitable adjustment to the coiler torque
in order to consider the interactions between roll gap and tension.
1 Speed sensor
2 Thickness gauge
4 ABB strip scanner
5 ABB tension measurement
Speed-tension optimization is used in oil mill applications,
since the strip thickness depends very closely on tension and
rolling speed. In order to achieve maximized material through-
put, the speed o the stand is increased until the strip tension
has reached its control limit or the speed has reached a pre-
selected technological limit value.
AGC for temper mills
Based on the measured elongation and the actual strip dimen-
sions, the elongation control module calculates a correction or
the reerence value o total roll orce and/or tensions.
Coil eccentricity control
oscillations generated by changes in the circularity o the coil.
A major reason or it is the strip head pressed in the slot o the
mandrel. Tension torque corrections are applied at each rota-
tion when the diameter change passes the contact zone o the
strip on the coil.
Adaptive control concepts
The phenomena in the roll gap during rolling process are largely
non-linear and time-variant. In case o system changes or
disturbances ABB uses adaptive controls to modiy the param-
eters accordingly. This adaptation is achieved under considera-
tion o quality and stability criteria or the entire control loop.
Correct strip fatness is essential to ensure an overall product
quality, productivity and successul sub-sequent processing.
Homogeneity o stress distribution and material shape is con-
trolled by ABB’s modular fatness sotware.
The fatness error, given as di erence between the measured
strip fatness and the target curve, can be minimized by modiy-
ing the roll gap with various control unctions, such as roll-
bending and -skewing, shiting o rolls, cooling patterns and
eccentric positioning control or multi-roll stands.
The infuence o each separate type o control action is dened
by evaluated action curves. A least square t o these action
curves to the fatness error results in the most ecient combi-
nation o control actions needed to reduce the fatness devia-
Given the complexity involved in interaction o the nal control
elements and the demanded dynamics, the desired results can
be assured only by automated coordination o all screw-down
reerence values and control commands or strip thickness,
tension and shape.
At any time manual operation such as set-point changes or
selection and de-selection o control loops can be perormed
with bump less transitions.
To ensure highest product quality, ABB is able to simulate the
rolling process based on a non-linear process model. Compari-
son o dierent control strategies based on various sensor and
actuator concepts allows the selection o the best technologi-
cal control solution.
v Velocity dv/dt Acceleration
n Rotation speed FT Strip tension Tq Torque dh Strip thickness deviation
s Roll gap position
En Entry Ex Exit Mdr Mill drive control Coi Coiler control Rol Roll control Dc Tension control Cec Coil eccentricity compensation
Rgc Roll gap control Rbc Roll bending control Rsc Roll shit control Oc Oil lm compensation Ac Automatic fatness control Rec Roll eccentricity control
Thb Thickness eedback control Th Thickness eed-orward control Sp Speed eed-orward control Mc Mass fow control Ten Tension eed-orward control
– Pass scheduling and set-up model
– Threading and unthreading
For more inormation please contact:
ABB Automation GmbH
Industrial Plants – Metals
Kallstadter Straße 1
68309 Mannheim, Germany
Fax: +49 621 381 8055
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