Excessive ink transfer to substrate. Excess colour strength.
Causes:
- Ink viscosity too high or too low with dot gain;
- Colour concentration too high;
- Ink film too thick;
- Contamination from previous colours;
- Nip pressure between rubber roll and anilox roll;
-Wrong anilox roll.
Solutions:
- Check and maintain correct ink viscosity, use a kiss impression only;
- Add extender to ink, reduce ink film thickness;
- Reduce ink thickness by lowering ink viscosity, increasing ink metering effectiveness, decreasing machine speed or anilox volume.Check doctor blade is parallel with a minimum pressure setting;
- Thoroughly clean press station between colour changes and replace ink;
- Set nip pressure to minimum setting or select fountain roll with a higher durometer;
- Change anilox roll specification to a lower cell volume.
