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12-1-2000
An Investigation into the effect of plate hardness,
and surface speed differential on flexographic gear
marking
Wisit Wirojrungson
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Recommended Citation
Wirojrungson, Wisit, "An Investigation into the effect of plate hardness, and surface speed differential on flexographic gear marking"
(2000). Thesis. Rochester Institute of Technology. Accessed from
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An Investigation into the Effect
of
Plate Hardness,
Flexographic Gear
and
Surface Speed Differential
Marking
by
Wisit Wirojrungson
fulfillment of the
of Science in the
School of Printing Management and Sciences in the College
of
Imaging Arts and Sciences of the
Rochester Institute of Technology
A thesis
submitted
requirements
in
partial
for the degree
of
Master
December 2000
Thesis Advisor: Professor
Barry Lee
on
School of Printing Management and Sciences
Rochester Institute of Technology
Rochester, New York
Certificate of Approval
Master's Thesis
This is to certify that the Master's Thesis of
Wisit Wirojrungson
With a major in Printing Technology
has been approved by the Thesis Committee as satisfactory
for the thesis requirement for the Master of Science degree
at the convocation of
b-eC:en1ber
ld.)
date
Thesis Committee:
Barry Lee
Thesis Advisor
Leonard W. Lager
Graduate Program Coordinator
Frank Romano
Director or Designate
~OOO
Permission to Reproduced
An Investigation into the Effect of Plate Hardness and Surface Speed Differential on
Flexographic Gear Marking
I, Wisit Wirojrungson, hereby grant permission to the Wallace Memorial Library of the
Rochester Institute of Technology to reproduce my thesis in whole or in part. Any
reproduction will not be for commercial use or profit.
Date:
\'2./11 hOOD
Signature of Author
Acknowledgements
This thesis
would not
individuals
following
have been
possible without
whose contribution was
the
the
great assistance of
invaluable for the
completion of
this thesis.
Professor
Barry Lee,
Printing Management
devoting
writing
and
the thesis
Sciences
invaluable time for
guidance and
assistance
and
in using
at
Imaging
at
of
of
and
of
Technology, for
for providing the
the Technical
and
Education Center
of
of
Technology, for
the
the
Verity IA software for gear mark quantitative evaluation,
a staff at
the Rochester Institute
the School
this thesis
the Rochester Institute
of
Mr. Voraphot Vacheravothan,
of
the Rochester Institute
critical review of
a scientist at
Mr. David Dembroski,
Sciences
at
the School
suggestions,
Mr. Daniel Clark,
Graphic Art
advisor and a professor at
Printing
the School
of
Technology, for
and
Management
Ms. Ornsiri
and
Printing
and
the assistance in pressruns,
Thonggoom,
Sciences
Management
at
graduate students
the Rochester Institute
of
Technology and my best friends, for their encouragement along the way,
Siam
Pulp Public Company Limited for financial support on my education at
the Rochester Institute
All of the
of
Technology,
observers who participated
in
press sheet visual
My father and my mother who always stand by me.
iii
evaluation,
and
Table
List
of
Tables
List
of
Figures
of
Contents
vi
vii
Abstract
viii
Chapter 1 Introduction
1-5
Purpose
and
Rationale for
1
Study
Surface Speed
2
Durometer
3
Endnotes for Chapter One
5
Chapter 2 Theoretical Basis
Flexographic
6-23
6
Printing
Flexographic Gears
Gears
13
Gear Materials
17
Types
Gear
8
of
17
Marking
Endnotes for Chapter Two
22
24-31
Chapter 3 Literature Review
Endnotes for Chapter Three
31
IV
Chapter 4 Hypotheses
32-33
Chapter 5
34-40
Methodology
Chapter 6 Results
and
Analyses
41-45
Chapter 7 Conclusions
46-48
Bibliography
49-50
Appendices
51-59
Appendix A
Platemaking Standards
52
Appendix B Visual Analysis Test Form
54
Appendix C Data
56
and
Statistics
List
Table 6.1 Surface Speed
(Average)
Table 6.2 Two-Factor ANOVA
of
Tables
Measured
with
the Tachometer
43
Summary Table
Table 6.3 Gaussian Abscissae, Interval
Scale,
and
42
Standard Errors
44
Table A
Platemaking Standards
44
Table B
Horizontal Bar Defect Indices
57
Table C ANOVA for Horizontal Bar Defect Indices
57
Table D Visual Evaluation by A
58
Group of Observers
VI
List
of
Figures
Figure 2.1 Flexographic Unit
Figure 2.2 Gear
on
7
Plate Cylinder
10
Figure 2.3 Flexographic Unit
12
Figure 2.4 Spur Gears
13
Figure 2.5 Bevel Gears
13
Figure 2.6 Worm Gears
14
Figure 2.7 Helical Gear
15
Figure 2.8 Anti-Backlash Spur Gears
16
Figure 5.1 Test Target
35
vn
Abstract
Gear marking is
pattern
a print
defect in flexography. It
lateral alternating dark
of
and
corresponding to the distance between
characterizes gear
debris,
or other
marking
mechanical system of
the
different factors.
most
press.
gear
web
spaced
length
teeth. A comprehensive definition
Gear marking
to
metal
burrs,
movement somewhere
unsmooth
cases, gear
uniformly
light bands along the
as a regular pattern attributable
flaws that lead to
In
appears as a
can
be
caused
results
marking
by
from
nicks,
in the
a multitude of
more
than
one
phenomenon.
The
objective of
contribute
factors
speed
mark
this study
to both the
studied
was
causes and
was
The test target
the
plate
the dependent
were
narrow-web press.
severity
designed
image
variable of
To study the
effect of surface speed
0.020 inch,
of
were used
to
the
flexographic
and
Vlll
in
were expected
gear marking.
hardness,
the
to
The
and surface
substrate when gear
study.
hardness,
of
Andy 4120
three
60 Shore A,
two types
create variations
plate
the RIT's Mark
effect of plate
differential,
factors that
area and
and printed on
different hardness, 40 Shore A, 50 Shore A,
the
some
(independent variables) included
differential between the
severity
to investigate
plate
System
types
were used.
with
To study
stickybacks, 0.015 inch
surface speed
differentials.
and
Six
pressruns were
mounted on
mounted on
A group
of
0.015-inch
0.020-inch
thirty
to participate in
in terms
plate
hardness
stickybacks and the others were of three plate
hardness
performed; the first three
pressruns were of
three
stickybacks.
observers at
the Rochester Institute
press sheet visual evaluation
of gear mark severity.
horizontal bar defect indices
The
Verity IA
on
sample
Technology were
asked
by ranking six sample press
sheets
of
software was used
sheets
of
six
to
measure
the
for the
pressruns
quantitative analysis of gear mark severity.
The
results
affected
hardness
the
indicated that
gear mark
a
hardness
severity in
and
flexography
will produce more noticeable
higher differential in
than
plate
in
gear
differential in
surface
significantly.
A lower
marking than
surface speed will produce more noticeable
lower differential.
IX
a
higher
in
gear
speed
plate
one.
A
marking
Chapter 1
Introduction
Purpose
and
Rationale for
Flexographic printing
or
in
It
current
day
usage.
has developed into
growth rate of
growing
print
packaging
6-7%
a
Study
flexography
started as a
a year
1
and enjoys
subject of
appears as a
light bands along the
teeth. The
45%.
problem
is clearly
definition
an estimated
considered
is especially
the fastest
popular
market opportunities
and
method and
in the
because
higher quality
of
its
prints
this research, is
a print
spaced pattern of
defect in flexographic
lateral alternating dark
length corresponding to the distance between
"Gear marking is to
comprehensive
With
processes
process.
uniformly
web
printing
printing
process.
quality improvements. Higher
from this dynamic printing
It
process
expanding
result
of
A., flexography is
This printing
efficiencies and
printing.
rubber-stamp type
in the U. S.
many
Gear Marking, the
the important
one of
sophisticated, high quality
technology.
industry
is
observed
in
flexography
characterizes
screens of
as
the
marking
gear
mid-tone range of 30-
ghosting is to
gear
and
as
a
letterpress."2
A
regular pattern
to
attributable
metal
burrs,
movement somewhere
follows
that
pattern of
no
debris,
nicks,
in the
mechanical system of
discernible pattern,
alternating dark
flaws that lead to
or other
and
the
marking is the
gear
light bands along the
press.
unsmooth
Unlike
banding
occurrence of a regular
web
length that follows the
gear pitch.
Gear marking
gear
marking
be
can
results
caused
from
not produce gear marks
in
one station
in
either.
the
and
web
The
not
the
cylinders so
low
more
all
a multitude of
than one
cases,
in another;
Generally,
impression
high
but
in
by
problem
far
phenomenon.
and one
another
is
off pitch
type
type
of
of
ink
associated
One
ink may
and
most
cases,
print station
may
produce gear marks
will not produce gear marks
with
running the
line that the impression
the alternating dark
and creates
different factors. In
light bands
plate
and
pressure alternates
on
the
prints
along
length.
objective of
contribute
this study
to both the
factors that
plate
a solution could
image
be
to investigate some factors that
causes and
were studied
between the
was
the
included
area and
severity
plate
the
of
flexographic
hardness
substrate.
were expected
gear marking.
and surface speed
Ultimately, it
to
The
differential
was expected
that
provided.
Surface Speed
In the printing process,
station
registering
each color station needs
with one another.
"To
prevent
to
print
cleanly,
with each
smearing, the surface speed
of
the plate cylinder,
Therefore,
If any
these three rollers
them is
one of
severe
printing
the
Matching
through the
use of a gear power
however,
new
order
slurring,
has
to
halos,
been
not yet
for
be
a
the
wiping
will result.
accomplished
technology using
speed
largely successful.
not run at
as well as
wear,
smearing,
are also used
than the anilox roller to create
squeeze off excess
and
plate
Servo-drive
transmission.
identical."3
be
create equal surface speeds.
rollers with the web can
the way, is the only one that does
at a slower speed
in
together to
the cylinders
technology
cylinder must
slightly different rate,
these three
motors on all
by
at a
problems such as
independent
roller,
are geared
turning
speed of
this
impression
anilox roller and
matching;
The fountain
but turns
press speed
action against
the latter
inks.
Durometer
Durometer is the
curing.
measurement of rubber
Photopolymers,
Shore durometer is the
"It
measures
load."4
spring
durometers
industry
The
are
for
most common
most
of a
widely
the instruments
determining
and
durometer is
used
for harder
frustum
used
most
used
hundred. For
zero
plate
durometer in the 45-55 Shore A
one
a
cone
into the
generally
for
general
used
plates after
of
hardness.
plate
hardness.
variety
rubber surface under
Shore durometer is the
"A"
type.
soft-rubber
range.
of
hardness.
testing; the Shore
The durometer hardness
printing
"D"
scale runs
paper, plastic, printers
Rough
Shore
in the flexographic
printing
rubber roll and rubber plate
products."5
from
to
flexographic
instrument for measuring
specifying
"The Shore A durometer is
of
materials, are available in
or plate
the indentation
hardness
select
and uneven substrates such
as corrugated
Shore A
board, however,
range.
hardness
Today,
available
Published
from
materials
nonexistent.
It is
there
related
expected
process.
are a
lower durometer hardness in the 20-40
variety
of materials with
different durometer
photopolymer manufacturers.
to
gear
that this
industry's awareness, and,
flexographic
require
at
the
marking
study
least,
will
will
are
still
difficult to find
or
heighten the flexographic printing
increase the understanding
of
the
Endnotes for Chapter One
1.
Training Needs Survey for the Flexographic Printing Industry:
Expectations (CPCC 572
Piedmont
2.
Michael
3.
(4th
4/98) [Brochure], (n.d.). Charlotte,
Growth
NC: Central
Community College.
Utschig, S. (1991). Gear Marking. A technical paper by courtesy
Wiest, FTA/FFTA.
p.
1.
Siconofli, F. N. (Ed), (1997).
Flexography: Principles
Ed.). Ronkonkoma, NY: Foundation
Association,
p.
28.
4.
Ibid.
p.
118.
5.
Ibid.
p.
118.
of
of
and
Flexographic Technical
Practices.
Chapter 2
Theoretical Basis
Flexographic
Printing
Flexographic printing
flexible
relief
mountable
to
ink metering
fast
image
or
flexography is
a
direct rotary printing
plates of rubber or photopolymer material.
plate cylinders of various repeat
roll or anilox
drying fluid
nonabsorbent.
method
ink to
roller,
For every
with or without a
that
plates
lengths,
print on a
revolution of
the
inked
doctor
variety
printing
of
The
plates are
by a cell-structured
blade,
and
substrates,
plate
that uses
carrying
a
absorbent or
cylinder,
an
image is
produced.
A typical flexographic printing
2.1):
in
(A)
Ink fountain
most two-roll
plate cylinder
(F)
pan
inking
(B)
station consists of
Ink fountain
system)
Substrate
(G)
(D)
roller
following elements
(C)
Doctor blade (not included
Ink metering
Impression
(Figure
the
cylinder.
or anilox roller
(E) Printing
Figure 2.1 Flexographic Unit
Flexographic printing
and
results
the
from the interaction
printing
plate
supplies
ink to the ink fountain
roller.
The
This is
accomplished
the
the excess ink
higher
with a
with a
a
the land
area of
of
the
cell on
the
the
lower
cell count.
areas of
the
light impression
two-roll
Once the
against
ink is
squeezed off
speed
than the
fountain roller,
by
means of
anilox roller
by
plate.
The
to
cell count per
the
impression
amount of
with
roller
turning
create a
the
one
that
plate.
or
laser
scrapes off
anilox
linear inch
ink. A
and
roller with
than one
the substrate,
pressing it
to transfer ink.
rubber
wiping
pan
ink to the printing plate,
the doctor blade is not
the way, is the only
mechanically
the
anilox
ink to the printing
which are smaller and shallower
the impression
inking system where
of
anilox roller applies
plate make an
ink,
Ink remaining in the
anilox roller.
cells,
roller, the
The doctor blade
anilox roller.
anilox roller affects
cell count contains more
the inked
In
on
the flow
uniform cell structured
the
entire surface of
anilox
The ink is then transferred to the
roller.
through the
the
printing, the ink-fountain
perform
is then transferred to the printing
dimension
a
To
anilox roller meters and controls
engraved on
cells
substrate.
of
usually used, the
fountain
roller at a slower
action against
does
excess
not run at
the latter.
the
The
press speed.
The
anilox roller and
same
surface speed.
cylinder's, the
smearing
of
Yet,
the impression
anilox roller's and
the
to travel
geared together
cylinder's must match
Otherwise,
substrate's.
the
slurring,
at
the
plate
halos,
and plate wear will result.
Flexography
variety
have to be
the plate cylinder
is
a versatile
substrates, from
Flexographic inks
water-based
printing
corrugated
inks
solvent-based
spot color and process color
jobs
can
board to
types
compatible with all
inks,
The
process.
process can print on a wide
plastic
film,
or even
of substrates are
toilet
available,
and ultraviolet-light-sensitive
be
paper.
including
inks. Both
flexographically.
printed
Flexographic Gears
A
is
gear
from
the
a
toothed wheel, usually
one part of a machine
turning
gears of
to
different diameters,
On flexographic presses, the
and gears
the
another.
of one shaft will cause
transmit the
the
to the
the
on or
gear
very
teeth.
near
The
the
pitch
pitch circle
printing
is exactly
The
meshed,
meshing two
obtained."1
Gears
rollers.
the length
surface of
to the
By
torque is
imaginary circle
equal
gears are
to the impression
inking
length,
two
rotate.
power
and
cylinder.
circle, the
to
of
speed and
delivers
print repeat
by exactly one revolution of the plate
located
other shaft
in both
main motor
determine the
plate cylinders
"When the teeth
a variation
power
that transmits motion
mounted on a shaft
rollers
used on
of print created
the
plates must
around
gears print
the
be
center of
length.
Gear
is the distance between
pitch
diameter, from the
gear's pitch
Diametrical
teeth
adjacent
on a
as measured
gear,
The
same point on each tooth.
pitch
Number
=
of
printing
of
diameter is the diameter
pitch
the
equal
inking
and
gear
that propels
to the diameter
cylinder while
diameter
of
quality
is
rotate
The
the
the
of
pitch
top
the
the
printing
will create a speed
"If
that roller to rotate at a
before the
faster than
that
shafts.
gear
driving
Flexographic
gear
the
the
the
pitch
diameter
plate cylinder gear
is
to the
plate
is identical to the
outer
plate mounted
their
gears always operate on
mismatch, which causes print
one gear
slower speed
diameter position, the
the
is
set past
the
than desired.
roller
pitch
If
that it turns
one
will
or worn
they
be
when
mounted
permanently
the flexographic
will affect
press operators mount
it
anilox roller are mounted on
driving the anilox roller is mounted permanently while the
gears are precise parts of
and remove
the
plate cylinder and
plate cylinder can
become damaged
flexography
"All impression,
desired."3
propel
The
their
pitch
of
match
anilox roller gear
It is important that
they
otherwise,
of
of
diameter
pitch
(inch)
gears operate.
have their diameters
The
diameter
anilox roller.
will cause
meshed
gears
shaft,
them."2
the
problems and excessive plate wear.
diameter it
gear
the
diameter;
pitch
rollers must
at which
follows.
teeth
Pitch diameter
The
equation
along the
the
the
gear
the job is finished
print
printing
quality
temporarily
so
that
or
temporarily.
system.
and register.
on
the
If
they
Most
plate cylinder
they can purchase
one set of
gears
for
the
all
possibility
of
of
print a
job to
a gear
for
reduce
the
that
gear
only
recommended
mounted."5
to the
the
that
print
the
Another
quality
gear
gear set on
the
plate
of
its
is
color
A
gear
permanently
plate cylinder
gear.
to
Although using
long
Therefore, "it is
cylinder
the
the
needed
money in the
register.
plate
is
on
be permanently
plate cylinder
delivers
anilox roller.
shows a gear mounted on
mounted on
shaft.
that
opposite side of
Figure 2.2 Gear
Figure 2.2
the
money, it may save
the
increases the
frequently."4
damage to the
and
driving
wear and
"temporary
are used
they
when
wear and potential
each plate cylinder costs more
by improving
power
faster tooth
press operators mount
and use
shaft,
it. However,
matches
the gears, because
damaging
flexography
plate cylinder
run
that
of plate cylinder gears creates
mounting
minority
sets of plate cylinders
The
the bare
cylinder
cylinder's
on
the
Plate Cylinder
shaft of a plate cylinder.
that is driven
printing diameter
diameter. The printing diameter is the diameter
twice the thickness
of
the
mounted plates.
10
The
The printing
by a gear attached
must match
of
the bare
at
the
end
the gear's pitch
plate cylinder plus
combination of
the bare cylinder
diameter
the
gear
plus stickyback and
driving
from any
being
the cylinder.
turned
offset
by
this
the
following
If the
the
of
,
,
.
thickness
diameter
pitch
is the formula
for any
stickyback
Plate
diameter
The bare
diameter
rubber plate
difference between the
_,,
pitch
pitch
diameter
of
measuring its
by
the bare
gear and
diameter
of
be determined
of a gear can
cylinder
be determined
gear can
pitch
builds up to the
plates
the
cylinder
The
surface.
cylinder
diameter
by the combined thickness of the printing plates and mounting material.
Therefore,
The
The
standard gear publication.
difference between the
is
printing
,
,
,
.
plates
the
and
would
could not obtain good
increase the printing
be
roller.
impression
gear off
either
the
to determine the ideal thickness for
plate and
plate
its
plate
zero
to turn
printing
pressure
This
impression
increasing
diameter.
gear and
the bare
of gear
-
Bare
plate cylinder
diameter
=
plate cylinder's gear was set
by
be half the
cylinder
the
of
Pitch diameter
,
thickness
measurements, there
squeeze,
material will
mounting
plate cylinder.
plus stickyback
mounted
used
and
would
pitch
printing
on
its
across
by
however,
cylinder,
pitch
and
diameter. If the
around
plate
cylinder
plate cylinder's gear
to
the diameter
mounting height.
of
Usually,
11
closer
would
to the
mesh with
allow
for
corrugated
industry
the
plate
their plate cylinders or
the
the
press operator
the cylinder, he
diameter. Therefore, flexographers
increasing
exactly these
pressure or plate squeeze when
moving the
force the
were
by
adds
0.005 inch to the
narrow-web
plate
printing
thickness to
is
the
at
turning
web speed
at a
slightly different rate, there
only be
squeeze
the
and
plate cylinder and the anilox roller all must rotate
in the flexographic
printing
well as excessive plate wear.
web can
for impression
0.002 inch.
adds
"The impression cylinder, the
exactly
allow
Matching
will
the
be
process.
severe
If any
printing
these three
speed of
one of
them
problems as
the
rollers with
accomplished through the use of a gear power transmission
system."6
Impression*"
"oiler
\f^
/
...
Plate
Z^^rountiin
Cyl./^tf ^
R0ner
Anilox to]
Figure 2.3 Gear Train
Figure 2.3
shows
independent
have
an
motor
flexographic
rollers,
gear
motors on all
infinite
drives
the
repeat
train
the plate
capability;
on plate cylinders
presses
main
flexographic
but,
has
not
been
a gear
motor
press.
that
to date the
incremental
drive
Flexographic Press
cylinders so
have been using
and still possess an
transmitted from the
on a
on a
a
flexographic
use of
largely
train to
power
the
repeat capability.
electric
Therefore,
all
plate and anilox
Power is
rollers.
use
press could
independent
successful.
to the impression
12
The ideal is to
always
The impression
roller's
rotary
power
is then transmitted to the
plate cylinders and anilox rollers
through gears.
The
gear system
system
all
that turns the
three
Types
The
that turns the impression
rotating
of
parts
"A
spur gear
gears are used
has
straight
to the face
to transmit
to transmit
power
teeth,
of
power
from the
gears
the
pitch of
the
include spur, bevel
which are machined
gear."7
between
the
gears on
plate cylinder
a condition where
worm and
along the
helical
axis of
the
It is depicted in Figure 2.4. Spur
parallel shafts.
to the
They
are
generally
anilox roller.
Figure 2.5 Bevel Gears
Figure 2.4 Spur Gears
Backlash,
However,
gear
same.
flexographic
gear or at right angles
used
is the
is different from the
Gears
most common
types.
plate and anilox rollers.
rollers
there are too large spaces between successive gear
teeth, is detrimental to high quality printing
13
and can occur on all
types
of gears.
It
allows
the
position of
drive cylinders,
the driven
cylinder
which creates misregister.
to
It
change
also
in
reference
increases the
to the
plate
other
bounce
problem.
"Bevel
angles
gears are used
(90
degrees),
to
to transmit
other."8
each
to
gears are almost never used
shafts of
these
gears are used
device; they
are
has
in
an
a
The helical
limited
a
differential
relation
to the
important
and
which are at right
bevel
plate or anilox rollers,
to the impression
incorporated into
direct drive flexographic process,
has
the
shows a set of
roller
in the indirect impression drum drive
register correction system
presses
between two shafts,
Figure 2.5
power
rollers are parallel
register of one plate cylinder
360 degree.
power
gear
(drum)
box
which can change
advantage over
this is its ability to
Figure 2.6 Worm Gears
14
Bevel
system as a register control
other cylinders.
distance.
Bevel
because the
shafts.
the
rotate
the
A differential
system used on
the plate
gear color registration system used on
correction
gears.
cylinder
direct drive
A few
right-angle gearboxes use worm
The worm,
worm gear.
or special
the
threaded screw,
gear."9
round worm
assembly; the number
threads
on
the
transmission,
worm.
the
as seen as
has
which
More than
of meshed
The
as compared
gear
tooth is
the
plate cylinder on
profile, in
meshed
spur and
bevel
of
flexography
teeth
gears.
a worm and a
a cylindrical gear
order
to
together in a
mesh with
worm gear
number of
helical
provides maximum
torque
teeth is determined
meshing
include
in Figure 2.6, "is
speed reducers and as right-angle gearboxes.
propel
which
a curved side
one
multiple
to
top
gears,
by
the
Worm
Worm
presses, but
gear sets are used as
gears are never used
they
to
in
other
gear
body,
are used
flexography press applications.
Figure 2.7 Helical Gear
The helical
gear
(Figure
2.7) has
usually 45 degrees. The
teeth
engaged at
are used
common
the
types
of
angled
same
to transmit
time,
power
gearing
its teeth
teeth
machined at an angle
allow
similar
used
to
the helical gears to
to the worm
between two
propel
15
to the
have
gear system.
parallel shafts.
flexographic
They
multiple
Helical
gears
the
most
are
plate cylinders
because
of
their ability to have
more
teeth per inch than
cylinder color registration without
the fewer the
backlash,
gear
and
the fewer the
A
in improved
small amount of space
engaged and
and
the
gears
disengaged
amount of
in
backlash
a set
gear mesh
points, the
to
allow
for
The fewer the gears,
smaller
the total
amount of
teeth allows the gears to become
gear
this
set of gears
space
increases
with gear
gradually increases. One
it impossible to
wear,
or
that has excessive backlash need(s) to be replaced, because
makes
plate
color registration.
However,
backlash in any
and
mesh point contains some amount of
between meshing
easily.
gears,
additional gears.
Each
points.
meshing
backlash, which results
using
spur
both
excess
maintain accurate color register.
Figure 2.8 Anti-Backlash Spur Gears
Two types
of gears called anti-backlash gears allow a maintenance person
remove all excessive
set.
One type
of
backlashes
the
anti-backlash
whose angular position can
tooth.
The
screws on
without
the
be
having
remove or replace
gears consists of
changed so
side are
to
that there is
loosened,
16
two
and one
less
the
to
gear
narrow width gears
space
between
each
thin gear is shifted, as
indicated in Figure 2.8, to
anti-backlash gear
backlash without
remove
is the sliding
worm
the
gears.
removal of
backlash.
excessive
type,
Another type
for the
which also allows
of
removal of
Gear Materials
Flexographic
gears are made
from many different
drives the impression drum is usually
The
anilox and
iron,
fountain
although some
plate
cylinders
materials.
roller gears are
flexographers
can
be
All the gears,
made
from
usually
from
except
for the
annealed
plate cylinder
The flexographers
their plate cylinders;
however,
drive gear,
cylinder gear will wear out
that the
cylinder gear can
gears.
"Many
reduce
drive
Gear
A
be
steel or
for these
or
plastic
a
bull
The
purposes.
(composition)
by
the
of gear material
for
gears, are
the type
hardened
specified
be
softer
before the drive
gear or other
gear.
internal
prefer synthetic plate cylinder gears
than its
A
plate
machine
because
they
waves."10
Marking
subject of
this
resulting in tone
web
than
hardened teeth.
with
from
that
gear
gears vibration and shock
gear-related print
the
can select
The bull
plate cylinder gear must
replaced easier
flexographers
iron
made
steel
press manufacturers.
so
cast
use synthetic gears
made
the
materials.
direction
defect in flexographic printing is known
research.
Gear marking is
a non-uniform
variation which appears as a series of
and
bars
corresponding to the distance between
17
as gear
marking,
laydown
perpendicular
gear
of
ink
to the
teeth. It appears
prevalently in
marking is to
flexography
screens of
as
flexographic ink
problem of
discernible pattern,
What
in
solids and
gear
no
single
phenomenon
ghosting is to letterpress. It is
mechanics."11
marking is the
of
cause
induce
gear
Unlike
30-45%.
the
quintessential
that
banding
"Gear
follows
no
occurrence of a regular pattern.
gear marks.
marking.
Poorly
worn gears can cause gear marks.
which
they
helical
marks
located
are
The
In
most
made, poorly mated,
class of gears and
are a more
likely
than one
more
cases,
are more significant questions than
"Worn bearings
or spur.
substandard or
the accuracy
the
with
style of gear
mechanical cause of gear
gears."12
than are
Gear marking
occurs more
commonly in
require opaque white and
most
mid-tone range of
causes gear marking?
There is
that
the
difficult to
print.
It is
some colors than
those requiring mixing
probable
that the
in
others.
yellow and
pigments of
Matches
blue
these inks
are
the
disperse
during the transfer process or in wetting-out on the substrate.
Surface
also
speeds of
influence
marking is
the ink fountain
gear marking.
one
indication
of
The
this.
rollers relative
teardrop
Finally,
18
to
one another and
shape of
the
dots in
to the
web
screens with gear
overall mechanical soundness of
the print station is
a
factor in
gear marking.
Any looseness
in the
anilox or plate
locking mechanism can create a gear mark effect.
roll
What
Just
cures gear marking?
as
cure.
there is
"At
one
not a single cause of gear
time, doctor blades
Doctor blades
will
help
mechanical problem of
(gear mesh,
from the
(nipping)
blades
marking;
were proposed as
some causes of gear
the ink metering
bearing load,
surface speed
Numerous
samples
the
cure
for
marking
-
not a single
marks."13
gear
those
caused
by
roll and anilox roller combination
relationship) "and those resulting
wavelike phenomenon generated
process."14
therefore, there is
in the
rubber
by
the
demonstrate, however,
metering
that doctor
are not a single cure.
Helical
gears are
currently
eliminating
gear marks.
than
gears.
spur
continuing
gear
being
Helical
proposed as a significant
gears run quieter and withstand greater
"Testing, admittedly limited
marking
with
helical
gears
drive trains. Custom Tape & Label has had
in the ink drive train
with
helical
they
also experienced severe gear
gears
development in
19
Mark Andy,
throughout the ink
success
with
showed
and plate roll
in eliminating
of one station on a
marking
gears."15
at
loads
gear marks
4120. Interestingly,
improperly
meshed
helical
The
most
dealing
commonly
agent
the ink chemistry.
with
supplier's
ink
to the
pigment
successful methods of
with
ink,
another;
The
etc.
compatibility
These
eliminating
would
include substituting
re-mixing transparent
results of
these
and more uniform or
a
white; adding
changes are
better
those
gear marks are
slowing
probably
wetting-out of
one
greater
the ink.
Adding bearers to the plate also improves some gear marking.
Screen
orientation also
runs parallel
has
an effect on gear marking.
to the cylinder, the
greater
The
the likelihood that
more
the
screen
screen
is to
gear
mark.
Another
speed.
This
speeds also
and
way in
successful
better
have
a similar result
to
affect
the
altering ink chemistry for
web.
press
"Higher
slower
drying
wetting-out."16
sticky back
marking.
has been simply to increase
frequencies that
would alter resonance
Frequently, building up
marking.
some cases
with a
The
the bearer
0.005
-
0.006
composition of
Generally,
the
very
area
vinyl
behind the
tape
plate
marking.
20
plate and
will reduce or eliminate gear
the sticky back has
low-density
between
tapes
a great effect on gear
can reduce or eliminate gear
Frequently, lubrication
make some
the
of
plate roll
difference in the minimizing
sticky back thickness, altering the
diameter
of
its
driving
cylinder undercut
than
In eliminating
gear
anilox roll
If the
too
by
gear will
gear
heavily to
station, it
will
the
minimizing
anilox
not
anilox or
have
properly
plate
train
with
roll
altering
from
pitch
Frequently, "the
tendency
to
can
plate
gear mark
and
often
times removing the
allowing the impression
and
adjusted and
or
if the
the press
operator
plate cylinder
likelihood
of gear
is
is
bearing
skewed
in the
marking than the
print
adjusted.
soundness
gear marking.
rollers,
As
gear
roll will eliminate gear marking.
a much greater
mechanical
a greater
situation,
itself
to impression
is correctly
station which
Finally,
is
drive
inch."17
tinting
roll sleeve
to drive the tint
print station
a
the
same effect.
have
by 0.160
marking in
from the tint
will
roll
of gear marks.
undercut of
have the
0.164 inch
a plate cylinder undercut
drive
to impression
of
the
print
Gears, bearings,
meter rollers or
doctor blades
good condition.
21
and
station
is important in
lockup
mechanisms
and plate cylinders must
for
be in
Endnotes for Chapter Two
1. Gear. (1994). In Concise Columbia Electronic Encyclopedia
(3rd
Ed.)
[Online]. Available: http://aj.encyclopedia.com/articles/04967.html [1999,
September 9].
2.
(4th
Siconofli,
F. N.
(Ed), (1997). Flexography: Principles
Ed.). Ronkonkoma, NY: Foundation
Association,
p.
Ibid.
p.
242.
4.
Ibid.
p.
242.
5.
Ibid.
p.
242.
6.
Ibid.
p.
245.
7.
Ibid.
p.
242.
8.
Ibid.
p.
243.
9.
Ibid.
p.
243.
Flexographic Technical
p.
245.
11. Utschig, S. (1991). Gear Marking. A technical
Michael
Wiest, FTA/FFTA.
12. Ibid.
Practices.
241.
3.
10. Ibid.
of
and
p.
p.
1.
1.
22
paper
by courtesy of
13. Ibid.
p.
1.
14. Ibid.
p.
1.
15.
Ibid.
p.
2.
16.
Ibid.
p.
2.
17.
Ibid.
p.
3.
23
Chapter 3
Literature Review
Progress Report: Narrow-Web Flexographic
A
three-part
flexography Fellowship
(1996).
print
The
can
the
easily be
Sun Chemical Corporation Graduate
a
in three
was published
recipient,
article presents
defect that
Garett Long,
by
article written
Banding
author's
mistaken
on
study
for
the
volumes
of Flexo
causes and effects
gear marks
in
magazines
of banding,
narrow web
a
flexographic
printing.
Banding,
lines
also
caused
widths,
by
dot
slur
seemingly
a uniform screen
across
as
barring,
the image.
is generally described
along the
run perpendicular
occur with
in
known
length.
web
to the direction
random
tint, the
Otherwise,
as
the intermittent dark
The dark bands have varying
of web
travel
(across the web),
frequency along the web length.
slurred
each
bands
band
fairly
maintain a
can
have
a
and
When appearing
constant
different density,
density
and
the
spacing between bands is inconsistent.
The
gear
author states
marks,
a
that,
although one might
fundamental
regular pattern while
be tempted to
attribute
characteristic of gear marks
banding
follows
no
24
discernible
is the
banding to the
occurrence of a
pattern and
there is no
evidence
to
that
suggest
presence of
does
banding
advantage of
the
banding
marking falls in the
measurement of
in this
spot on
caused
variability
from true
one repeat
the
banding
that the
noted
occurrence of gear marks.
article
therefore,
as
every repeat, it has little
by banding.
long
effect
Gear marking that has
is automatically
An
for measuring the severity
one-repeat cycle patterns;
same
It is
a pitchline problem.
not preclude
method presented
is that it ignores
banding
is
weeded out with
of
as gear
on
the
a cycle of
the
author's
method.
Based
on
the author's
findings, the
characteristics of the
banding effect follow.
Banding can be produced under controlled conditions.
Bearers do
The
not
influence
shape of a screen
The tonal
According
range
to the
into
Close proximity
pitch
circle,
Low ink
Low
tint has no influence
which a screen
author's
significant reduction
in
of
which
banding severity.
findings,
on
the severity
banding.
tint falls has some influence
the
following
are
the
on
banding.
factors resulting in
a
banding severity.
the
plate cylinder pitch circle
implies least
possible gear
lash.
viscosity.
anilox cell volume.
Rough,
absorbent substrates.
Lowest
density (highly compressible)
Uncapped
of
stickyback.
plates.
25
to the impression
cylinder
Analysis
The Mechanical Phenomena Which Produce Irregularities in
of
Flexographic
This is
Printing
Flexography for
deals
the International Flexographic
a paper presented at
The
90'
s, held in
with an analysis
which produce
London, UK during
of mechanical
8th-9th
phenomena relevant
irregularities in fleography.
to
Conference:
Printing
March 1988.
article
inking or bouncing
uneven
One of the featured
The
phenomena
is
gear
marking.
Gear marking is described
at a
on
distance
the
of
cylinder and
roller
impression
there is
states
the
a
and
the
that
causes the
The
plate
slipping between
(acceleration
noticed
that the
i.e. the
following
and
variation of
cylinder
lowest
a
gear mark
is
irregularities in
is
the
contact
between
and
sinusoidal
not
its
depending
The
plate cylinders.
author
As far
a
plate
cylinder
as relative speed
diagram."1
The
period corresponds
plate
pressure, between the
relative speed variation changes
and
inking intensity
the pitch,
plate cylinder and anilox roller.
deceleration)
phenomenon
and
is due to the gearing between the
problem
A
the
on
cylinder produces gear marks.
sign
highest
of
shading
the stereos
of
anilox roller.
cyclic phenomenon,
negative
the
gear circumferential pitch or multiple of
angular position
(anonymous)
anilox
the
as
from
of course a
positive
variation
due to the slipping, but to its
an
is concerned,
"It is
to the
and
is
to
cyclic
gear pitch.
It is
variation which
printing.
proved
cylinder gears with a pair of
to disappear
friction
by
wheels.
26
replacing
anilox roller and plate
In flexographic printing,
increasing
between the
contact pressure
relative speed
between first
14
pressure angles above
Possible Causes
An Internet
the
website
of
last
gear
can reduce
Gear
Incorrect thickness
gear pitch
of
substrate or
meshing.
The
author states
that a
interference.
speed
Kevin Bott,
available at
many possible
factors
of gear
the bull gear, plate
plate, too thin
a
Flexochat member, found in
http://www.flexonet.com
causes
offlexographic gear
as
marking
on
July
marking.
follows.
cylinder gear or anilox roller gear.
could make
the
gears
bottom
out
causing
to be seen.
impression
much
with
some possible
gears on
this
by
of Flexochat Discussion Forum
Damaged
teeth
cylinder affects
Marking
correspondence contributed
Bott indicates
Too
and
the impression
30'
29th, 1999. The content deals
the
plate cylinder and
being
used
from
anilox roller
to plate
or plate
to
both.
Using too soft a plate and/or cushion back tape.
Bull,
plate,
running
anilox gears are not
out
from
The
substrate
and
causing
side
to
Incorrect setting
maybe one of
the
gears
is
side.
may be very
gear
meshing properly;
thin in
caliper
causing
extra
impression to be
used
bottoming.
of
the
reverse
angle
judder.
27
doctor blade
system
causing blade
The direct
circuit
drive
of
the machine
may be
checked with an oscilloscope connected to
incorrectly;
set
the drive itself
or
by
this
the
can
be
use or a
stroboscope on the gears.
Ink
density
inevitable
Cylinder
be
may be weak, causing too
gear
impression to be
used and
the
bottoming.
runout or
total indicated
runout
(TIR) causing
more
impression to
used.
Incorrect
selection of anilox cell counts;
impression to
achieve the required solid
The Beginner Flexographer:
Your Press
An
much
cell
counting
cause more
density.
Everyday Printing Problems
and
How to
Keep
Running
article written
Inc., appearing in
problems
too fine
by Joseph Michals,
the
1985 issue
May
that flexography
a
Technical Service Representative, Mark Andy,
ofFlexo magazine
discusses
a
group of printing
press operators might encounter on a regular
basis, including
gear marks.
Michaels
states
that the printing
three different factors
marks, Michals
1)
problems are
set -up,
2)
usually
mechanical,
and
caused
3)
ink.
by
one or all of
Speaking of gear
states that:
"These [gear marks]
a)
Gears
are parallel
bottoming out
28
lines
of
misprint;
they are caused by:
b)
Erratic
c)
Improper formulation
the
movement of
of
web
the ink
Generally a thick ink should be
Pros
and
This is
Cons
of
an article
contributed
Doctor Blades
article points out some
apply to the
of the
narrow web printer
advantages and
of
the
one of
is the
marks."3
of
the
disadvantages of use of doctor blades
advantages of
this type
doctor blades
elimination of gear marks.
anilox gear and
source of gear
possibility
Director of Gar-Doc, Inc. in 1978.
Managing
Since the
the
effect of
of gear mark
is
the
second part
of
article
plastics.
as
they
rubber roller
deals
with
an article appeared
printing
Gear marking is
they apply
marks caused
big a problem
is
to the
as
eliminated also
by
any
the
eliminated.
Journal of the Plastics (December, 1978)
This
as
"Gear
rubber roll gear are as
Trouble-Shooting in Flexographic Printing of Plastics
This is the
The
narrow web flexography.
Gartner indicates that
interaction
the Narrow Web Printer
found in the Flexographic Technical Journal (March-April, 1978)
Gerald J. Gartner,
by
on
used."2
by
problems
(Part Two)
in the Plastic Southern Africa: Official
Peter J.
Chadwick, Cobden Chadwick Ltd.
due to the inks in flexographic printing of
also mentioned under
29
the
heading
"Gear tooth
marking".
Speaking
of gear
that, "If the
the
gear
ma'rking in flexographic printing
print shows
tooth,
in
light/heavy
then the gear is
one
colour
dried ink
either
by
cutting the
job, by using
or other
contary
the impression
plastics, Chadwick states
marking repeating
'bottoming'."4
more obvious on presses with spur gears
solved either
of
The
than
problem
with
helical
plate cylinder gear teeth a
an extra
matter
layer
with
roller or plate cylinder
30
is
in the bottom
also
the
frequency
said
to be
gears and
little deeper,
of stickyback under
being trapped
is
the
the
of
plate.
the
gear
of
much
is easily
or
for
a
A bit
of
tooth
of
cause of gear marks.
Endnotes for Chapter Three
1. Anonymous.
(1988, March). Analysis of the
Mechanical Phenomena
Which Produce Irregularities in Flexographic Printing. Paper
International Flexographic
2.
Problems
3.
Printing Conference, London,
presented at
the
United Kingdom,
p.
Michals, J. (1985, May). The Beginner Flexographer: Everyday printing
and
How to
Keep Your Press Running.
Gartner, J. G. (1978). Pros
and
Cons
of
Flexo, 10, 95.
Doctor Blades
on
the Narrow
Web Printer. Flexographic Technical Tournal, 3, 5.
4.
2.
Chadwick, P. J. (1978). Trouble-Shooting in Flexographic Printing of
Plastics. Plastics Southern Africa: Official Tournal
31
of
the Plastics, 8, 41.
Chapter 4
Hypotheses
The
objective of
were
the
studied
image
The
included
plate
substrate
alternative
and surface speed
the
several
factors that
that were
differential between the
research was
to find
out
plate
follows:
differential between the
parameters and combination
plate
image,
with each other
and
the
influence
marking?
this
research
hypotheses (Hj),
no significant
different levels
some of
marking in flexography. The factors
and surface speed
individual
answer
H01: There is
that this
hardness,
as
to
hardness,
to investigate
the substrate.
flexographic gear
two
plate
major question
order
research was
possible causes of gear
area and
How do
In
this
of plate
question, two
were stated
difference in
hardness.
32
null
hypotheses (H0),
as well as
below.
gear mark
severity
printed with
three
Hn: There is
different levels
H02: There is
difference in
a significant
of plate
gear mark
severity
printed with
three
harndess.
no significant
differential between the
difference in
gear mark
surface speed of plate
severity
image
when
area and
comparing the
the
surface speed
of substrate.
H12: There is
a significant
differential between the
difference in
gear mark
surface speed of plate
of substrate.
33
severity
image
when
area and
comparing the
the surface
speed
Chapter 5
Methodology
The
objective of
to be the causes
studied
plate
was
How do
plate
is
hardness,
stated as
hardness,
the substrate
as
to investigate
the
and
the
factors that
printing.
surface speed
The
were expected
The factors that
were
differential between the
that this
research
differential between the plate image
area and
substrate.
major question
follows:
and surface speed
individual
the severity offlexographic
some
marking in flexographic
surface area and
answer
plate
research was
of gear
included
image
to
this
parameters and combination with each other
influence
gear marking?
Methodology
1.
The test image
Since
was
digitally prepared
gear marks were expected
range of screens of magenta,
square
inch tint blocks
of
Between two tint blocks
40
are
with
to be the
the Adobe Illustrator application.
most noticeable
the test image
was
designed to
percent of magenta on
0.5-point horizontal
34
in the
both
lines,
contain
sides of
with
mid-tone
the
0.5-point
two
page.
spaces
between lines running
during the pressruns.
across
the
web
length to
The test target image
if.
was
monitor
the plate
flowing
depicted in Figure 5.1.
:*-'
If
,_
m
Figure 5.1 Test Target (55
2. The
filmmaking
Technology's
process
(RIT's)
was
percent
of the
performed
at
Electronic Prepress &
35
actual print size)
the Rochester Institute
Publishing
Laboratory.
of
The
Illustrator target file
imported to
a
3.
film for
and
of
for
Conventional
Angle
45 degree
and pressrun were performed at
pressruns were performed on
two-roll
700
inking
lpi, 2.5
the
output are as
follows.
inch)
inch)
the RIT's
the Mark
Flexography
Andy 4120
system equipped with a
System
doctor blade,
BCM (Billion Cubic Micron).
Plates
to
were
obtain
40 Shore A (Cyrel UXL), 50 Shore A (Cyrel HL),
The ASTM D 2240
low
produce a
uncapped photopolymer plate materials
hardness
all
per
per
Halftoning
durometer hardness. Since
standard
for the film
133 lpi (lines
anilox of
on papers with
settings
Ruling
then
and
From the QuarkXPress document,
Screen
60 Shore A (Flex-Light FL-1).
Appendix A.
Illustrator EPS format
2400 dpi (dots
three 0.067-inch
three levels
an
Resolution
narrow-web press:
made of
The
platemaking.
Laboratory. The
Haper's
as
to the Agfa Select 5000 imagesetter to
was sent
The platemaking
with a
saved
QuarkXPress document.
the image file
negative
was
Platemaking
was used as
standards are shown
the
standard
gear marks were expected
test
in the
method
to be easily
observed
surface absorbency, a gloss coated paper stock was
pressruns.
Akzo Nobel's
for
water-based magenta
ink
the
was
used.
4.
To test the
of
effect of plate
hardness
hardness,
three plate materials made
40 Shore A, 50 Shore A,
36
and
60 Shore A,
of
three levels
were compared.
Plates
the
were run on
same
type
of
the
the
plate cylinders with
same
printing conditions.
5.
To study the
effect of
mounted on
two stickyback thickness
medium
density 1020),
density 1015)
tachometer
run at
differential,
0.015 inch (3M
100 feet
to measure the surface
experiment consisted of six pressruns.
the
use
of
three different
hardness
Thirty press
designated
For
a
speed
time,
(100 feet per
and
for the data
dot
indices
and
The
were of
the
all
of
the 0.020-inch
use of
three different
stickybacks.
Verity IA,
software measured
the
press ran at
scanner and
the
available at
the
defect indices
the RIT's
mottle,
bars; only horizontal bar defect indices
Twenty
the regions
area were selected and scanned.
output
pressruns were of
on
mounted
analysis of gear mark severity.
the
A
pressrun.
minute).
horizontal
were placed on
percent
(fpm) for every
The first three
evaluation, software called
was used.
streaks,
collected
the 0.015-inch
The
during the pressruns.
speeds.
hardness
three pressruns
cushion-mount plus
sheets of each pressrun were collected when
Center,
vertical
other
mounted on
quantitative
T&E
the
and
plate
was
cushion-mount plus medium
speed variation
per minute
durometer
each plate
0.020 inch (3M
The
plate
8.
to
was used
stickybacks,
7.
and
speed
to create the surface
press was set
6.
the surface
readings
37
The
of
samples,
interest
(ROI)
software read
were
one at
of
40
the defect
to Microsoft Excel spreadsheets
In general, the lower the defect index
automatically.
value
the less the
gear
mark severity.
9. For
visual
pressrun.
only 40
30
evaluation,
Each
percent
press sheet was cut
dots
of magenta.
to
severity.
Each
of each
pressrun,
and a
written
instructions.
"Please visually
and
F, in
least
noticeable
certain
A copy
in
gear
copy
the
six
(6)
six pressruns
press
prints suffer from gear
to disregard any
and
other print
of visual analysis
visual evaluation
from
of visual analysis
marking
10. For data analyses, the
done
evaluation was
from
by
a
group
in terms
6
being
defects.
test form is
also
psychometric
analysis,
and
statistical method was applied
test form with the
sheets, labeled as
the
most noticeable
of gear
following
A, B, C, D, E,
with
in
one
1
being
the
gear marking.
included in Appendix B.
ranking technique
of
was used
Variance
quantitative analysis.
38
6
of
"
the two-factor Analysis
to the
1-
marking from
each
containing
observer was provided six sample press sheet
examine and rank
terms of how the
chosen
randomly
obtain a piece of sample
Visual
observers who ranked the samples
marking
Be
one press sheet was
for the
(ANOVA)
Equipment
Test Target Design
PowerMacintosh 8600
computer
Iomega 100 MB zip disk
QuarkXPress 4.0
Illustrator 8.0
application
application
Filmmaking
Agfa Select 5000 imagesetter
Platemaking
Sheet Photopolymer printing
HL,
and
plates
(0.067 inch thick): Cyrel UXL, Cyrel
Flex-Light FL-1
Cyrel 3040 Exposure/ Dryer
Cyrel 3040 Processor
unit
unit
Cyrel Finish/Post Exposure
unit
Pressrun
Mark
Andy 4120 System narrow web press
Haper
anilox
Akzo Nobel
Coated
roller, 700
lpi,
2.5 BCM
magenta water-based
ink
paper stock
3M Cushion-Mount Plus Medium
1020 (20
mil
thickness)
stickybacks
Miscellaneous
Shore A Durometer
Tachometer
39
Density
1015 (15
mil
thickness),
and
Evaluation
Verity LA application software
Compaq Deskpro computer
Agfa Duoscan
scanner
Microsoft Excel 98
Microsoft Word 98
application
application
40
Chapter 6
Results
The
original scope of
hardness
this
project was
to investigate the
differential between the
and surface speed
flexographic
gear marking.
research was
to find
stated as
How do
hardness,
substrate,
the
on
plate
substrate
as
out
individual
were
narrow-web press.
60 Shore
image
A,
severity
was
the
plate
two
image
factors; plate
area and
major question
the
that the
differential between the
plate
image
parameters and combination with each other
area and
influence
gear marking?
designed
and printed on
Three levels
and variation
area and
Thus,
effect of
follows:
and surface speed
the severity offlexographic
The test target
is
Analyses
and
in the
the substrate,
the dependent
of plate
the RIT's Mark
differentials between the
independent
variable of
the
41
System
hardness; 40 Shore A, 50 Shore A,
surface speed
were
Andy 4120
study.
variables while gear
and
plate
marking
A group
of
thirty
observers at
the Rochester Institute
to participate in press sheet visual evaluation
in terms
The
of gear mark severity.
horizontal bar defect indices for the
Surface Speeds Measured
The
surface speeds
with
Verity IA
of
Technology
by ranking six sample
software was used
to
were asked
press sheets
measure
the
quantitative analysis of gear mark severity.
the Tachometer
(average) measured
with
the tachometer are
shown
in Table
6.1.
Table 6. 1 Surface Speed (Average) Measured
with
the Tachometer
Average Surface Speed
1020 Stickyback
(feet/minute)
1015 Stickyback (15 mil)
(20 mil)
Plate Image
Substrate
Differentials
Plate Image
Substrate
Differentials
40 Shore A Plate
106.54
107.29
0.75
106.00
106.50
0.50
50 Shore A Plate
107.66
106.29
1.37
106.80
106.84
0.04
60 Shore A Plate
107.80
106.53
1.27
107.38
107.43
0.05
The tachometer
the
plate
those
image
run with
readings indicated
and
the
the 1015
that the
substrate run with
surface speed
the 1020
differentials between
stickybacks were
higher than
stickybacks.
Quantitative Analysis
When comparing the horizontal bar defect indices among
sheets; based
that
on
the two-factor Analysis
was performed and shown
of
Variance
in Table 6.2., the
42
six sample press
(ANOVA)
statistical method
following was found:
Table 6. 2 Two-Factor ANOVA
Variation
Degree
Summary Table
Sum
of
of
Mean Square
Squares
Calculated
Critical
F Ratio
F Ratio
4.79
Freedom
Plate Hardness
2
29115.66
14557.83
1196.96
Surface Speed Differentials
1
2075.97
2075.97
170.69
6.85
13.29
4.79
Interactions
In
order
mark
Total
for
rows
1196.96,
323.34
161.67
120
1459.48
12.16
125
31862.93
2
a significant
severity to
among
was
Error
difference for the
occur at a
had to be
at
99%
confidence
least 4.79.
the plate hardness on
effect of
level,
gear
the F-value for the difference
The F-value for the difference among
therefore the difference among three levels
of plate
rows
hardness is
significant.
In
order
for
between the
a
99%
at
a significant
plate
confidence
least 6.85.
image
level,
difference for the
area and
the
order
factors
for
a significant
on gear mark
cells was
cells
occur at a
had to be
at
effect of
99%
therefore the interaction
significant.
43
interaction
confidence
least 4.79.
columns
columns was
the
differentials
severity to
differentials is
surface speed
difference for the
severity to
13.29,
surface speed
substrate on gear mark
The F-value for the difference between
the difference among
among
the
the F-value for the difference between
therefore the difference between the
In
effect of
level,
occur at
had to be
170.69,
significant.
between two
the F-value for
The F-value for the difference
between two factors is
Visual Analysis
The
psychometric
technique
was used
interval data (Gaussian abscissae),
interval
scale as shown
Table 6.3
to transform the
which were
then
ordinal ranks
averaged
to
construct
in the Table 6.3.
Gaussian Abscissae, Interval Scale,
and
Standard Errors
Observer
A
B
c
D
E
F
-1.3830
l
-0.2104
0.6745
-0.6745
0.2104
1.3830
2
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
3
0.2104
0.6745
-1.3830
-0.6745
1.3830
-0.2104
4
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
5
-0.2104
0.6745
-0.6745
0.2104
1.3830
-1.3830
6
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
7
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
8
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
9
-0.2104
0.6745
-0.6745
0.2104
1.3830
-1.3830
10
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
11
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
12
-0.2104
-1.3830
0.2104
0.6745
1.3830
-0.6745
13
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
14
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
15
-0.2104
0.6745
-0.6745
0.2104
1.3830
-1.3830
16
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
17
-0.2104
0.6745
-0.6745
0.2104
1.3830
-1.3830
18
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
19
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
20
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
21
-0.2104
0.6745
-0.6745
0.2104
1.3830
-1.3830
22
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
23
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
24
-0.2104
0.6745
-0.6745
0.2104
1.3830
-1.3830
25
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
26
0.6745
-1.3830
0.2104
1.3830
-0.6745
-0.2104
27
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
28
-0.2104
0.6745
-0.6745
0.2104
1.3830
-1.3830
29
-0.2104
0.6745
-0.6745
0.2104
1.3830
-1.3830
30
-0.6745
0.6745
-0.2104
0.2104
1.3830
-1.3830
Average
-0.4453
0.5373
-0.3607
0.2355
1.3144
-1.2812
Standard Deviation
0.3256
0.5132
0.3157
0.2801
0.3693
0.3131
Interval Scale
0.84
1.82
0.92
1.52
2.60
0.00
44
into the
the
According to the Table 6.3:
A
was
the
B
was
the
press sheet printed with
the 60 Shore A
plate and
1020 stickyback,
C
was
the
press sheet printed with
the 50 Shore A
plate and
1020 stickyback,
D
was
the
press sheet printed with
the 50 Shore A
plate and
1015 stickyback,
E
was
the
press sheet printed with
the 60 Shore A
plate and
1015 stickyback,
F
was
the
press sheet printed with
the 40 Shore A
plate and
1020
Upon
press sheet printed with
inspecting the
interval
scale
sample press sheets were ranked
in
gear
marking in the
the 40 Shore A
data
as shown
from the
plate and
in Table 6.3, it
most noticeable
F, A, C, D, B,
following order;
45
1015 stickyback,
stickyback.
appears
to the least
and
E.
and
that the
noticeable
Chapter 7
Conclusions
The
original
H01: There
two
will
pairs of
be
no significant
three different levels
H1:l: There
will
be
will
of plate
be
of plate
no
research were:
difference in
gear mark
severity
printed with
hardness.
a significant
three different levels
H02: There
hypotheses for this
difference in
gear mark
severity
printed with
hardness.
significant
comparing the differentials between
difference in
plate
image
gear
mark
severity
surface speed and
when
the substrate
surface speed.
H12: There
will
be
a significant
the differentials between
difference in
plate
image
gear mark
severity
surface speed and
speed.
46
when
comparing
the substrate surface
Based
on
the results, H01was rejected
difference in
significant
gear mark
plate
hardness.
plate
hardness levels, the
According
hardness
A
gear mark
plate
image
in
and
gear
H12
area
evaluation, between two
1020
that lower
than a higher one.
comparing
substrate.
According
surface speed
Since the 1020
a conclusion can
plate
be
will produce more noticeable
image
in
gear
to the
differentials,
in
the
gear
stickybacks created
area and
made that a
was a
surface speed
stickybacks were more noticeable
differentials between the
than the 1015 stickybacks,
made
accepted, as there
was
the
and
then be
marking
when
severity
than those printed 1015 stickybacks.
speed
printed with
conclusion can
the results, H02was rejected
sample press sheets printed with
surface
when
will produce more noticeable
more surface speed
among three
the
plate
marking
evaluation,
were
gear marking.
visual
visual
60 Shore A
in
the
the
those
noticeable
analysis of
of
of
the
least
differentials between
three different levels
printed with
a
were
marking,
difference in
accepted, as there was
was
40 Shore A
gear
significant
Hn
sample press sheets printed with
in
on
severity
to the analysis
most noticeable
Based
and
the substrate,
higher differential in
marking than
a
lower
differential.
The findings
also
indicated that there
the interaction between two factors
was a significant
on
the
47
difference for the
gear mark severity.
effect of
Recommendations for Further Investigation
A further investigation
might attribute
questions
that
a
to
can
be
performed to
gear mark
further study
study
some of
severity in flexography.
would answer
How do ink viscosity, ink pH,
and
the
other
Some
of
factors that
the
possible
include:
ink type (water ink
vs.
UV cure)
affect
the
severity of gear marking in flexography?
How do
anilox cell
volume,
and anilox
line
screen affect
the severity of
gear
marking in flexography?
Also, besides horizontal bar defect indices which
can
be
obtained
by means of
Verity IA software readings, defect indices of some of the other print defects,
such as vertical streaks and
beneficial to investigate
defects
It
with
the
would also
marking,
be
use of
to the
some
can also
be
obtained.
printing factors that
It
would
can contribute
then
be
to those
print
Verity IA software to evaluation the print defect severity.
interesting to study relationships among print defects, gear
vertical
streaking, and
Although the study
greater
mottle,
can
understanding
be
mottling
considered
and a
higher
with
the
use of
Verity IA software.
exploratory in nature, it is hoped that
awareness of
flexography industry at larger.
48
the
problem will
be
a
conveyed
Appendices
51
Appendix A
Platemaking Standards
52
Appendix A
Platemaking Standards
Table A
1
Platemaking Standards
Post
Finish
Drying1
Exposure
Exposure
(minutes)
(hour)
(minutes)
(minutes)
15
7
1
10
14
28
10
7
1
10
14
28
20
7
1
10
14
Back
Main
Plate Material
Exposure
Exposure
Processing
(0.067 inch)
(minutes)
(minutes)
Cyrel UXL
41
Cyrel HL
Flex-Light FL-1
Drying Temperature
130 F
53
Appendix B
Visual Analysis Test Form
54
Wisit Wirojrungson: Thesis Observations
Date
Instructions:
Please visually
and
F, in terms
examine and rank
of
how the
the
six
prints suffer
(6) press sheets, labeled
from
gear
marking from
as
1-
A, B, C, D, E,
6
with
1
being the least noticeable in gear marking and 6 being the most noticeable in
gear marking.
Be
certain
to disregard any
other print
defects.
A
B
C
D
E
F
Thank
you for your participation.
55
Appendix C
Data
and
Statistics
56
Appendix C
Data
and
Statistics
Quantitative Analysis
Table B Horizontal Bar Defect Indices
UXL1015
Average
UXL1020
HL1015
HL1020
FL1015
FL1020
50.0
53.6
10.2
19.7
11.7
15.9
39.5
53.6
11.8
18.1
11.6
17.4
35.6
47.6
12.1
19.7
5.4
13.2
47.3
48.2
11.9
21.9
13.3
16.5
49.6
52.9 L
14.9
16.9
12.7
17.4
32.5
50.8
10.9
21.8
4.4
13.1
47.8
49.0
14.1
22.4
10.7
12.8
38.2
59.5
14.0
15.1
10.1
20.5
46.6
46.9
12.6
19.5
6.1
19.2
42.9
53.4
12.0
19.9
10.2
20.0
38.0
60.5
16.8
16.3
13.8
12.8
37.9
52.4
14.0
20.4
8.5
19.7
41.6
48.7
11.0
20.0
9.6
16.6
38.7
61.8
16.2
17.0
13.3
22.6
33.2
53.1
9.8
20.3
12.1
19.6
42.0
53.9
13.0
15.5
8.2
16.1
42.4
56.5
15.6
18.2
16.0
20.0
35.5
56.2
13.9
18.2
14.1
19.8
43.7
51.1
11.8
15.7
7.5
11.3
37.2
57.7
17.6
17.9
15.1
17.1
37.9
56.2
14.7
17.2
12.4
18.3
57
Table C ANOVA for Horizontal Bar Defect Indices
Variation
Degree
of
Sum
of
Squares
Mean Square
Calculated
Critical
F Ratio
F Ratio
4.79
Freedom
Plate Hardness
2
29115.66
14557.83
1196.96
Surface Speed Differentials
1
2075.97
2075.97
170.69
6.85
Interactions
2
323.34
161.67
13.29
4.79
Error
120
1459.48
12.16
Total
125
31862.93
Visual Analysis
Table D Visual Evaluation
by A Group of Observers
Observer
A
B
C
D
E
F
1
4
2
5
3
1
6
2
5
2
4
3
1
6
3
4
3
2
6
5
1
4
5
2
4
3
1
6
5
6
7
4
2
5
3
1
6
5
2
4
3
1
6
5
2
4
3
1
6
8
5
2
4
3
1
6
9
4
2
5
3
1
6
10
5
2
4
3
1
6
11
5
2
4
3
1
6
12
4
6
3
2
1
5
13
5
2
4
3
1
6
14
5
2
4
3
1
6
15
4
2
3
1
6
16
5
2
5
4
3
1
6
17
4
2
5
3
1
6
18
5
2
4
3
1
6
19
2
4
3
1
6
20
5
5
2
4
3
1
6
21
4
2
5
3
1
6
22
5
2
4
3
1
6
23
5
2
4
3
1
6
24
4
2
5
3
1
6
25
5
2
2
4
1
6
6
3
3
1
5
4
26
27
5
2
4
3
1
6
28
4
2
5
3
1
6
29
4
2
3
1
6
30
Sum of Ranks
5
2
5
4
3
1
6
135
68
129
89
34
175
Squared
18225
4624
16641
7921
1156
30625
Total
79192
58
When:
A
was
the
press sheet printed with
the 40 Shore A
plate and
1015 stickyback,
B
was
the
press sheet printed with
the 60 Shore A
plate and
1020 stickyback,
C
was
the
press sheet printed with
the 50 Shore A
plate and
1020 stickyback,
D
was
the
press sheet printed with
the 50 Shore A
plate and
1015 stickyback,
E
was
the
press sheet printed with
the 60 Shore A
plate and
1015 stickyback,
F
was
the
press sheet printed with
the 40 Shore A
plate and
1020
Outline
1.
of
the Psychometric Technique
Observers
order of
2.
The
were presented with all
how the
prints suffered
from
ranks were examined against
stickyback.
The Method
the stimuli,
and
of
and asked
Ranks
to
rank
them in
gear marking.
the hypothesis that
they were
assigned at
random.
3.
The
ranks were converted
turn,
4.
converted
The Gaussian
to
to Gaussian
cumulative
probabilities, which were
then, in
abscissae.
abscissae were averaged across observers
Scale.
59
to
yield
the Interval