Trouble Shooting Support for Flexographic and Rotogravure Inks

Mottled print – The printed has mottled or flecked appearance, with colored or black circles usually appearing in the light colors.

• SOLUTION:

1. (CAUSE: Viscosity too low) – Add non-diluted ink and adjust the viscosity, change the plate.
2. (CAUSE: Surface of plate in poor condition) – Add Thickener.
3. (CAUSE: Pollution “anti-foam, silicon, etc.”) – Carefully clean the plates, do not use materials likely to leave lint on.
4. (CAUSE: Fount roller or anilox in poor condition) – Check the condition of the roller, the wear on the anilox cylinder and check that the link cells are not blocked.
5. (CAUSE: Unequal absorption of the ink into the substrate) – Use softer plates or opaque inks.

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

• SOLUTION:

1. (CAUSE: Solvent based ink “the thinning solvent evaporates too quickly”) – Use a solvent with a lower evaporation rate.
2. (CAUSE: Water based ink “in correct pH”) – Add 2% to 3% of retarding solvent, add re-generator (1% to 2% every 3/4 hours.

Drying too slow – Lifting of the ink or marking of the feed rods, blocking in the spool, ink sticky.

• SOLUTION:

1. (CAUSE: Solvent based inks “Viscosity of the ink too high” the thinning solvent evaporates too slowly) – Reduce the viscosity with the recommended solvent.
2. (CAUSE: Water based inks “Viscosity too high”) – Dilute with water or viscosity reducer (2% to 5%) incorporate re-generator (1% to 2%).
3. (CAUSE: Problem with drying tunnel) – Check the temperature and the extraction system.

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

• SOLUTION:

1. (CAUSE: Ink not adapted to the substrate) – Use a suitable ink or consult the supplier.
2. (CAUSE: Substrate incorrectly treated or treatment has passed its expiry date) – 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.
3. (CAUSE: Insufficient drying) – Increase the drying temperature and if possible the air flow.

Print not intense enough:

• SOLUTION:

1. (CAUSE: Viscosity too low) – Add non-diluted ink or a concentrate.
2. (CAUSE: Anilox screen too fine) – Use an anilox with a coarser screen size.
3. (CAUSE: Anilox screen worn or blocked up) – Change or clean the anilox.

Print too intense:

• SOLUTION:

1. (CAUSE: Viscosity too high) – Reduce the viscosity with an appropriate thinner.
2. (CAUSE: Anilox screen too coarse) – Anilox screen too coarse.
3. (CAUSE: Doctor blade incorrectly adjusted) – Adjust the doctor blade so that it correctly wipes the cylinder.
4. (CAUSE: Color strength too high) – Adjust the doctor blade so that it correctly wipes the cylinder.

Poor ink transfer: The plate does not deposit enough ink unto the substrate.

• SOLUTION:

1. (CAUSE: Viscosity too low “drying on the plate”) – Add non-diluted ink, adjust the drying of the ink.
2. (CAUSE: Surface tension of the substrate too low or surface tension of the plate too high) – Check the treatment of the substrate and the surface energy of the plate.
3. (CAUSE: Pressure between the plate and the anilox incorrectly adjusted) – Adjust the pressure settings.
4. (CAUSE: Anilox screen worn or blocked up) – Change or clean the anilox.
5. (CAUSE: Anilox screen too fine) – Use a coarse screen.

Viscosity increases in the ink duct:

• SOLUTION:

1. (CAUSE: Solvent based inks “unsuitable solvent or imbalance due to evaporation”) – Add a more suitable solvent.
2. (CAUSE: Water based inks “Reduced pH”) – Add re-generator (1% to 2%)

Ink not homogeneous: Particles in suspension.

• SOLUTION:

1. (CAUSE: Wrong additive incorporated, causing precipitation) – Filter the ink in the ink duct, check that the product used is compatible with the ink. And the additives slowly, while agitating.

Moire effect: Blurred four colors print.

• SOLUTION:

1. (CAUSE: Incorrect ratio between the screen ruling of the plate and that of the anilox) – Use an anilox roller adapted to the print run.
2. (CAUSE: Plate screens not at right angle) – The color separation films should be corrected.

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

• SOLUTION:

1. (CAUSE: Ink not drying correctly) – Reduce the viscosity of the ink, change the thinning solvent to accelerate drying, change the balance of the thinners, increase the drying capacity and/or the volume of air.
2. (CAUSE: Substrate temperature too high before spooling) – Install a cooling system before the re-spooling.
3. (CAUSE: Spooling pressure too tight) – Reduce the spooling tension.

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

• SOLUTION:

1. (CAUSE: Pressure between plate and anilox too high) – Adjust the pressure correctly.
2. (CAUSE: Inks dries to rapidly) – Adjust the drying of the ink.
3. (CAUSE: Ink viscosity too high) – Dilute the ink.

Streaking: Wide streaks across the print.

• SOLUTION:

1. (CAUSE: Worn gears) – Replace the worn gears.
2. (CAUSE: Excessive tightening of the inking cylinder) – Check the thickness of the plate “using a too thin plate compensated by excess tightening”).