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.
