Flexographic Plates Troubleshooting: Problems, Solutions and Causes – Part 3

This is a continuation to the series of flexo plates troubleshooting part 1 and 2.

If you have not read the first article on flexo plates troubleshooting, we link it here :
Flexographic Plates Troubleshooting : Problems, causes and solution – Part 1
Flexographic Plates Troubleshooting : Problems, causes and solution – Part 2

Blocking:

•    Problem: Ink transfer from one print to the next.

•    Causes: Ink drying problems; web tension issues; substrate humidity problem.

•    Solutions:  Optimization of ink, substrate and dryer parameters.

Ink splashing:

• Problem:: Ink splashing.

• Causes: Ink viscosity too low; wrong anilox specification (volume too high and/or line count too low).

• Solutions: Correct ink viscosity; optimize anilox specification.

Registration issues :

• Problem:: Registration problems in print.

• Causes: Issues during plate mounting; equipment problems during plate making (drying unit); plate orientation on imaging system; separations made from different raw material batches.

• Solutions: Confirm functionality of plate making equipment; image separations in the same orientation on the CDI; use plates for different separations from same raw material box/batch.

Element edges start to print earlier:

• Problem:: Element edges start to print early.

• Causes: Cupping issue; high anilox to plate or plate to substrate impression.

• Solutions: Optimization of plate making parameters (especially dry times); optimization of impression settings on press

“Unsharp“ printing

• Problem:: Unsharp printing result; high dot gain.

• Causes: Excessive plate swelling from unsuitable solvents or cleaners could result in plate softening during printing; high impression settings; possibly „cupping“ issue; possibly ink issue.

• Solutions: Confirmation of suitable solvents; possibly reduce impression settings.

Ink transfer issues

• Problem:: Ink transfer issues.

• Causes: General ink issue; ink drying on the anilox roller; plate surface contaminated.

• Solutions: Confirm the condition of the ink; cleaning of plate surface and anilox roller.

“Filling in“ of fine elements

• Problem:: Fine printed elements start to fill in with ink .

• Causes: High anilox to plate impression; wrong ink viscosity.

• Solutions: Confirm anilox settings; check and correct ink viscosity. 

Ink “bleeding“

• Problem : Ink starts to bleed; no defined screen structures visible.

• Causes: Improper pigment use in ink formulation; pH issue in water based ink formulation.

• Solutions: Consult your ink manufacturer.

“Dirty printing“ in transitions of flexo plates

• Problem:: Screen transitions start to print dirty.

• Causes: High anilox to plate impression setting; low ink viscosity; high anilox volume; shallow intermediate depths or plate relief.

• Solutions: Optimization of press and ink parameters. Correction of plate making issues.

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