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.
