Excessive foam present in the printing unit, tray or ink pump unit.
Causes:
– Ink too weak or too low in viscosity;
– Plate surface uneven;
– A coating left on the plate surface from plate making;
– Dirty or pitted impression cylinder;
– Uneven or unreceptive substrate;
– Ink not wetting out on substrate;
– Ink reticulation caused by excessive of antifoam;
– Foreign matter collecting on plate surface;
– Worn anilox roll.
Solutions:
– Add fresh ink or medium to correct viscosity for greater opacity level;
– Increase plate to substrate impression. Increase ink viscosity. Increase ink film thickness. Use softer plate durometer;
– Wash plate thoroughly with a compatable cleaning solution. Remake plate;
– Impression roller must be thoroughly cleaned of ink and other foreign materials;
– Use softer or compressible plates or cushion mounting tape. Check treatment levels on substrate;
– Ensure solvent balance is correct. Change ink system. Contact ink and substrate supplier;
– Replace with fresh ink;
– Thoroughly wash plate. Check ink filters are working. Check supplier re detack level of plate. Ensure plate surface is not wiped with aggressive solvents;
– Examine anilox roll for wear, plugging or for excessive land areas. Use a higher screen anilox roll.
