Measurement and correction of baggy edges on
paper machines
Frédéric Parent & Jean Hamel
FPInnovations
PaperCon 2011 Page 2454
Outlines
•
•
•
•
A few words on baggy edges
Available tools to evaluate baggy edge
Case studies: correction of baggy edges
Conclusions
PaperCon 2011 Page 2455
A few words on baggy edges
PaperCon 2011 Page 2456
What is web tension non-uniformity in CD?
Baggy edge
= lack of tension
= tension drop
= longer
l
web
b
= slack edge
Etc.
PaperCon 2011 Page 2457
Issues related to baggy edges
•
•
•
•
•
•
•
Print quality problems
Misregistration
Wrinkles/crepe wrinkles
Web breaks
Poor splicing
Poor winding
Web defects such as calender cuts,
crepe wrinkles, etc.
PaperCon 2011 Page 2458
Baggy edge rolls cause web weaving
Lateral oscillations vs CD position
Stdev of media
an position (mm))
0.25
Baggy edge rolls
0.2
0.15
0.1
0.05
0
A
B
PaperCon 2011 Page 2459
Y
Z
Baggy edge rolls also cause misregistration
Roll median position stability on T12
Std
dev of median pos
sition (mm)
0.35
Before printing
0.3
After printing
0.25
0.2
0.15
0.1
0 05
0.05
0
X12A202J
V06A274C
X13A203J
Competitor
X13A195J
X13A193J
X13A192J
Roll 1
Roll 2
Roll 3
Baggy roll X12A201J
Roll 5
Roll 6
Roll 7
Roll 8
Magenta
Cyan
PaperCon 2011 Page 2460
Baggy edge rolls even cause web breaks!
High tension = Risk of break
CD Te
ension (p
pli)
Bagginess zone
2.5
20
2.0
1.5
1.0
Increasing the average tension
to reduce the bagginess on press
0.5
0
0
5
10
15
20
25
CD Position (inches)
PaperCon 2011 Page 2461
30
35
40
45
Origin of bagginess
Force
Longer Spring?
= Local
L
l Stretch
St t h
= Bagginess
Force
Bigger
gg or smaller Spring?
p g
No Bagginess
PaperCon 2011 Page 2462
MD/CD ratio profile
MD/CD ratio
Edge shrinkage effect
F t
Front
B k
Back
Edge
dge rolls
o s usua
usually
y have
a e more
oee
expansion
pa s o o
or sshrinkage,
age,
leading to web elongation and bagginess at the edges
PaperCon 2011 Page 2463
Existing tools to evaluate baggy edge
PaperCon 2011 Page 2464
Some mills try to relate baggy edge to roll hardness
PaperCon 2011 Page 2465
Other mills try to relate baggy edge to TSI MD
MD Tensile Stifffness Ind
dex (kNm//g)
TSI MD
kNm
Mean V.
7.581
Std Dev. 0.1798
Min
7.001
Max
7.875
No Val
166
8.50
(sho ld be less than 10%)
(should
8.25
8.00
7.75
7 50
7.50
7.25
7.00
6.75
6.50
Edge
0
9
Edge
19
28
38
CD Position
PaperCon 2011 Page 2466
47
56
66
75
Existing tools to quantified baggy edge on machine
Beam with air pressure sensors that measure
air pressure between paper and beam
Roll with a film force sensors mounted on it
in a helical arrangement
g
Both pictures have
been taken from
Metso publications
and internet site
PaperCon 2011 Page 2467
Off-line tension beam to quantify baggy edges
•
•
•
High accuracy (5% error)
Hi h resolution
High
l ti in
i CD (every
(
1”)
Width 50”
PaperCon 2011 Page 2468
Beam installation on roll tester equipment
Wound out tension
Wound-out-tension
Paper rolls
Lateral
oscillations
ill ti
CD Tension
Measurex
Diameter,, roundness
scanner
and length
PaperCon 2011 Page 2469
High resolution measurements in CD
Tension profiles of paper with baggy streaks - SCA paper
Normalized tension
n (kN/m)
0.5
cw
ccw
0.4
0.3
0.2
0.1
0
0
10
20
30
40
50
60
70
80
90
100
110
120
130
CD position (cm)
Tension p
profiles of dried edges
g paper
p p - newsprint
p
0.5
Normalized tens
sion (kN/m)
cw
ccw
0.4
0.3
0.2
0.1
0
0
10
20
30
40
50
60
70
CD position (cm)
PaperCon 2011 Page 2470
80
90
100
110
120
130
Roll comparison from different CD positions
Rolls tension profile
Tension (kN/m
m)
0.5
0.4
A
B
M
Y
Z
150
200
0.3
0.2
0.1
0
0
50
100
CD Position (inches)
CD position (inches)
Worst Roll for Bagginess
PaperCon 2011 Page 2471
Case studies: correction of baggy edges
PaperCon 2011 Page 2472
Case study #1: Baggy edge (newsprint)
Tension profiles of edge rolls of paper machine
0.5
Front edge
B k edge
Back
d
Tension (kN/m )
0.4
0.3
Tension diff
between the 2
sides is 0.3 kN/m
0.2
0.1
0
0
10
20
 PM front edge
30
40
50
60
70
80
CD Position (inches)
90
100
110
120
PM back edge 
Significant baggy edge at the back of the machine
PaperCon 2011 Page 2473
130
Case study #1: Correcting the drying history
Tension profiles comparison of edge rolls of paper machine
0.5
 Before correction
Tension
n (kN/m)
0.4
 After correction
Tension diff
between the 2
sides is reduced to
0.1 kN/m
Front edge
0.3
Back edge
0.2
0.1
0
0
10
20
 PM front edge
30
40
50
60
70
80
CD Position (inches)
90
100
110
120
130
PM back edge 
Changing the drying history (press + dryers) allowed to reduce
the tension non-uniformity at the back edge
PaperCon 2011 Page 2474
Case study #2: Baggy edge (directory grade)
CD tension profile (STD production)
2.5
Tensio n ST (pli)
2
Back edge roll
Front edge roll
1.5
1
0.5
0
0
20
40
60
80
100
CD Position (in)
Significant baggy edge at both edges of the machine
PaperCon 2011 Page 2475
Case study #2: Application of moisture bias
Moisture bias
((-2% g
gradual bias
over 50” wide)
0
25
50
75
100
125
150
175
200
225
CD position (inch)
T
Tension
i profile
fil with
ith moisture
i t
bias
bi -2%
2% - Back
B k off PM1
3
Tension
profile in CD
increases at
the edges
No bias
2.5
With bias
2
Tension (pli)
Moisture bia
as (%)
Moisture bias at the edges
2.5
2
1.5
1
05
0.5
0
-0.5
-1
-1.5
-2
-2.5
1.5
1
0.5
0
5
0
0
10
PaperCon 2011 Page 2476
20
CD Position (inch)
30
40
50
Back PM1 >
Case study #2: Correcting the tension profile
with moisture bias
CD tension profile (STD production)
No bias
-
The tension profiles
were not uniform at
the edges
Front
edge
d
roll
2
Tension ST (pli)
•
2.5
1.5
Back
edge
d
roll
1
05
0.5
0
0
20
40
60
80
100
CD Position (in)
CD tension profile with moisture and caliper bias
With bias
-
Tension profiles are
improved, especially
at the back
Front
edge
roll
2
Tension ST (pli)
•
2.5
1.5
Back
edge
roll
1
0.5
0
0
20
PaperCon 2011 Page 2477
40
60
CD position (in)
80
100
Case study #3: Inverse baggy edge (fine paper)
Tension profiles of edge rolls
0.5
Front edge
d
Back edge
T ensio n (kkN/m )
0.4
0.3
Tension diff
between the 2
sides is 0.2
kN/m
0.2
0.1
0
0
10
20
 PM front edge
30
40
50
60
70
80
CD position (inches)
90
100
110
120
PM back edge 
Inverse baggy edges at each edge of the machine
The customers see baggy
ggy edges
g
PaperCon 2011 Page 2478
130
Case study #3: Correcting CD moisture profiles
M i t
Moisture
profiles
fil att edges
d
rolls
ll
Moisture content v
variation (%)
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
0
10
20
30
40
50
60
70
80
90
100
110
120
130
CD position (inches)
Relationship between moisture and CD tension
0.5
Correction of CD moisture profiles
is underway
0.4
Tension (k
kN/m)
Inverse correlation between CD
tension and CD moisture profiles
((higher
g
moisture = lower tension))
R2 = 0.7329
0.3
0.2
0.1
0
-0.4
-0.3
-0.2
-0.1
0
Moisture variation (%)
PaperCon 2011 Page 2479
0.1
0.2
0.3
What can be achieved
 Measurements on any grade of paper
 Base sheet/coated/laminated
 After conversion/print
positions and sets on p
paper
p machines
Different CD p
 Quantification
of CD tension profile
 Quantify how severe is actual bagginess
 Comparison with database
 Corrections suggested
 Analysis and follow-up of machine changes
PaperCon 2011 Page 2480
Conclusions
• A tension beam was developed to quantify CD tension
profile of paper web
• high accuracy (<5% error)
• high resolution (50 units over 127 cm width)
• This 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 reel
reel.
• The tension beam can be used to monitor the tension
profiles corrections and later to ensure the uniformity of the
profiles with time.
PaperCon 2011 Page 2481