Dust
This is a phenomenon in which filler (microscopic inorganic material) on the surface of YUPO adheres to and builds up on the blankets during printing such that the blankets become white and sucker marks or roller marks appear on the printed materials, producing an overall roughness.
The guideline for the number of continuous prints that can be made under good printing conditions varies depending on the grade. The pattern also has an effect.
- Grades with relatively more dust
→ TPRA, BLR, SGS (adhesive product), QJJ, and WCFA, etc. (Estimated number of continuous prints: 500 to 2,000 sheets) - Grades with relatively little dust
→ FGS, GAR, FRR (G) (Estimated number of continuous prints: 2,000 to 5,000 sheets) - Grades with very little dust
→ FRB (G), FEB (G), FEBA (Estimated number of continuous prints: 10,000 sheets)
If the printing conditions are not appropriate and ink emulsification is strong, the effect of dust will appear more quickly.
In extreme cases, dust problems (sucker marks and roller marks) may occur after several hundred sheets even with FGS.
Preventive measures
- When the ink has emulsified, wash away the ink from the rollers, plates, and blankets and put in fresh inks. (Be sure that the viscosity of the ink does not drop.)
- Lower the suction pressure and contact pressure of the suckers and rollers as much as possible. If possible, position the rollers outside the pattern.
- Apply tape to the rubber portions of the suckers or cover them with a cloth having good ventilation properties such as gauze.
- Apply tape or PP tape to the rollers.
- If there are spare printing color units, carry out dust removal on the cylinder of the first color unit using water and ventilation.
In this case, the blanket on the dust removal cylinder should be washed every 500 to 1,000 sheets.