Measurement and correction of baggy edges on paper … pptx.pdf · Measurement and correction of...

Measurement and correction of baggy edges on paper machinespaper machines

Frédéric Parent & Jean HamelFPInnovations

PaperCon 2011 Page 2454

Outlines

• A few words on baggy edges• Available tools to evaluate baggy edge• Case studies: correction of baggy edges• Conclusions• Conclusions

PaperCon 2011 455

A few words on baggy edges


What is web tension non-uniformity in CD?

Baggy edge= lack of tension= tension drop

l b= longer web= slack edgeEtc.


Issues related to baggy edges

• Print quality problems• MisregistrationMisregistration• Wrinkles/crepe wrinkles• Web breaks• Poor splicing• Poor winding• Web defects such as calender cuts,

crepe wrinkles, etc.


Baggy edge rolls cause web weaving

Lateral oscillations vs CD position0.25

) Baggy edge rolls

0.15

0.2

an p

ositi

on (m

m) Baggy edge rolls

0

0.05

0.1

Stde

v of

med

ia

0A B Y Z


Baggy edge rolls also cause misregistrationRoll median position stability on T12

0.25

0.3

0.35

sitio

n (m

m) Before printing

After printing

0 05

0.1

0.15

0.2

dev

of m

edia

n po

s

0

0.05

X12A202J V06A274C X13A203J Competitor X12A201J X13A195J X13A193J X13A192J

Std

Roll 1 Roll 2 Roll 3 Baggy roll Roll 5 Roll 6 Roll 7 Roll 8

Magenta

Cyan


Baggy edge rolls even cause web breaks!

High tension = Risk of break

2 0

2.5

pli)

Bagginess zone

High tension Risk of break

1.0

1.5

2.0

ensi

on (p

Increasing the average tension

0

0.5

0 5 10 15 20 25 30 35 40 45

CD

Te Increasing the average tension

to reduce the bagginess on press

CD Position (inches)


Origin of bagginess

Force

Longer Spring?L l St t h

Force

= Local Stretch = Bagginess

Bigger or smaller Spring?gg p gNo Bagginess


MD/CD ratio profile

MD/CD ratio

Edge shrinkage effect

F t B k

Edge shrinkage effect

Front Back

Edge rolls usually have more expansion or shrinkage, dge o s usua y a e o e e pa s o o s age,leading to web elongation and bagginess at the edges


Existing tools to evaluate baggy edge


Some mills try to relate baggy edge to roll hardness


Other mills try to relate baggy edge to TSI MD/g

)TSI MD kNm

Mean V.Std Dev.Min

7.5810.1798

7.001 (sho ld be less than 10%)

dex

(kN

m/

8.25

8.50MaxNo Val

7.0017.875

166

(should be less than 10%)

fnes

s In

d

7 50

7.75

8.00

nsile

Stif

f

7.00

7.25

7.50

MD

Te

0 9 19 28 38 47 56 66 756.50

6.75 Edge Edge

CD Position


Existing tools to quantified baggy edge on machine

Beam with air pressure sensors that measure Beam with air pressure sensors that measure air pressure between paper and beam air pressure between paper and beam

Roll with a film force sensors mounted on it Roll with a film force sensors mounted on it in a helical arrangementin a helical arrangementgg

Both pictures have been taken from Metso publications and internet site


Off-line tension beam to quantify baggy edges

• High accuracy (5% error)• Hi h l ti i CD ( 1”)• High resolution in CD (every 1”)• Width 50”


Beam installation on roll tester equipment

Wound out tension

Paper rolls

Wound-out-tension

Lateral

ill ti

CD Tension

oscillations

Measurex

scannerDiameter, roundness scanner,

and length


High resolution measurements in CDTension profiles of paper with baggy streaks - SCA paper

0.4

0.5

n (k

N/m

) cw ccw

0.1

0.2

0.3No

rmal

ized

tens

ion

Tension profiles of dried edges paper - newsprint

00 10 20 30 40 50 60 70 80 90 100 110 120 130

CD position (cm)

p g p p p

0.3

0.4

0.5

sion

(kN/

m)

cw ccw

0.1

0.2

Nor

mal

ized

tens

00 10 20 30 40 50 60 70 80 90 100 110 120 130

CD position (cm)


Roll comparison from different CD positions

Rolls tension profile

0.4

0.5m

)

A B M Y Z

0.2

0.3

Tens

ion

(kN

/m A B M Y Z

0

0.1

0 50 100 150 200

CD position (inches)

CD Position (inches)

Worst Roll for Bagginess


Case studies: correction of baggy edges


Case study #1: Baggy edge (newsprint)

Tension profiles of edge rolls of paper machine0.5

B k dFront edge

0.3

0.4

(kN

/m)

Back edgeFront edge

0.1

0.2

Tens

ion

Tension diff between the 2

sides is 0.3 kN/m

00 10 20 30 40 50 60 70 80 90 100 110 120 130

CD Position (inches) PM front edge PM back edge

Significant baggy edge at the back of the machine


Case study #1: Correcting the drying history

Tension profiles comparison of edge rolls of paper machine0.5

Before correction After correction

0.3

0.4

n (k

N/m

)

Before correction After correction


sides is reduced to 0.1 kN/m

Back edgeFront edge

0.1

0.2

Tens

ion

00 10 20 30 40 50 60 70 80 90 100 110 120 130

CD Position (inches) PM front edge PM back edge

Changing the drying history (press + dryers) allowed to reducethe tension non-uniformity at the back edge


Case study #2: Baggy edge (directory grade)

CD tension profile (STD production)2.5

1.5

2

n ST

(pli)

Front edge roll Back edge roll

0.5

1

Tens

io

00 20 40 60 80 100

CD Position (in)

Significant baggy edge at both edges of the machine


Case study #2: Application of moisture bias

Moisture bias at the edges

0 51

1.52

2.5

as (%

)

Moisture bias(-2% gradual bias

-2-1.5

-1-0.5

00.5

Moi

stur

e bi

a

( gover 50” wide)

-2.50 25 50 75 100 125 150 175 200 225

CD position (inch)

T i fil ith i t bi 2% B k f PM1Tension profile with moisture bias -2% - Back of PM1

2

2.5

3

No bias

With biasTension profile in CD

0.5

1

1.5

Tens

ion

(pli)profile in CD

increases at the edges

0

0 5

0 10 20 30 40 50CD Position (inch) Back PM1 >


Case study #2: Correcting the tension profile with moisture bias

• No biasCD tension profile (STD production)

2

2.5

Front d

Back d- The tension profiles

were not uniform at the edges

0 5

1

1.5

Tens

ion

ST (p

li) edge roll

edge roll

0

0.5

0 20 40 60 80 100

CD Position (in)

• With bias- Tension profiles are

CD tension profile with moisture and caliper bias

2

2.5

li)

Front edge

Back edge- Tension profiles are

improved, especially at the back

0.5

1

1.5

Tens

ion

ST (p

edgeroll

edge roll

00 20 40 60 80 100

CD position (in)

PaperCon 2011 77

Case study #3: Inverse baggy edge (fine paper)

Tension profiles of edge rolls0.5

d

0.3

0.4

kN/m

)


Back edgeFront edge

0.1

0.2

Tens

ion

(k between the 2 sides is 0.2

kN/m

00 10 20 30 40 50 60 70 80 90 100 110 120 130

CD position (inches) PM front edge PM back edge

Inverse baggy edges at each edge of the machineThe customers see baggy edgesggy g


Case study #3: Correcting CD moisture profilesM i t fil t d llMoisture profiles at edges rolls

0.1

0.2

0.3

0.4

vari

atio

n (%

)

-0.3

-0.2

-0.1

0

Moi

stur

e co

nten

t v

Relationship between moisture and CD tension

-0.40 10 20 30 40 50 60 70 80 90 100 110 120 130

CD position (inches)

R2 = 0.7329

0.3

0.4

0.5

kN/m

)Inverse correlation between CD tension and CD moisture profiles(higher moisture = lower tension)

0.1

0.2

Tens

ion

(k

( g )

Correction of CD moisture profiles is underway

0-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3

Moisture variation (%)


What can be achieved

Measurements on any grade of paper Base sheet/coated/laminated Base sheet/coated/laminated

After conversion/print

Different CD positions and sets on paper machinesp p p

Quantification of CD tension profile Quantify how severe is actual bagginess

Comparison with database

Corrections suggested

Analysis and follow-up of machine changes


Conclusions

• A tension beam was developed to quantify CD tension profile of paper web• high accuracy (<5% error)• high accuracy (<5% error)• high resolution (50 units over 127 cm width)

• This new tool was successful in measuring the tensionThis new tool was successful in measuring the tension non-uniformity of different types of paper grades.

• Bagginess and baggy edge can now be quantified at low cost

• Corrections can be made by changing the drying history of the web from the press section to the reelthe web from the press section to the reel.

• The tension beam can be used to monitor the tension profiles corrections and later to ensure the uniformity of the profiles with time.


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