The Causes and Countermeasures of Plastic Gravure Cutter Line (I)

There are many quality problems with gravure printing on plastic films, and cutting lines are one of the most common failures. The production of knife lines causes the products to be scrapped, which can easily cause economic losses. As a printing company engaged in flexible packaging, it is necessary to analyze and summarize the causes, and find the corresponding solutions, and ultimately make the knife line failure to the lowest point.
The relationship between the production of the knife line and the viscosity of the ink The production of the knife line has a direct relationship with the viscosity of the ink. In actual production, the higher the viscosity of the ink, the easier it is to produce a knife line during printing. This type of knife line generally exhibits two forms on the printed product. The first type of knife line is a fine, streamlined shape, which generally does not drag too long. Instead, it appears intermittently on the printed product. The starting point of the micro flow-shaped knife line is mostly close to the printing pattern, and the knife line is used. The starting point is generally coarser than the end, and if it is not observed in actual production, this fine streamlined knife line can be easily ignored. This streamlined knife line is often the root cause of quality accidents and must be taken seriously. There are several ways to solve this streamlined knife line, which is also commonly used by printing staff, but it must be determined according to the actual situation.
a. A 5cm wide, 15cm long, 140um thick soft blade is ground very smoothly, lightly picking at the knife line, under normal circumstances, this tiny streamlined knife line will be improved. This kind of operation is generally completed in the operation of the machine, which requires that you must be familiar with the operator to complete, so as to avoid easy to make mistakes, resulting in unnecessary losses.
b. The most fundamental solution is to add an appropriate amount of a suitable solvent to the ink to reduce the viscosity of the ink. After the viscosity of the ink is reduced, the fine streamlined knife line will generally be eliminated. This is because the viscosity of the ink is lowered after the solvent is added, and the fluidity is accordingly increased. Therefore, it is necessary to pay attention to the fact that the fine streamlined blade line is degraded in fluidity.
The second type of line is the starting point of the printed pattern, but the lines are concentrated, and they are rough, and appear regularly in the same position of the print, often continuing to the next color. This kind of line is easily found. . The reason for this type of knife line is that the viscosity of the ink is too high, the printing plate's Internet point is poorly transferred, and the internal additives of the ink are destroyed with the change of the ambient temperature. Especially when the temperature is too high, a thin layer of ink will form on the surface. Dry solid layer, long time the ink layer accumulated between the printing plate and the squeegee will push up the squeegee, resulting in this knife line. To solve this kind of knife line method, first adjust the squeegee angle. Generally, the angle between the squeegee and the plate is 60°, but sometimes the angle between the squeegee and the plate can be increased to about 65°. Therefore, the pressure of the squeegee knife also increased accordingly. At the same time, an appropriate amount of the corresponding additive or solvent is added to the high viscosity ink to reduce the viscosity of the ink and increase the fluidity of the ink. When the solvent is added, the ink should be agitated along with the direction of the solvent. Another solution is to put the agitator in the ink tank; the roller, as the drum rotates, the agitating roller also rotates accordingly. There is a way to prevent the formation of ink on the surface, which is also a way to reduce the knife line. The above two solutions are used in conjunction with each other. In the absence of special circumstances, the above-mentioned concentration of knife lines will be effectively curbed. It must be stated that the angle of the squeegee should not be increased too much to prevent the damage of the brand roller. .
The relationship between the production of the knife line and the ink particle size The thickness of the ink particle is closely related to the production of the knife line. The finer the ink, the better the quality of the printed product, resulting in a corresponding reduction in the knife line and the probability. There are strict requirements on the size of the ink's grain size. Usually the ink's fineness is 15um. The ink's fineness will not meet the requirements. The rough particles will push the blade upwards, which will result in the knife line. At the same time, the too coarse ink particles will cause the blade and printing. The damage of the edition is very big, the thickness of the ink should be moderate, too thin and not good.
After long-term observation of such knife lines, it was found that the direction of the knife lines caused by the rough ink particles is not the same on the printed products, mainly in three forms. (To be continued)