The unscraped ink is left in the non-graphic part of the printed composite packaging bag , and transferred to the film to form an atomized, sheet-like ink stain, and black and blue inks are more likely to appear.
cause:
1. Scraper wear reduces ink scraping efficiency
2. The chrome plating quality of the printing plate is poor or the surface damage caused by abrasion
3. Impurities, coarse particles and other debris in the ink lifted the scraper
4. The adhesion of the ink to the printing plate is too strong or the ink scraper is not adaptable (poor lubrication adaptability)
Solution:
1. Increase scraper pressure, adjust scraper position and angle
2. Replace or grind the scraper
3. Caused by the rough surface of the printing plate, the printing plate should be polished
4. reduce the ink viscosity or concentration (, 5 - 10% thinners)
5. Reduce the speed or blow the air to the non-pattern position to make the unscraped ink dry quickly.
6. Replace the ink.
Albinism
The printing whitening phenomenon can be divided into solvent whitening and ink resin whitening.
1. Solvent whitening
Cause: This kind of whitening phenomenon mostly occurs in alcohol-soluble ink. When the humidity is high, due to the latent heat of evaporation of the solvent, the ink film will be cooled nearby, causing water to mix in and cause the ink to whiten. This phenomenon is more likely to occur when using solvents with high latent heat of evaporation.
Ethyl acetate: 87.63 cal / g toluene: 86.5 cal / g methanol: 363.3 cal / g
Isopropyl alcohol: 161.73 calories / gram Ethanol: 208.7 calories / gram Butyl ester: 79.3 calories / gram
Solution: Increase the environmental humidity as much as possible to reduce the ink drying speed.
2. Resin whitening
Cause: The balance of the solvent in the ink is poor, the true solvent evaporates first, and the diluent remains in the ink, causing the resin in the ink to precipitate and cause whitening.
Solution: The proportion of the solvent replacement formula; ink replacement; adding a real solvent with a slow evaporation rate.
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