Analysis of factors affecting the quality of flexographic printing products
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There are many factors affecting the quality of flexographic printing products, such as plate making, operating technology, equipment and materials, and so on. There are also many aspects in terms of ink. Flexographic printing uses more ink.
Water-based inks belong to Newtonian fluids, so the stability of inks is poor, mainly in the following three aspects:
1. Precipitation of ink pigments. Before use, the ink in the ink tank should be evenly stirred. When printing, the ink in the ink tank should be stirred frequently to prevent the color and standard of the print from being different due to the precipitation of the ink pigment. An effective way is to keep the ink in agitated and flowing state under the operation of the ink pump by means of a fully enclosed scraper.
2. During storage and use, the pH of the stabilizer is lowered due to volatilization of the ink component (it tends to be weakly alkaline). In the use of aqueous ink stabilizers are volatile, so that the ink tends to be weakly alkaline, resulting in increased surface tension, the adhesion to the surface of the printing plate is reduced, affecting the transfer performance and drying speed (the ink tends to be alkaline, dry The speed is accelerated), which will cause the printing and graphics to be incomplete during the printing process, especially when printing the screen version, because the ink is drying too fast, the printing dot is lost or the cable version is blocked.
3. In the use of ink, the viscosity of the ink increases due to the evaporation of moisture, and the flow performance is weakened. Some printing equipment supplies a single scraper system that requires a certain viscosity and fluidity to make it within a suitable range. When the ink is used and the fluidity exceeds the requirements for printing, the transfer performance of the ink is affected, and the "color difference" is printed on the surface of the printed matter.
Factors affecting the quality of flexographic products in terms of printed materials include the flatness of the surface of the printed material, the absorbency of the material, and the surface strength of the material.
The flatness of printed materials is a necessary prerequisite for the printing of large-area solid layouts. Due to the rough surface of some materials, the surface of the printed matter is obviously not printed. By increasing the printing pressure, although certain problems can be solved from the surface, the text content of the printed layout is blurred or the "edge effect" of the print is obvious.
Absorbency of materials For printing, the absorption of materials is advantageous. On the positive side, due to good absorption, the adhesion of the ink to the material is not easy to fall off; the disadvantage is that the absorption of the material is strong, resulting in an increase in the amount of ink used, such as the domestic oil-proof paper is particularly prominent.
The surface strength of the material is now used to print paper on the tray paper, the surface strength is poor, and the paper powder drops more, causing frequent rubbing during the printing process. In addition, the following are also factors that affect product quality issues:
1. If the printing plate design is light gray flat mesh, try to design a spot color in the design, avoid overprinting the yellow, red and blue primary colors, because it is difficult to control the gray balance.
2. The product structure type, such as large-area color block and blank part, a piece of blank in the field, which is inconsistent with the pressure, which will cause the plate roll to jump, which makes the printing part under pressure.
3. The configuration of the anilox roller is 600-700 lines in the printing mill's anilox roller. When producing 150-line products, 1% to 2% of the dots will be embedded in the anilox roller mesh, which affects the quality.
4. Ink solid content If the ink solid content is too low, in order to achieve a certain color density during printing, the number of anilox rolls must be reduced, which will slow down the drying speed of the ink, and if it is a cable version, it is easy to block.
5. Flatness of the printing plate If the flatness of the printing plate is poor, the pressure on the entire layout is inconsistent during printing. To ensure that the entire layout can be printed, there will be excessive pressure on some of the layout positions, and the outlets will be enlarged. is too big.
6. The anti-adhesive mesh of the anti-adhesive dot is not complete, which may result in poor ink transfer.
7. When the plate roll is too large, if the plate roll is too large, the plate roller is exposed to the air for too long after printing, and it is easy to block the plate.
8. The plate concentricity difference plate roller has poor concentricity, and the printing pressure is inconsistent.
9. Tension material tension control is related to overprinting problems, as well as the rate of scrapping after shutdown.
10. Raw material tension If the tension of the material is too large during rewinding, the overprinting position is serious during printing.
11. The choice of double-sided tape printing one product, only double-sided tape of the same density can be selected. If you do not use the same density double-sided tape, the overprint will be inaccurate due to the different amount of compression deformation during the plate.
12. The temperature and humidity of the workshop, such as high temperature and low humidity, are easy to block the plate; low temperature and high humidity will affect the drying.
13. Ink leveling property, such as poor ink leveling, leads to poor ink transfer and prints.
14. Oven drying capacity Oven drying ability affects the production speed. If the ink is poorly dried, the product will often lose its luster.
15. Dust on the surface of raw materials If there is more dust on the surface of the raw materials, it will stick to the printing plate during the printing process, so that white spots appear on the printed products, and some of them will be clogged with the printing plates and the anilox rollers. It will also hurt the squeegee.