How to get rid of the dirt problem

In the modern packaging and printing industry, many printing companies use flexographic or gravure printing. Rotational printing is the main method. To know the web printing materials used for rotary printing, it is easy to cause printing due to the absorption of dust and other impurities. Difficulties have led to a decline in the quality of printed products and an increase in scrap rates, thereby reducing customer satisfaction and product printing prices. In response to these problems, a series of measures to remove dust and other impurities were taken, as follows:

Since dust and other impurities are attached to the surface of the printing material by electrostatic adsorption, it is first necessary to eliminate the electric charge and cooperate with other corresponding measures in order to completely remove dust and other impurities and achieve the requirements of printing and other processing. After the printing material is treated with static electricity, it can avoid re-adsorption of dust and other impurities.

First, there are three ways to eliminate electrostatic charges:

1. Transfer electrons directly from printing materials

In the environment with high humidity, the substrate is directly grounded, and the electrostatic charge on the substrate can disappear, making it no longer retain high charge, and meet the printing process requirements.

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

Ionized air can also be used to eliminate the charge. It is achieved by mechanically spraying the ionized air in the working environment on the surface of the printing material. This device is called a charge ionization eliminator. Various shapes of needles or rods can be used as electrodes, and the ionized air stream of strong air is blown toward the surface of the printing material through a nozzle in the shape of a gun mouth.

3. Transfer electrons by contact with other materials

Charges that have been ionized, similar to conductors tend to discharge from objects charging. In this case, the use of fiber brushes, the use of helium, neon and other low-level elements and radiation generated by the ions in the surrounding air, you can neutralize the electrostatic charge surface of the printing material, but this method is only used for certain special occasions. Under normal circumstances, the direct current or AC high voltage can be used to neutralize the electrostatic charge on the surface of the substrate to eliminate the electrostatic effect.

Second, an effective method to remove dust and other impurities

The printing materials have to achieve an acceptable level of printing, not only to eliminate the electrostatic charge on the surface, but also to remove all the dust and other impurities adsorbed on the surface. After the charge is eliminated, the adsorption capacity of the printing material to dust can disappear immediately, and the dust in the surrounding environment can be prevented from being adsorbed again. However, this does not mean that the dust and other impurities that have been adsorbed on the surface have been removed, and therefore other measures must be used in conjunction with it. .

The easiest way is to remove the electrostatic charge and then use a brush to clean it. However, this method can only remove large particles and incomplete removal. A more effective method is to use an ultrasonic generator to generate a strong compressed air flow. Through the same width as the paper roll web and very close to the nozzle of the paper roll, the compressed air is blown to the surface of the printing material to produce an air knife-like effect to sweep the dust. . Its function is like a vacuum cleaner, dust will not return to the surface of printing materials. Although different nozzles of different brands have different geometrical profiles, they all use their own technology to make the air flow reach a very high speed. Some nozzles can generate airflow speeds of more than 560 kilometers per hour, which can effectively remove the adherence to the printing. Dust particles on the surface of the material.

Third, the method of removing special stains in printed products

It was found that the middle part of the print has a half-circle buoyant body, showing a variety of shades of red, yellow, blue, and green. Wiping the plate with wet powder did not work. There was oil on the presser foot, which caused dirt on the plate, so wipe the presser foot and mouthpiece with a cloth, and the stain remained. The blade was also used to scratch the surface of the plate, rubbed with a corroding rod, and then etched with phosphoric acid to open the ink and stains. Suspected that there is a relationship with the plate, changed the new version, still dirty. Since the position of the stain is consistent with the position of the presser foot press, which is related to the presser foot, the presser foot was inspected and it was found that the copper of the presser foot was not the same as in the past and there was no other abnormality. Is it related to copper? In the past, the presser foot was made of brass. Now it is replaced by a red copper product. The difference between the two is that the red copper has a soft texture. The brass-made presser foot was replaced with brass, and the layout was reprocessed. When the ink was reprinted, the stain was eliminated.

Why does this happen? We think that it may be due to the soft texture of red copper. The rough paper in the printing grinds down some fine particles. After being brought into the printing plate by paper, it is affected by other factors and a chemical reaction occurs. As a result, this obstinate stain appears.