TECHNICAL INFO




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Troubleshooting
Incidents
 
  1. Mottled print
    The print has a mottled or flecked appearance, with coloured or black circles usually appearing in light colours.

     

  2. Drying too rapid
    The ink dries on the inking system (plate and cylinder) and hampers ink transfer.

  3. Drying too slow
    Lifting of the ink, or marking of the feed rods. Blocking in the spool. Ink sticky.

     
  4. Poor adhesion of the ink to the substrate
    Poor mechanical resistance (poor rub, adhesive tape, scratch resistance, etc.).

     
  5. Print not intense enough

  6. Print too intense
     
  7. Poor ink transfer
    The plate does not deposit enough ink onto the substrate.

     
  8. Viscosity increases in the ink duct
     
  9. Ink not homogeneous
    Particles in suspension.

     
  10. Moiré effect
    Blurred four colour prints.

  11. Blocking in the reel
    Spools stick together, making the prints unusable.
    Print leaves marks on the underside of the substrate.

     
  12. Prints clogged up or slurred
    Excess ink around halftone dots and small text and poor character definition

     
  13. 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)

Cause
Viscosity too low.
Remedie
Add non-diluted ink and adjust the viscosity.
Change the plate.
Cause
Surface of plate in poor condition.
Remedie
Add thickener.
Cause
Pollution (anti-foam, silicone, etc.) of the plate.
Remedie
Carefully clean the plates. Do not use materials likely to leave lint on the plate.
Cause
Fount roller or anilox in poor condition.
Remedie
Check the condition of the roller, the wear on the anilox cylinder and check that the ink cells are not blocked.
 
Cause
Unequal absorption of the ink into the substrate.
Remedie
Use softer plates or opaque inks.
 
 
2. Drying too rapid
The ink dries on the inking system (plate and cylinder) and hampers ink transfer.
(back to incidents)


Cause
Solvent based inks:
The thinning solvent evaporates too quickly.
Remedie
Use a solvent with a slower evaporation rate.
Cause
Water based inks: incorrect pH.
Remedie
Add 2-3 % of retarding solvent. Add regenerator (1 to 2 % every 3/4 hour).
 
3. Drying too slow
Lifting of the ink, or marking of the feed rods. Blocking in the spool. Ink sticky.
(back to incidents)

Cause
Solvent based inks:
Viscosity of the ink too high.
The thinning solvent evaporates too slowly.
Remedie
Reduce the viscosity with the recommended solvent.
Use a solvent with a faster evaporation rate.
Cause
Water based inks:
Viscosity too high.
Remedie
Dilute with water or viscosity reducer (2 to 5 %).
Incorporate regenerator (1 to 2 %).
Cause
Problem with drying tunnel.
Remedie
Check the temperature and the extraction system.
 
4. Poor adhesion of the ink to the substrate
Poor mechanical resistance (poor rub, adhesive tape, scratch resistance, etc.)
(back to incidents)

Cause
Ink not adapted to the substrate.
Remedie
Use a suitable ink or consult the supplier.
Cause
Substrate incorrectly treated or treatment has passed its expiry date.
Remedie
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.
Cause
Insufficient drying.
Remedie
Increase the drying temperature and, if possible, the air flow.




 
5. Print not intense enough (back to incidents)
 
Cause
Viscosity too low.
Remedie
Add non-diluted ink or a concentrate.
Cause
Anilox screen too fine.
Remedie
Use an anilox with a coarser screen size.
Cause
Anilox screen worn or blocked up.
Remedie
Change or clean the anilox.
 
6. Print too intense (back to incidents)
 
Cause
Viscosity too high.
Remedie
Reduce the viscosity with an appropriate thinner.
Cause
Anilox screen too coarse.
Remedie
Anilox screen too coarse.
Cause
Doctor blade incorrectly adjusted.
Remedie
Adjust the doctor blade so that it correctly wipes the cylinder.
Cause
Colour strength too high.
Remedie
Reduce the intensity with an appropriate decolorant.
 
7. Poor ink transfer
The plate does not deposit enough ink onto the substrate. (back to incidents)

Cause
Viscosity too low.
Drying on the plate.
Remedie
Add non-diluted ink.
Adjust the drying of the ink.
Cause
Surface tension of the substrate too low or surface tension of the plate too high.
Remedie
Check the treatment of the substrate and the surface energy of
the plate.
Cause
Pressure between the plate and the anilox incorrectly adjusted.
Remedie
Adjust the pressure settings.
Cause
Anilox screen worn or blocked up.
Remedie
Change or clean the anilox.
Cause
Anilox screen too fine.
Remedie
Use a coarser screen.
 
8. Viscosity increases in the ink duct (back to incidents)
 
Cause
Solvent based inks:
Unsuitable solvent or imbalance due to evaporation.
Remedie
Add a more suitable solvent.
Cause
Water based inks:
Reduced pH.
Remedie
Add regenerator (1 to 2 %).
 
9. Ink not homogeneous
Particles in suspension. (back to incidents)
 
Cause
Wrong additive incorporated, causing precipitation.
Remedie
Filter the ink in the ink duct.
Check that the product used is compatible with the ink.
Add the additives slowly, while agitating.
 
10. Moiré effect
Blurred four colour prints. (back to incidents)
 
Cause
Incorrect ratio between the screen ruling of the plate and that of the anilox.
Remedie
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.
Cause
Plate screens not at right angle.
Remedie
The colour separation films should be corrected.
 
11. Blocking in the reel
Spools stick together, making the prints unusable.
Print leaves marks on the underside of the substrate.
(back to incidents)

Cause
Ink not drying correctly.
Remedie
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.
Cause
Substrate temperature too high before spooling.
Remedie
Install a cooling system before the re-spooling.
Cause
Spooling pressure too tight.
Remedie
Reduce the spooling tension.
 
12. Prints clogged up or slurred
Excess ink around halftone dots and small text and poor character definition.
(back to incidents)



Cause
Pressure between plate and anilox too high.
Remedie
Adjust the pressure correctly.
Cause
Ink dries too rapidly.
Remedie
Adjust the drying of the ink.
Cause
Ink viscosity too high.
Remedie
Dilute the ink.
 
13. Streaking
Wide streaks across the print. (back to incidents)
 
Cause
Worn gears.
Remedie
Replace the worn gears.
Cause
Excessive tightening of the inking cylinder.
Remedie
Check the thickness of the plate (using a too thinplate compensated by excess tightening).
 
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