Incidents
- Mottled print
The print has a mottled or flecked appearance, with coloured or black circles usually appearing in light colours.
- Drying too rapid
The ink dries on the inking system (plate and cylinder) and hampers ink transfer.
- Drying too slow
Lifting of the ink, or marking of the feed rods. Blocking in the spool. Ink sticky.
- Poor adhesion of the ink to the substrate
Poor mechanical resistance (poor rub, adhesive tape, scratch resistance, etc.).
- Print not intense enough
- Print too intense
- Poor ink transfer
The plate does not deposit enough ink onto the substrate.
- Viscosity increases in the ink duct
- Ink not homogeneous
Particles in suspension.
- Moiré effect
Blurred four colour prints.
- Blocking in the reel
Spools stick together, making the prints unusable.
Print leaves marks on the underside of the substrate.
- Prints clogged up or slurred
Excess ink around halftone dots and small text and poor character definition
- Streaking
Wide streaks across the print.
Probable causes and remedies
1. Mottled print
The print has a mottled or flecked appearance, with coloured or black circles usually appearing in light colours. (back to incidents)
The print has a mottled or flecked appearance, with coloured or black circles usually appearing in light colours. (back to incidents)
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Cause
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Viscosity too low.
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Remedie
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Add non-diluted ink and adjust the viscosity.
Change the plate. |
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Cause
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Surface of plate in poor condition.
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Remedie
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Add thickener.
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Cause
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Pollution (anti-foam, silicone, etc.) of the plate.
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Remedie
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Carefully clean the plates. Do not use materials likely to leave lint on the plate.
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Cause
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Fount roller or anilox in poor condition.
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Remedie
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Check the condition of the roller, the wear on the anilox cylinder and check that the ink cells are not blocked.
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Cause
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Unequal absorption of the ink into the substrate.
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Remedie
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Use softer plates or opaque inks.
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2. Drying too rapid
The ink dries on the inking system (plate and cylinder) and hampers ink transfer.
(back to incidents)
The ink dries on the inking system (plate and cylinder) and hampers ink transfer.
(back to incidents)
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Cause
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Solvent based inks:
The thinning solvent evaporates too quickly. |
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Remedie
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Use a solvent with a slower evaporation rate.
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Cause
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Water based inks: incorrect pH.
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Remedie
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Add 2-3 % of retarding solvent. Add regenerator (1 to 2 % every 3/4 hour).
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3. Drying too slow
Lifting of the ink, or marking of the feed rods. Blocking in the spool. Ink sticky.
(back to incidents)
Lifting of the ink, or marking of the feed rods. Blocking in the spool. Ink sticky.
(back to incidents)
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Cause
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Solvent based inks:
Viscosity of the ink too high. The thinning solvent evaporates too slowly. |
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Remedie
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Reduce the viscosity with the recommended solvent.
Use a solvent with a faster evaporation rate. |
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Cause
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Water based inks:
Viscosity too high. |
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Remedie
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Dilute with water or viscosity reducer (2 to 5 %).
Incorporate regenerator (1 to 2 %). |
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Cause
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Problem with drying tunnel.
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Remedie
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Check the temperature and the extraction system.
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4. Poor adhesion of the ink to the substrate
Poor mechanical resistance (poor rub, adhesive tape, scratch resistance, etc.)
(back to incidents)
Poor mechanical resistance (poor rub, adhesive tape, scratch resistance, etc.)
(back to incidents)
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Cause
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Ink not adapted to the substrate.
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Remedie
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Use a suitable ink or consult the supplier.
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Cause
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Substrate incorrectly treated or treatment has passed its expiry date.
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Remedie
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Check the surface tension of the substrate or consult the supplier to check the expiry date of the treatment.
Check the possibility of applying a pre-lacquer varnish or primer varnish or use CORONA treatment. |
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Cause
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Insufficient drying.
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Remedie
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Increase the drying temperature and, if possible, the air flow.
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Cause
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Viscosity too low.
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Remedie
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Add non-diluted ink or a concentrate.
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Cause
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Anilox screen too fine.
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Remedie
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Use an anilox with a coarser screen size.
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Cause
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Anilox screen worn or blocked up.
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Remedie
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Change or clean the anilox.
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Cause
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Viscosity too high.
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Remedie
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Reduce the viscosity with an appropriate thinner.
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Cause
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Anilox screen too coarse.
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Remedie
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Anilox screen too coarse.
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Cause
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Doctor blade incorrectly adjusted.
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Remedie
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Adjust the doctor blade so that it correctly wipes the cylinder.
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Cause
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Colour strength too high.
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Remedie
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Reduce the intensity with an appropriate decolorant.
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Cause
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Viscosity too low.
Drying on the plate. |
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Remedie
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Add non-diluted ink.
Adjust the drying of the ink. |
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Cause
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Surface tension of the substrate too low or surface tension of the plate too high.
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Remedie
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Check the treatment of the substrate and the surface energy of
the plate. |
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Cause
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Pressure between the plate and the anilox incorrectly adjusted.
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Remedie
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Adjust the pressure settings.
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Cause
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Anilox screen worn or blocked up.
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Remedie
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Change or clean the anilox.
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Cause
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Anilox screen too fine.
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Remedie
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Use a coarser screen.
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Cause
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Solvent based inks:
Unsuitable solvent or imbalance due to evaporation. |
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Remedie
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Add a more suitable solvent.
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Cause
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Water based inks:
Reduced pH. |
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Remedie
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Add regenerator (1 to 2 %).
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Cause
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Wrong additive incorporated, causing precipitation.
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Remedie
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Filter the ink in the ink duct.
Check that the product used is compatible with the ink. Add the additives slowly, while agitating. |
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Cause
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Incorrect ratio between the screen ruling of the plate and that of the anilox.
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Remedie
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Use an anilox roller adapted to the print run.
In Flexo printing, the ratio of the plate screen to that of the anilox must be 1 to 3.5 or even 4. |
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Cause
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Plate screens not at right angle.
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Remedie
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The colour separation films should be corrected.
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11. Blocking in the reel
Spools stick together, making the prints unusable.
Print leaves marks on the underside of the substrate. (back to incidents)
Spools stick together, making the prints unusable.
Print leaves marks on the underside of the substrate. (back to incidents)
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Cause
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Ink not drying correctly.
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Remedie
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Reduce the viscosity of the ink.
Change the thinning solvent to accelerate drying. Change the balance of thinners. Increase the drying capacity and/or the volume of air. |
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Cause
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Substrate temperature too high before spooling.
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Remedie
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Install a cooling system before the re-spooling.
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Cause
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Spooling pressure too tight.
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Remedie
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Reduce the spooling tension.
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12. Prints clogged up or slurred
Excess ink around halftone dots and small text and poor character definition.
(back to incidents)
Excess ink around halftone dots and small text and poor character definition.
(back to incidents)
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Cause
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Pressure between plate and anilox too high.
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Remedie
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Adjust the pressure correctly.
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Cause
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Ink dries too rapidly.
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Remedie
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Adjust the drying of the ink.
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Cause
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Ink viscosity too high.
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Remedie
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Dilute the ink.
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Cause
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Worn gears.
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Remedie
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Replace the worn gears.
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Cause
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Excessive tightening of the inking cylinder.
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Remedie
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Check the thickness of the plate (using a too thinplate compensated by excess tightening).
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