How to get rid of the problem of printing impuriti

2022-08-16
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How to get rid of the problem of printing impurities and dirt

in the modern packaging and printing industry, many printing companies, whether flexo printing or gravure printing, mainly use rotary printing. You should know that the drum printing material used in rotary printing is easy to cause printing difficulties due to the adsorption of impurities such as dust, which leads to the decline of the quality of printing products, increases the scrap rate, and thus reduces customer satisfaction and product printing quotation. In response to these problems, a series of measures to remove dust and other impurities have been taken, as follows:

because dust and other impurities are attached to the surface of printing materials by electrostatic adsorption, the charge must be removed first, and other corresponding measures must be taken to completely remove dust and other impurities to meet the requirements of printing and other processing. After electrostatic treatment, the printing material can avoid absorbing dust and other impurities again

first, there are three ways to eliminate the electrostatic charge:

1. Transfer the electrons directly from the printing material

in a high humidity environment, directly ground the printing material, and the electrostatic charge on the printing material can disappear, so that it no longer retains high charge, which meets the requirements of the printing process

2. Transfer electrons by contacting with ions in the surrounding air

ionized air can also be used to eliminate charges. It achieves its purpose by spraying ionized air in the working environment on the surface of printing materials mechanically. This device is called charge ionization eliminator, which can use needles or rods of various shapes as electrodes, and the ionized air is blown to the surface of the printing material through a muzzle shaped nozzle

3. Transfer electrons through contact with other materials

ionized charges, similar to the tendency of conductors to charge and discharge objects. In this case, using a fiber brush, polonium, iridium and other low-energy elements can produce radiation with the ions in the surrounding air to neutralize the electrostatic charge on the surface of the substrate, but this method is only used in some special occasions. Usually, DC or AC high voltage can be used to neutralize the electrostatic charge on the surface of the substrate to eliminate the electrostatic effect

II. Effective methods to remove dust and other impurities

in order to achieve an acceptable level of printing, the printing material requires not only to eliminate the electrostatic charge on its surface, but also to remove all dust and other impurities adsorbed on the surface. After the charge is removed, the dust adsorption capacity of the printing material can disappear immediately, and the dust in the surrounding environment can be avoided from being adsorbed again. However, this does not mean that the dust and other impurities adsorbed on its surface have been removed, so other measures must be taken together

second, the easiest way to find out the problem is to clean with a brush immediately after eliminating the electrostatic charge. However, this method can only remove larger particles, which is not complete. The more effective method is to use the ultrasonic generator to generate a strong compressed air flow, and blow the compressed air to the surface of the printing material through the nozzle with the same width as the paper roll and very close to the paper roll, which is similar to the role of the air knife, sweeping 50kN to complete the dust removal. Its function is like a vacuum cleaner, and the dust will not return to the surface of the substrate. Although different brands of nozzles have different geometric contours, they all use their own technology to make the air flow reach a very high speed. The air flow speed generated by some nozzles can reach more than 560 kilometers per hour, which can effectively remove the dust particles attached to the surface of the substrate material

III. methods for removing special dirt in prints

it was found that there was a half round floating dirt between them in the middle of the trailer tip of the print, which was red, yellow, blue and green. Wipe the printing plate with wetting powder, and there is no effect. It was thought that there was oil on the presser foot, which caused the dirt on the previous version, so wipe the presser foot and the blowing nozzle with a cloth, and the dirt remained. Scrape the position of dirty marks on the layout with a blade, polish with a corrosion rod, and then corrode with phosphoric acid. When printing, dirty marks appear again. It is suspected that it has something to do with the plate. After changing the new version, the dirt is still on. Since the position of the dirty mark is consistent with the position of the presser foot presser paper, it indicates that it is related to the presser foot, so the presser foot is checked and found that there are no other abnormalities except that the copper of the presser foot is different from the past. Is it related to copper? The presser foot used in the past was made of brass, but now it is made of red copper. The area counting probe of the two is set at the position of the corresponding transmission mechanism, especially the red copper is soft. Replace the red copper presser foot with brass, reprocess the layout, and the dirt was eliminated during reprint

why does this happen? We believe that it may be because the red copper is soft, and some fine particles are worn down by rough paper during printing. After being brought into the printing plate by paper, it is affected by other factors, resulting in chemical reactions. Therefore, this stubborn dirt appears

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