The level of printing plate durability is directly related to the economic benefits of production, and it is also an important condition for reducing production costs, increasing output, and ensuring printing quality. Influencing factors of gravure ink and environment on the durability of the plate cylinder mainly include: the viscosity and drying speed of the ink, impurities such as hard sand, dust, ink erosion, and the causes of chemical factors. The following is an analysis of these factors.
1. The viscosity and drying speed of the ink
In order to scrape off the excess ink from the surface of the plate cylinder, the doctor blade must penetrate the ink film. Therefore, when the ink viscosity is large, a large doctor blade pressure is required. Therefore, the viscosity of the ink should be reduced as much as possible in order to reduce the pressure of the scraper.
In addition, the ink is dried too much, and the friction between the plate cylinder and the doctor blade is relatively increased, which also has a certain impact on the life of the plate cylinder. In addition, when the environment is too wet, the ink dispersibility becomes poor, and the plate cylinder is not easily scraped. Therefore, the pressure of the scraper has to be increased accordingly, which increases the friction of the scraper against the plate cylinder.
2. The influence of impurities such as hard sand and dust
If there are hard particles in the ink, the plate cylinder is easily scratched by the hard particles when scraping the ink. The lighter ones will affect the quality of the printing, and the heavy ones will cause the plate cylinders to be scrapped. In addition, the impurities on the surface of the substrate are also easily mixed into the ink, which accumulates too much over time and easily damages the plate cylinder, so it is often necessary to keep the substrate and ink clean as long as possible. In order to remove foreign materials, you can filter the ink in the ink tank regularly or insert a wire mesh into the ink reincarnation system to continuously filter. Whether the dust in the environment falls into the ink or is adsorbed on the impression cylinder, it will directly damage the blade and the plate.
Impure substances, coarse particles, foreign matter, etc. in the ink are mainly caused by the following factors:
(1) Coarse particles can be generated when foreign matter mixed in the ink or the auxiliary agent in the ink precipitates with temperature change and the pigment aggregates.
(2) Some foreign objects are brought in by the film. When the film adsorbs dust and additives in the film due to static electricity, and enters the ink, foreign substances are formed. Especially when the workshop is too dry, the film easily absorbs dust due to static electricity, which in turn causes an impact on the life of the plate cylinder.
(3) When a pigment with high hardness is used, even if it is mixed, it may cause a knife line. If the pigments used in red and blue inks are difficult to grind, they are relatively prone to cutting.
(4) The drying system sucks the dust in the outside air or the air duct is not cleaned for a long time.
3. The aggressiveness of the ink
Some inks, such as black ink, are aggressive to the plate cylinder, so they should be cleaned in time after use.
4. Chemical factors
A certain amount of active agent is added in the production process of the ink. If the activity of the ink or the plate cylinder is too high, the active substance will adhere to the plate cylinder more firmly during the printing process, and the scraper is difficult to completely scrape off. This has to increase the blade pressure, which in turn affects the life of the plate cylinder. At this time, the plate cylinder can be cleaned, and after removing the active substances that have adhered to the plate cylinder, adding a special surface activity retarder to the ink will achieve a significant effect. If the surface active agent is added before printing, it can play a preventive role.
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