FILLING IN

This is an accumulation of ink on the plate surface and shoulders of the printing images especially with small type and halftone screened areas.

Cause
Too much ink transferred.
Debris or particles of pigments.
Incorrect design of letters, graphics, screen.
Ink with an incorrect solvent balance.
Incorrect setting of the rollers.
Wrongly prepared printing plate.
Ink transfer from the previous printing unit.
Excessive ink transfer.
pH or viscosity value out of control.

Solution
Use an anilox roller with a lower volume.
Use dispersed ink with small particles, check that the pump, hoses and ducts are clean.
Check that the design is suitable for printing by flexo.
Use the recommended mixtures of solvents.
Increase the pressure of the inking roller or the doctor blade or the closure of the doctor blade chamber.
Check the plate relief and the printing surface – check that the edges of the printing images are not round. If the printing plate is too soft use a plate with a higher shore hardness.
Check the drying speed of the solvents in the different colours and ensure that they are balanced between the Different printing decks.
Maintain the correct viscosity value – check that the anilox roller has the correct cell count l/cm (lpi) and volume.
Maintain the viscosity and pH level at a constant level – check that the ink containers are always covered with their lids.


Helmut Mathes, troubleshooting defects supplied curtesey of Flexo & Gravure Int''l 2011