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A detailed analysis is made in
this problem solving guide for common problems
faced in Gravure . A brief description
is given of each dilemma along with the possible
causes and remedies. If you still have more
questions , please use our Enquiry section to ask our experts.
Abrasion
?
| How
Recognised: Cylinder Wear. Doctor
blade wear. |
| CAUSE |
REMEDY |
| 1.Poor dispersion
|
1.Re-grind ink |
| 2.Specific pigment
|
2.Better pigment selection
|
| 3.Foreign matter |
3.Filter ink |
| 4.Soft chrome &/or
copper |
4.Remake cylinder
|
| 5.Excessive blade
pressure |
5.Reduce
blade pressure |
| 6.Corrosive ink |
6.Consult ink maker
|
Adhesion ?
| How
recognised: Ink or varnish does
not bind to each other
or to the substrate. |
| CAUSE |
REMEDY |
| 1.Improper thinner
used |
1.Consult ink maker
for proper thinner |
| 2.Ink film not cured
|
2.Increase oven temperature |
3.Improper
ink used
|
3.Consult ink maker
|
Blocking ?
| How
recognised: Ink adheres to back
of web in rewind. |
| CAUSE |
REMEDY |
| 1.Oven temperature
too low |
1.Check oven temperature
|
| 2.Thinner too slow
for press speed |
2.Use faster thinner
|
| 3.Trapped
solvent |
3.Use proper solvent
balance. Check for surface drying
|
| 4.Web too hot when
rewound |
4.Reduce web temperature,
use chill rolls |
| 5.Excessive
rewind pressure |
5.Adjust web tension
|
| 6.Ink too soft |
6.Consult ink maker
|
Blushing ?
| How
recognised: Printed ink has milky
white looks |
| CAUSE |
REMEDY |
| 1.Improperly balanced
thinner |
1.Use balanced thinner
|
| 2.Humidity too high |
2.Add slow prime solvent
to thinner |
| 3.Ink
contaminated with water etc.
|
3.Discard ink - consult
ink maker |
Cobwebs ?
| How
recognised: Spider web-like build
up on blade, impression roll cylinder
& in oven |
| CAUSE |
REMEDY |
| 1.Ink starvation |
1.Check pipes for
ink blockage |
| 2.Oven
imbalance |
2.Adjust air flow
for a slight negative pressure |
| 3.Oven air velocity
too high |
3.Reduce air flow
in oven |
| 4.Ink drying too fast
|
4.Slow reducer |
| 5.Ink
viscosity too high |
5.Reduce viscosity
|
Drying-in ?
| How
recognised: Weak print. Colour
intensity varies light to dark |
| CAUSE |
REMEDY |
| 1.Ink drying too fast
|
1.Scrub cylinder.
Retard ink with slower reducer |
| 2.Ink viscosity too
high |
2.Reduce viscosity |
| 3.Ink not flowing
out |
3.Add clear extender
|
| 4.Air blowing on cylinder
|
4.Balance oven to
achieve negative pressure |
| 5.Poor wipe |
5.Adjust doctor blade
|
| 6.Too much impression
pressure |
6.Adjust impression
pressure |
| 7.Ink
contaminated |
7.Replace with fresh
ink |
Foaming ?
| How
recognised: Air bubbles on surface
of ink |
| CAUSE |
REMEDY |
| 1.Air
entrapped in ink |
1.Increase
level of ink sump to prevent starvation
2.Slow pump and application flow
3.Use recommended defoamer |
Hazing Scumming or Toning ?
| How
recognised: Very light and uneven
transfer of ink in non-image area
|
| CAUSE |
REMEDY |
| 1.Blade pressure too
light-blade angle too flat |
1.Increase blade pressure&
sharpen blade angle |
| 2.Poor knife edge
on doctor blade |
2.Replace blade-use
pregroung lamella type blade |
| 3.Ink dried on bottom
of blade |
3.Clean blade thoroughly
or replace |
| 4.Ink in non-image
area not drying between blade and
impression |
4.Put air on cylinder-move
blade away from nip. Put air on
cylinder. |
| 5.Rough
cylinder |
5.Hand polish or rechrome
|
Misprints (Voids) ?
| How
recognised: Solid areas show random
areas in which ink is not transferring-
Dots missing in process printing
|
| CAUSE |
REMEDY |
| 1.Rough
substrate |
1.Increase impression
|
| 2.Partially
plugged cylinder |
2.Scrub etch with
solvent & brass brush |
| 3.Impression
too light |
3.Increase impression
pressure |
| 4.Ink
starvation |
4.Increase applicator
flow |
| 5.Damaged
or pitted impression roll |
5.Regrind or replace
impression roll
|
| 6.Particles
in ink |
6.Filter ink through
fine ink filter |
| 7.Excessive
foam |
7.See remedies for
foam |
Mottled print ?
| How
recognised: Solid areas have variation
in colour - grainy pattern |
| CAUSE |
REMEDY |
| 1.Viscosity
too low |
1.Increase viscosity
with fresh ink |
| 2.Pigment
selection |
2.Better pigment combination
for colour match |
| 3.Ink
solids too low-ink not flowing |
3.Add pigmented extender
|
| 4.Cylinder
too deep or cylinder worn out |
4.No immediate solution-replace
cylinder |
Offset on idler roller ?
| How
recognised: Printed image transferring
to idle roll |
| CAUSE |
REMEDY |
| 1.Ink
drying too slowly |
1.Use faster thinner
blend |
| 2.Ink
viscosity too high |
2.Reduce viscosity
|
| 3.Oven
temperature too low |
3.Increase oven temperature
and air velocity |
| 4.Web
temperature too high |
4.Decrease oven temperature
|
| 5.Ink
too soft |
5.Consult ink maker
for proper non-stick additives |
| 6.Improper
ink for substrate |
6.Consult ink maker
|
Poor trapping ?
| How
recognised: Over printing ink
not transferring over underlying
inks pick back. |
| CAUSE |
REMEDY |
| 1.First down ink not
drying |
1.Increase oven temperature
and air velocity |
| 2.Over printing ink
redisolving 1st down ink picking
back |
2.Consult ink maker
for lean reducer blend. Sandwich
dissimilar inks |
| 3.No
pick back but ink not transferring
to 1st down ink or not flowing |
3.Use slower reducer
mix reduce oven temperature of 1st
down ink |
Pin holes ?
| How
recognised: Small uncoloured holes
in printed area |
| CAUSE |
REMEDY |
| 1.Rough or contaminated
substrate |
1.Increase impression
pressure |
| 2.Ink fails to flow
out |
2.Reduce viscosity
- retard ink drying |
| 3.Wrong
ink for substrate |
3.Consult ink maker
for reformulation |
| 4.Contaminated ink
|
4.Discard ink |
Rub or scuff ?
| How
recognised: Dried ink rubs off
printed product |
| CAUSE |
REMEDY |
| 1.Ink improperly dried
|
1.Increase oven temp.,
air velocity |
| 2.Ink too soft |
2.Use additives as
recommended by ink maker |
| 3.Insufficient
wax or slip compound |
3.Consult ink maker
for wax additive |
Screening ?
| How
recognised: Definite pattern of
cell walls. Ink not flowing out |
| CAUSE |
REMEDY |
| 1.Ink
viscosity too high |
1.Reduce viscosity
with recommended reducer |
| 2.Ink drying in cells
|
2.Set oven for negative
pressure to prevent air from blowing
on cylinder |
| 3.Improper ink for
substrate |
3.Consult ink maker
for proper ink |
| 4.Ink contaminated
by foreign matter |
4.Thoroughly flush
system and start with fresh ink
|
| 5.Cylinder
worn or cell walls too wide |
5.Remake cylinder
|
| 6.Ink starvation |
6.Increase ink flow,
raise inner pan |
Snowflakes ?
| How
recognised: Small random spots
of unprinted area showing through
a deposited ink missing dots in
process |
| CAUSE |
REMEDY |
| 1.Ink drying too fast
|
1.Retard with slow
reducer |
| 2.Ink viscosity too
high |
2.Reduce viscosity
|
| 3.Rough stock |
3.Increase impression
|
| 4.Cylinder plugged
|
4.Scrub cylinder thoroughly
|
| 5.Cylinder
worn |
5.Replace cylinder
|
Static ?
| How
recognised: Hair lines of ink
starting from printed area occurring
in random directions |
| CAUSE |
REMEDY |
| 1.Ink viscosity too
low |
1.Raise viscosity
with fresh ink |
| 2.Static in web |
2.Use tinsel or static
bar |
| 3.Low
moisture contact |
3.Use steam generator
to add moisture |
Streaks(Hard) ?
| How
recognised: Distinct solid lines
that occur in non-image area.
This condition may be continious
or intermittent. Lines move as
blade oscillates |
| CAUSE |
REMEDY |
| 1.Abrasion or mars
in surface of cylinder |
1.Repolish cylinder
|
| 2.Worn or nicked doctor
blade |
2.Rehone or replace
Doctor blade |
| 3.Insoluble
particles |
3.Filter or replace
with fresh ink |
Streaks (Soft) ?
|
How
recognised: Relatively wide streaks
that show up in non- image area.
Usually in non - systematic pattern |
| CAUSE |
REMEDY |
| 1.Soft particles behind
doctor blade caused by contamination
of ink |
1.Clean blade well
filter or replace ink. Thoroughly
flush system |
| 2.Excessive ink |
2.See remedy for foam
|
| 3.Damaged doctor blade
|
3.Replace doctor blade
|
| 4.Worn cell walls
on trailing edge design |
4.Replace cylinder
|
Striation ?
| How
recognised: Wavy print pattern
in direction of web travel |
| CAUSE |
REMEDY |
| 1.Ink viscosity too
low |
1.Raise viscosity
|
| 2.Vehicle solid too
low |
2.Add high solids
extender |
| 3.Ink contaminated
|
3.Replace ink |
| 4.Too much impression
|
4.Reduce impression
pressure |
| 5.Worn
cylinder, incorrect engraving |
5.Replace cylinder
|
| 6.Ink not wetting
substrate |
6.Consult ink maker
|
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