From the four aspects of ink, printing plate, doctor blade, solvent, etc., the reasons for the problem of printing knife line are comprehensively solved, and this problem is completely solved.
First, the ink factor
1, the effect of ink viscosity
The viscosity of the ink should match the printing speed. The viscosity of the ink is too high, and the adhesion to the plate cylinder is too strong. It is not conducive to scraping the excess ink of the plate by the squeegee, and the probability of printing the knives is high. The viscosity of the ink should be measured and controlled regularly during the printing process, usually measured every 20 minutes to 30 minutes.
2, the effect of ink drying
The ink dries too fast and is prone to crusting. If the crust is not dissolved during the ink circulation, it will stick to the edge or the bottom of the knife once it comes into contact with the squeegee, resulting in a printed knives. If the ink circulation system uses an open ink tank, ink crusts and agglomeration are more likely to occur. In order to reduce the occurrence of such cutter line failure, the ink in the ink tank should be stirred frequently; an appropriate amount of slow drying agent should be added as needed; if necessary, a sealing cover can be added to effectively control and reduce the printing cutter line failure.
3, the impact of ink fineness
The fineness of the pigment particles has a direct influence on the frequency of occurrence of the cut line. For example, the pigment particles used in the blue ink have high hardness, and it is difficult to achieve very fine particle size even after sufficient grinding, and it is easy to damage the scratching during the printing process. The knife or the effect of the ink scraping often causes a knife line failure when printing blue ink.
4, the impact of ink activity
In the ink production process, a certain amount of active agent is generally added. The plate cylinder also has a certain activity after chrome plating. If the activity of the ink and the plate cylinder is too high, the active material will adhere firmly to the roller during printing, and the squeegee is difficult to scrape it to form a knife. line. At this time, the plate cylinder is first cleaned to remove the active material on the surface, and an activity slowing agent is added to the ink to eliminate the cut line.
5, the impact of ink quality
When the ink is stored for too long, the solvent balance changes, causing the ink to dissolve, or the ink is mismatched and used improperly, causing a chemical reaction, which causes the ink to precipitate. During the printing process, the precipitate in the ink tends to accumulate at the doctor blade to cause the knife line, and the ink needs to be replaced.
Second, the printing factor
1. Influence of layout finish
If the gravure printing plate fails to polish the burr during polishing, during the printing process, the ink with burrs on the plate surface is not easy to be scraped, and in severe cases, the squeegee is damaged, thereby forming a knives. For printing knives caused by rough surface of the printing plate, the printing plate can be lightly polished with 1200 mesh fine sandpaper, but it is generally best not to polish the printing plate to avoid damage to the printing plate.
2, the impact of the hardness of the chromium layer
When making plates, if the chrome plating is too long, the hardness of the chrome layer on the surface of the plate is too high, and it is easy to damage the squeegee. Conversely, if the chrome plating is too short, the chrome layer on the surface of the plate is too soft, and the squeegee is likely to damage the plate, and a fixed cut line appears on the print.
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