Phenomenon: during printing, the ink in the printing plate dot is dry, resulting in incomplete dot.
reason:
A. Solvent and printing speed do not match, drying too fast.
B. The position of the scraper is too far from the impression point, and the ink in the concave eye is exposed to the air for a long time.
C. The diameter of gravure roller is too large, and the immersion in the ink tray is too shallow.
D. The hot air in the drying box leaks out and blows to the surface of the roller.
E. When the machine stops for a long time, the roller idles, the ink in the mesh can not be transferred, and gradually dry.
F. Impurities mixed into the ink caused. When the substrate is running, it often generates static electricity, adsorbs the dust and impurities in the environment into the ink and enters the mesh to cause blocking
G. Caused by poor quality of copper plate. In the process of making the plate roller, the inner wall of mesh is rough, the chromium plating is uneven, and the burr is produced during grinding, which affects the ink transfer rate and causes blocking in serious cases
H. Poor ink state, ink deterioration, misuse of solvents, mixing of different inks seriously affect the solubility of ink, resulting in blocking
1. Chemical changes. For the two-liquid reactive ink, with the printing process, cross-linking and other chemical reactions occur gradually. Make the fluidity of ink worse, viscosity increase, transfer rate will be reduced, resulting in blocking.
resolvent:
a. Use a solvent that is compatible with printing speed, especially when the temperature is high, use slow drying solvent appropriately.
b. The distance between the squeegee and the embossing point should be shortened as far as possible in the range where the printing quality is not affected
c. Maintain and check the leakage of dry hot air.
d. To often stir the ink in the ink tray, so that the ink in the flow state, timely add new ink, reduce the production of ink peel.
e. Before starting the machine, wipe the plate roller with solvent; in printing, try to avoid long-time shutdown. If it is necessary to stop for a long time, clean the plate roller first, or immerse the plate roller into the ink for hollow rotation, but it is not suitable for too long.
f. When the ink deterioration, misuse of solvents, mixed with different inks, to replace the ink, wash ink tank and circulation pump.
g. If the quality of copper plate mesh inner wall is poor, it should be re plate.