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

and control strategies.

For high-end perormance in terms o 

material quality and productivity, ABB’s

modular technological control solutions

are proven and tested in praxis.

 They are available or all kind o materials

and types o rolling mills:

– Break down mills

– Multi-roll mills

– Two-stand mills

– DCR mills

– Tandem mills

– Temper mills

– Foil mills

Significant quality parameters

 The signiicant quality parameters are: material thickness,

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.

Customer Advantages

– Scalable control concept depending on sensor and actuator

concepts

– Tight thickness and latness tolerances over the whole strip

length

– Optimized throughput rates

– In combination with pass scheduling and set-up generation:

– Minimized threading, tail-out and reversing times

– Reduced o gauge length at strip head and tail

 

 Technological controls | ABB

 Technological controls or cold rolling processesKey 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

strategy.

 To ensure a constant response time over the whole working

range various process related adaptations and supervisions are

included.

 AGC for break down mills

Depending on the sensor concept based on customer needs

dierent thickness control strategies are possible:

– Thickness eedback control

– Thickness eed-orward control

– Mass fow control

– Speed eed-orward control

– Roll eccentricity control

– Tension eed-orward control

Thickness feedback 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 

controller signiicantly.

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

quality.

Speed feed-forward control

With the speed eed orward control solution velocity depending

process variations are compensated, in particular in the accel-

eration and deceleration phases.

Roll eccentricity control

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

 The tension eed- orward control responds to entry thickness

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

3 ABB Stressometer or fatness measurement

4 ABB strip scanner

5 ABB tension measurement

1

2

3

4

5

Important sensors in a cold rolling mill

 

 ABB | Technological controls

 AGC for foil mi lls

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

 The coil eccentrici ty compensation minimizes periodic tension

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.

Flatness control

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-

tion.

Coordinated control

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  Velocitydv/dt  Acceleration

 n Rotation speedFT  Strip tensionTq Torquedh Strip thickness deviation

 s Roll gap position

En EntryEx ExitMdr Mill drive controlCoi Coiler controlRol Roll controlDc Tension controlCec Coil eccentricity compensation

Rgc Roll gap controlRbc Roll bending controlRsc Roll shit controlOc Oil lm compensation Ac Automatic fatness controlRec Roll eccentricity control

 Thb Thickness eedback control Th Thickness eed-orward controlSp Speed eed-orward controlMc Mass fow control Ten Tension eed-orward control

Mdr 

Rgc

vr

dhEn

nr

dhEx

RbcRsc

s

Leitwertgeber 

Afc

Tenff 

Coi

RolTq

En

∆TqΕν

F T0

 

Dfc

vEn

dv/dt En

Rol

nEx

Coi

TqEx

Dfc

vEx

dv/dt Ex

F T2

Spff Ofc

Thff 

vEn

vEx

Mfc Thfb

Rec

Cec

nEn

 Thickness control strategy

Speed reference generator

 

Superimposed strategies and solutions are available for:

– Pass scheduling and set-up model

– Threading and unthreading

– Tension, torque and/or roll orce distribution in multi-stand

mills

– Roll gap stabilization to run wedge strip

For more inormation please contact:

 ABB Automation GmbH

Industrial Plants – Metals

Kallstadter Straße 1

68309 Mannheim, Germany

 Teleon: +49 621 381 2596

Fax: +49 621 381 8055

www.abb.com/metals

1 Overview rolling mill

2 Automatic thickness control

3 Flatness control

4 Technological controls by ABB provides the tightest gauge

tolerances

1 2

3 4

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