FTA (изд-во). Flexography: Principles And Practices. Vol.1-6
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PRESSROOM PRACTICES 227
FILL-IN
FOAMING
GEAR MARKS
GHOSTING
HALO
1. Excessive pressure settings.
2. Plate cupping.
3. Plate durometer too hard.
4. Stickyback too thin or too firm.
5. Plate cylinder running out of round.
6. Excessive plate grinding.
1. Use minimum pressure settings for
plate and anilox.
2. Make new plates and new plate
matrix or engraving. Avoid cupping.
3. Use recommended plate durometer
for printing given materials.
4. Use compressible stickyback.
5. Check plate cylinder for T.I.R.
6. Reduce amount of plate grinding.
■ An unwanted line
surrounding a
printed image.
■ Printed image
appears double-
edged.
1. Ink starvation.
2. Improperly cleaned metering roll.
1. Change diameter of plate cylinder or
change speed differential of fountain
roll to anilox roll. Change anilox roll
specification to a higher volume.
Increase ink flow to chambered
doctor blade.
2. Thoroughly clean anilox and/or
fountain roll.
■ A faint image of
design transferring
to the printed image
or non-image area.
1. Gear bottoming off pitch line. 1. Adjust overall plate package thick-
ness to pitch line.
■ Parallel lines of
misprint.
1. Excessive agitation of ink in fountain.
2. Lack of defoaming agent in
formulation.
3. Contaminated ink.
4. Excessive ink viscosity.
1. Reduce flow rate of ink pump.
2. Add defoaming agent to ink.
3. Replace with fresh ink.
4. Reduce ink viscosity.
■ Ink foams in
fountain.
1. Excessively fine type or screen for
anilox roll selection.
2. Excessive pressure settings.
3. Uncontrolled ink viscosity and/or pH
range.
4. Improperly set ink metering
applications.
5. Incorrect solvent balance.
6. Excessively sized particles of ink
pigment.
7. Lack of relief height in plate.
8. Low fountain roll durometer.
1. Select higher line, screen lower
volume anilox roll.
2. Use minimum pressure settings for
plate and anilox.
3. Maintain proper ink viscosity and/or
pH range. Use fountain covers.
4. Increase pressure settings of
fountain roll nip or doctor-blade
assembly.
5. Use correct solvent balance.
6. Improve grind and pigment
dispersion.
7. Increase relief height in plate.
8. Use higher durometer roll.
■ An accumulation of
excess ink on and
around the printing
plate surface —
especially with rela-
tion to small type
and screen
halftones.
DEFECT/INDICATOR PROBABLE CAUSE CORRECTIVE ACTION
PRESSROOM TROUBLESHOOTING CHART
(CONT‘D)
228 FLEXOGRAPHY: PRINCIPLES & PRACTICES
HICKEYS
INK MOTTLING
MISREGISTER
1. Plates not mounted in register.
2. Incorrect web tension.
3. Incorrect drive-roller adjustment.
4. Excessive web temperatures.
5. Failure to center press register
compensators before putting job in
press.
6. Idle rolls dragging or running
intermittently.
7. Press out of alignment.
8. Gauge variations in substrate.
1. Remount plate in register.
Review plate mounting and make-
ready procedures.
2. Adjust tension controls appropriately
for substrate being printed.
3. Check drive roll parallel for constant
side-to-side pressure and center
wear condition.
4. Reduce dryer temperatures.
5. Center individual advance/retard run-
ning registers and side-to-side regis-
ter compensators before manually
keying in job register.
6. Replace or lubricate idle roller
bearings.
7. Realign press.
8. Replace substrate.
■ One part of design
not correctly posi-
tioned with another.
1. Excessive reduction of ink viscosity
and/or pH level.
2. Excessive anilox roll cell land areas.
3. Contaminated ink.
4. Mottled pattern in surface of plates.
5. Foreign matter collecting on surface
of plates.
6. Dirty or pitted impression cylinders.
7. Uneven or irregular substrate
surfaces.
8. Ink lacks proper flow characteristics.
1. Add fresh ink and maintain optimum
viscosity and/or pH range.
2. Examine condition of anilox roll cell
lands. Replace anilox roll if necessary.
3. Replace with fresh ink.
4. Remake plates if mottled appearance
is evident on surface. Examine plate
mold for like pattern of mottle.
5. Wash plates thoroughly.
6. Clean impression cylinders thorough-
ly of inks, waxes and all other foreign
matter.
7. Increase opacity of the ink. Reduce
durometer of plate material.
8. Consult ink supplier for
reformulation.
■ Spotted or irregular
appearance of solid
print area.
1. Dust on the substrate transferring to
the plate.
2. Excessive ink tack.
1. Wash plate, use web cleaning/static
eliminator devices if necessary.
2. Reduce ink tack level.
■ A small, solid print
area encircled with
a white halo.
DEFECT/INDICATOR PROBABLE CAUSE CORRECTIVE ACTION
PRESSROOM TROUBLESHOOTING CHART
(CONT‘D)
PRESSROOM PRACTICES 229
MOIRÉ
ODOR
OFFSETTING OR SET-OFF
PICK-OFF/INK
1. Ink drying too slow.
2. Excessive plate impression setting.
1. See defect “Drying Too Slow.”
Increase between station dryer tem-
perature and/or air flow.
2. Use minimum plate impression
pressure.
■ Ink transferring to
subsequent plates
and rollers.
1. Ink not dry at rewind or stacker.
2. Trapped solvents or amines.
3. Excessive pressure in roll.
4. Excessive weight in stack.
5. Films treated on both sides.
6. Films with plasticizers subject to
migration.
1. See defect “Drying Too Slow.”
2. Reduce ink film to minimum accept-
able thickness.
3. Reduce rewind tension.
4. Reduce height in stack.
5. Run minimum rewind tension. Apply
offset powder to web before rewind-
ing. Overprint with non-blocking var-
nish if necessary.
6. See No. 5.
■ A transfer of ink
to the side of the
substrate opposite
where it was
printed.
1. Retained solvents, amines or
monomers.
1. Balance solvents and check for prop-
er solvent use. Use correct UV ink
chemistry. Check and adjust main
dryer/UV lamp operation. Increase
between station dryers/UV lamps.
Reduce press speed to increase
dryer/UV lamp dwell time.
■ Undesirable odor in
printed substrate.
1. Improper screen angles.
2. Anilox screen count too similar to
plate screen count. For example, a
165 line anilox used with an 85 line
screen plate can cause moiré
because of harmonic 85 x 2 = 170,
too close to 165 line.
1. Screen angles of each color should
be 30° apart. The yellow should be
15° between two colors, in most
cases the cyan and black. Actual
angles are based on imagesetter des-
ignated screening, providing the
nominal screening rule is placed at
least 7.5° away from the anilox
screen angle.
2. Select an anilox screen count of at
least three to four times the plate line
screen count.
■ Undesirable inter-
ference pattern in
process printing.
DEFECT/INDICATOR PROBABLE CAUSE CORRECTIVE ACTION
PRESSROOM TROUBLESHOOTING CHART
(CONT‘D)
230 FLEXOGRAPHY: PRINCIPLES & PRACTICES
PINHOLING
PLATE SWELLING
POOR INK TRANSFER
SEPARATION OR KICK-OUT, INK
1. Presence of wrong solvent or excess
diluting agent..
1. Add rich true solvent to return ink to
proper balance.
■ Curdling and
thixotropic (similar
to souring).
1. Ink viscosity excessively reduced.
2. Plugged anilox roll.
3. Ink drying on plates.
4. Surface of substrate pitted or
not ink receptive.
5. Improper pressure setting between
fountain roll, anilox roll and plate.
1. Rebuild tack and color strength by
addition of fresh ink or extender – or
both.
2. Thoroughly clean anilox roll.
3. See defect “Drying Too Fast.”
Reduce drying rate with slower
solvent.
4. Verify ink formulation with ink suppli-
er for given substrate. Add anti-pin-
hole compound. Check substrate for
appropriate treatment level. Increase
plate impression setting to the sub-
strate.
5. Adjust pressure settings.
■ Insufficient ink
being applied to
substrate.
1. Inks or solvents not compatible with
printing plates.
2. Residual solvent left in plate from
processing.
1. Check inks and solvents being used
for compatibility with your ink and
plate suppliers.
2. Increase plate processing drying
time.
■ Plate dimensionally
larger and softer.
1. Physical surface of substrate is pit-
ted, irregular or contaminated.
2. Failure of ink to form continuous
film.
3. Ink drying too fast.
4. Excessive land areas on anilox roll.
5. Anilox roll cell engraving angle.
6. Dirt on impression cylinder.
1. Consult your material supplier.
2. Increase ink film thickness. Increase
plate impression pressure to sub-
strate. Add 2% to 3% anti-pinhole
compound to ink. Check substrate
for the appropriate treatment level.
3. Use slower solvent or increase press
speed.
4. Examine condition of anilox land
areas. Replace anilox roll if necessary.
5. Specify 60° anilox roll engraving
angle.
6. Clean impression cylinders.
■ Small holes in solid
print area.
DEFECT/INDICATOR PROBABLE CAUSE CORRECTIVE ACTION
PRESSROOM TROUBLESHOOTING CHART
(CONT‘D)
PRESSROOM PRACTICES 231
SKIPPING PRINT
SOURING INK
STREAKS, SMEARS OR SPOTS
STREAKS IN WEB DIRECTION
STRIATIONS
1. Excessive ink transparency.
2. Excessive ink viscosity reduction.
3. Plugged anilox roll.
4. Worn anilox roll.
1. Reformulate for greater opacity level.
2. Replace or add fresh ink.
3. Clean anilox roll.
4. Replace anilox roll.
■ Parallel thin lines or
bands present in
solid print areas.
1. Damaged fountain or anilox roll.
2. Nick in doctor blade.
1. Replace or refinish metering rollers
depending on extent of damage.
2. Hone or replace doctor blade.
■ Continuous dark
lines through print.
1. Undissolved particles in ink.
2. Ink dripping onto web or sheet.
3. Ink throwing off anilox roll.
4. Ink not drying properly.
5. Excessive foaming.
6. Contact with the ink film and sub-
strate.
1. Filter particles out of ink, clean up
plates and anilox.
2. Check print station ink application
and circulation system for overflow
or leaks.
3. Increase ink viscosity. Replace end
seals or wipers.
4. See defect “Drying Too Slow.”
5. Add anti-foam to ink.
6. Remove any objects contacting the
ink film and substrate.
■ Unwanted ink
transfer on web or
sheet.
1. Excessive moisture in ink due to high
humidity levels.
1. Add normal propyl acetate. Keep
fountains and reservoirs covered.
■ Ink exhibits a
thixotropic state
with a loss of flow
and tendency to
curdle.
1. Inconsistent plate caliper.
2. Impression settings too light.
3. Plate cylinder bounce.
4. Failure to lock down print station.
5. Print station cocked or out of
parallel.
1. Check plate caliper for a variation of
greater than ± 0.001". Secure new
plates or do necessary makeready.
2. Increase impression settings for
plate and/or anilox.
3. Check T.I.R. of plate cylinder and
impression cylinder. Observe the
condition of shafts, journals, bear-
ings and gears for cleanliness or
excessive wear. Consider nature of
artwork design.
4. Be sure printing stations are locked
firmly in place when impression is
properly set.
5. Reset print station for side-to-side
parallel.
■ Voids in print
image area.
DEFECT/INDICATOR PROBABLE CAUSE CORRECTIVE ACTION
PRESSROOM TROUBLESHOOTING CHART
(CONT‘D)
232 FLEXOGRAPHY: PRINCIPLES & PRACTICES
WEB WEAVE
WRINKLING
1. Baggy substrate.
2. Equipment misalignment.
1. Tape rollers at web edge to draw out
wrinkles.
2. Adjust all roller alignment.
■ Wrinkles in sub-
strate.
1. Web guides not operating or properly
set.
2. Press out of alignment.
3. A roller or rollers out of alignment.
4. Build up of ink, tape or
foreign matter on press rollers.
5. Excessive web temperature
(film substrates).
6. Gauge inconstancies with substrate.
1. Check and clean web guides regular-
ly per manufacturer’s instructions.
Set web guides and position cores so
that web will unwind and rewind at
an equal measurement from the end
of the respective shafts.
2. Realign press.
3. Realign roller or rollers.
4. Clean all rollers of foreign matter.
5. Reduce web temperature.
6. Replace with new substrate.
■ Web failing to track
or follow a true
course through the
press.
DEFECT/INDICATOR PROBABLE CAUSE CORRECTIVE ACTION
PRESSROOM TROUBLESHOOTING CHART
(CONT‘D)
A
air chucks, 60-61
air shafts, 58-61
anilox rolls, 21, 93, 100, 102, 109-110, 114,
118-119, 123-124, 126, 127, 132, 135, 149,
224, 225, 226, 230
narrow-web press, 177, 178, 181, 184
wide-web press, 194-197, 203, 204, 205
corrugated press, 221
anvil rolls, 25
B
bare cylinder, 137
bearings
needle, 143
plain-sleeve, 141-142
rolling, 142-143, 148
C
CI press drives, 139-140
digital-servo, 140
direct, 139
line-shaft, 140
quadrant, 140
central-impression press, 7-10
chill drums, 96-97
cleanup procedures
corrugated press, 217-221
narrow-web press, 198-200
wide-web press, 203-206
cooling rolls, 82
corrugated-postprint press, 98-99, 207-221
checking color, 214
cleanup procedures, 217-221
doctor blade, 212-213, 219-220
feed device, 209
feed gates, 219
feed mechanism, 207
fountain roll, 212, 213, 219
impression (setting), 213, 214
inks, 98-99
ink distribution, 211
inking, 211, 212
plate mounting, 210, 211, 218
print stations, 206, 210, 211-212, 215, 217,
219
pull rolls, 207, 211
quality checks, 216
setting up, 207-214
sheet transport, 112, 117, 118-119
vacuum and belts, 111, 114, 116
vacuum and rollers, 110
pull rollers, 110
supply assurance, 207
counter-impression roll, 109-110
creaser/die cutter, 116
D
die cutting, 24-33, 189
cutting modes, 28
die-cutting stations, 24
platen die cutting, 102, 103, 108, 112, 115,
121
problem areas, 30-31
rotary die cutting, 26, 28-30, 102, 106,
112, 117, 121, 127
safety, 176
shapes, 28
substrate, 26
tools, 28-30
doctor blades, 170, 181, 183-184, 185, 186
down-folder, 100, 106
dryers, 80-82
air flow, 80
air temperature, 81
air velocity, 81
air volume, 81
interstation dryers, 80-81
main tunnel dryer, 80-81
maintenance, 150
time, 81
dual-gear systems, 139
E
EB varnishing, 95
emergency equipment, 171
emergency stops, 171
VOLUME 6 233
Index
234 FLEXOGRAPHY: PRINCIPLES & PRACTICES
F
film treating, 202
corona discharge, 90
stations, 90
flexo folder-gluer, 102, 110, 112-113, 116-117,
118, 120, 121, 134-139
flexo rolls
balancing, 128, 129
deflection, 131
forces on bearings, 129-130
modulus of elasticity, 131-132
total indicated runout (TIR), 131
folding-carton press, 10
freestanding off-line press, 124
G
gear backlash, 135, 140
gear-driven press, 109, 119-120, 122
gear drives, 132
bevel, 134, 148
central impression, 139-140
digital-servo, 140-141
helical, 133, 148
line-shaft, 140
spur, 132
worm, 134
gear mounting, 138-141
gear pitch, 134, 136, 137, 139-140
circumferential, 137, 139, 157, 159
diametral, 137, 138-139, 153-156
module, 137, 139, 158-163
gear train
pitch diameter, 136-138, 139-140
repeat length, 136-137, 139
H
hazardous material
labels, 144
disposal of, 175, 191, 206
I
ink
adding, 183, 187-188, 200-201, 215-216
adhesion tests, 189, 200, 202
distribution unit, 183, 196, 209-210
drying, 100, 124-125, 126, 177, 184, 187,
197, 200, 213, 214-215, 221, 223, 224, 225,
229, 230, 231
ink station, 105, 122, 173, 175, 178, 215,
220
transfer, 108, 111, 137, 149, 195
metering, 25, 110, 112-113, 114, 184, 194,
212-213
fountains, 14, 124, 136, 148, 184, 188
drying, 23, 60, 80-82, 91, 92, 100, 122-123,
126, 175, 182, 225
cleanup, 147, 148, 151, 169, 171, 176, 178,
190, 191, 203-206, 218-220
UV curing, 23, 95-96, 190, 224, 225
pH, 185-187, 198, 214-215
viscosity, 185-187, 198, 200, 201, 213, 214-
215, 225, 226, 228, 230, 231
in-line press, 10
J
job jacket (job history sheet), 178, 194
L
laminating, 92-95
solid adhesive laminating, 94
line shaft-driven press, 120-121
lockout switch, 171
N
narrow-web presses, 12-33, 177-192
advantages, 4
air shafts, 59
anilox rolls, 177, 178, 181, 184
cleanup procedures, 198-200
delivery system, 32
die-cutting stations, 24
cutting modes, 28
shapes, 28
tooling, 28-29
waste removal, 31
die installation, 179
drying and curing
UV curing, 23
laminating/varnishing, 23
dry registration, 181
edge guides, 181
fountain roll, 183
impression (setting), 184
in-feed tension control, 20-21, 48
ink distribution, 183
inking, 184-185, 187-188
plate cylinders, 13, 21-23
plate mounting/inspection, 181
print stations, 21, 177, 181, 183, 190
automatic register systems, 22
registration adjustment, 21
repeat length, 21
products printed, 18-19
quality checks, 188
register systems, 22
registration (setting), 184
rewind tension, 52
setup process, 177-189
setup stock, 181
types of
central impression press, 15-20, 80, 122
plate cylinder, 8
bearings, 141, 142
press drives, 139-140
in-line press, 16
web width, 16
register tolerance, 16
stack press, 17-18
platform press, 18
web width, 3, 12, 16
unwind, 14-20, 27, 92
unwind tension, 20, 47, 49
O
offset pivot guides, 67, 70
P
permanent-mesh coupling, 108-109, 118
plate cylinders
narrow-web press, 13, 21-23
wide-web press, 8, 10-12
demountable, 11
plate mounting, 107, 127, 136, 138, 181, 228
platen die cutting, 102, 103, 108, 112, 115,
plate-squeeze allowance, 121, 137-138
powder spray systems, 91-92
postprinting, 98, 99-100, 108, 122, 123, 125,
127
preprinting, 98, 99, 122
press approval form, 186, 199
press maintenance, 147-154
breakdown, 144
equipment care
brakes and clutches, 148
hydraulic cylinders and lines, 149
anilox rolls, 148, 149
fountain rolls, 149
electrical systems, 149
dryer, 150
auxiliary equipment, 150
lubrication, 146
preventative maintenance, 145
pressroom safety, 175-176
emergency stops, 171
lockout switch, 171
proper attire, 169
proper lifting, 169
safety signage, 170
tag-out, 173
print card, 113
printer/die cutter, 102, 112
printer-slotter, 112
printing diameter, 136-137, 138, 139
printing plates, 100, 101, 102, 108, 114, 117,
118, 120, 122
thickness of, 123
pull bands, 107-108, 110-111
pull-rolls, 109, 110-111, 114, 116, 118
R
registration, 102, 107, 110, 118-119, 120, 134,
139, 177, 181, 185, 188, 193, 198, 210
rewind equipment, 50, 57, 62, 71, 90, 94
constant tension, 53, 55
power requirements, 54
surface winders
center winder, 52
double-drum, 51
single-drum, 51-52
taper tension, 53, 55
rewind guiding, 71-72
rotary die, 13, 14, 23, 24-25, 28, 29, 30-32
rotary die cutting, 26, 28-30, 102, 106, 112,
117, 121, 127
S
safety signage, 170
servo-drive press, 121-122, 124
sheet cleaners, 125-126
brushes, 125
sheet feeders
kicker feeder, 103
lead-edge feeder, 104
belt type, 105
reciprocating belt type, 105
roller-type feed wheels, 105
cam roller feeder, 105
slotter/creaser, 114
slugs, 107
stack press, 5-6
static electricity, 80, 85-87, 173, 226, 228
causes, 83-84
controlling static, 86-87
grounding, 86-88
static eliminators, 87, 125
static neutralization, 87
steering guides, 67
entry spans, 69, 70
VOLUME 6 235
236 FLEXOGRAPHY: PRINCIPLES & PRACTICES
substrate, 48, 54, 98, 99, 102, 109, 110, 123,
125, 126, 177, 179, 181, 189, 203, 213, 216,
221, 222, 226, 229, 230, 231, 232
cleaning, 85, 89, 97
ionic, 89
corona field, 89-90
wind, 193-194
dryers
warm air, 124
infrared, 124
T
tag-out, 173
tension control, 43-48, 94
bowed roll, 49
cooling drum, 49-50
dancer, 40-41, 48-50, 55
in-feed, 47, 49
rewind tension, 52, 53, 71
automatic system, 39, 47, 50
dancer-roll system, 40-41
“draw” control system, 39
manual system, 38-39, 47
semiautomatic system, 45-46
tension transducer system, 41-43
splicing, 45-47
taper tension (see also rewind
equipment), 38
taper torque, 38
torque, 36-37, 38-40, 42-43, 52, 54-57,
58-60
unwind tension, 47-49
tension drives, 35-37
brakes/clutches, 36-37
motors, 35-36
tension transducer, 41-43
tension zones
intermediate, 35-37, 39, 42
rewind, 35, 50
unwind, 34-36, 49
U
UV curing, 23, 95-96, 190, 224, 225
UV varnishing, 95, 126
unwind equipment, 94
flying splice, 45-46
in-feed unit, 49
out-feed unit, 49
single-position, 44
tension-control system, 47, 50
up-folder, 100, 106
V
vacuum, 103, 104, 105, 111, 112, 117, 119,
121, 125, 126
W
web guiding systems
automatic, 64
hydraulic, 64
mechanical, 64
web position control, 65
edge guiding, 71
fixed sensor center, 62, 65
line (pattern) guiding, 65
moving sensor center, 65, 71
offset pivot guides, 67, 70
steering guides, 67-69
entry spans, 67
unwind guiding, 64, 65-66
web tension, 34, 38, 40-43, 47-49, 54, 56
web viewers
bent-web viewing, 75
oscillating mirror, 73
rotating drum mirror, 74
stroboscope, 73
video scanning, 75
optical encoder, 78
print mark sensor, 78
proximity sensor, 78
system configuration, 76-77
web width, 3, 62, 65, 66, 67, 68, 69-70, 74, 75,
90
narrow-web, 3, 12, 16
wide-web, 3, 10
wide-web presses, 3, 5-12, 193-206
anilox rolls, 194-195, 196-198
checking colors, 197-198
cleanup procedures, 203-206
doctor blade, 181, 183-184, 185, 186, 190,
196-197, 198, 202, 204, 205
fountain roll, 196-197, 204
impression (setting), 197
inking, 197, 200-201
plate cylinders, 8, 11-12
circumferential register control, 11
demountable, 11
side register control, 11
print stations, 193, 195, 196, 197, 203, 204
quality checks, 201
registration (setting), 197
setup process, 193-202
substrate wind, 193
types of
central-impression press, 7-10
central-impression drum, 9, 49
folding carton press, 10
in-line press, 10
stack press, 5-6
web width, 3, 10