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.
