Irregular edges around a print, often undesirable marks made on the image’s trailing edges, generally caused by an excessive build-up of ink.
Causes:
– Incorrect pressure set up in printing unit;
– Ink drying on plate;
– Improper setting of metering system;
– Uncontrolled ink viscosity;
– Incorrect solvent balance;
– Debris and dust being picked up from the substrate;
– Out of true plate cylinder;
– Static electricity.
Solutions:
– Reset pressure between all rollers;
– Clean plates thoroughly. Speed up press. Slow down drying by adding slower solvents. Ensure ink unit tray covers are in place;
– Reset pressure settings between fountain roll nip and doctor blade assembly;
– Maintain correct viscosity, do not allow to drift too high. Use ink tray covers to improve ink solubility;
– Modify solvent balance;
– Clean off when necessary, lower ink viscosity to lower its tack. Use web cleaning devices when required. Tacky polymers not cured properly during manufacture;
– Check roller is true;
– Use static eliminators. Reduce tack of the ink and clean plate.
