Conglutination in printing and the reason

In the printing process, we will often encounter the phenomenon of paste, which refers to the expansion and deformation of the dark tone dots of the layout, merging with each other, so that the dark tone level is gone, and a fuzzy mark is formed on the printed product, which is seriously formed Due to dirty spots, the main reasons for the paste version are as follows.

1. Caused by excessive ink supply and poor printing adaptability of ink

â‘  The amount of ink supply is too large, which causes the ink layer accumulated on the layout to be too thick. Under the action of printing pressure, a graphic dot spread is generated, and the lines are thickened without edges, resulting in paste.

â‘¡ The ink is too thin, and the fluidity is large, causing dot spreading to cause paste.

â‘¢ Excessive dry oil in the ink will make the ink emulsified and increase, so that the ink layer on the printing plate cannot be broken from the middle, and most of it stays on the printing plate, causing ink accumulation. Under the action of the squeezing force of the roller, the dots are gradually expanded , Resulting in paste, excessive desiccant will increase the viscosity of the ink, the adhesion of the blank part is enhanced, it is easy to make the dark tone part of the printed product cause paste.

â‘£In daily work, if we use too much ink or tackifier, it will increase the oiliness of the ink. During the printing process, the boundary between the dots in the picture and text will be blurred and cause paste.

Solution:

According to the graphic elements of the printed matter, properly control the amount of ink supply, control the amount of dry oil, ink adjustment oil and debonding agent. When using strong oily ink, increase the acidity of the wetting fluid appropriately.

2. Confusion caused by insufficient water supply

Because the pressure between the water roller and the plate cylinder is too small; the surface of the water roller fleece is dirty; the water roller is too long to use and the fluff loses its elasticity; during printing, the water roller sleeve at the place where there are many elements on the printing plate is worn Relatively serious, the water absorption at this place is also relatively poor, and the water supply is insufficient due to other reasons. The loss of water and ink balance during the printing process leads to paste.

Solution:

â‘ According to the workload and the degree of use of the water roller, replace the water roller sleeve in a timely manner.

â‘¡ Use a perforated beverage bottle to fill the bottle with moistening liquid, and spray water to the place where the water roller is seriously worn. This can reduce the number of times to replace the water roller sleeve and reduce the paste version. Point, but very practical.

Third, the blanket is stretched too loose or printing pressure caused by excessive pressure

If the blanket is too loose, it will squeeze and distort greatly during the printing process, which may easily cause paste. Excessive printing pressure not only aggravates the abrasion of the printing plate, but also directly increases the spread of the graphic ink layer, resulting in paste.

Solution:

When changing the rubber cloth, it should be properly tightened, and the pressure of the printing cylinder should be adjusted before printing, so as to reduce paste.

Fourth, paste plates caused by severe plate wear

The area of ​​the oleophilic picture and text on the dark tone of the printing plate is much larger than that of the hydrophilic blank part. Once the blank part of the blank part is worn, it will cause the hydrophilicity to weaken, and it is easy to be invaded and spread by the surrounding ink, resulting in paste. phenomenon.

Solution:

â‘  Adjust the pressure between the rollers to avoid excessive pressure, causing the plate to wear.

â‘¡Don't collide and rub the printing plate during the process of transporting the printing plate and loading the plate.

5. Paste caused by the weakening of the acidity of the wetting fluid

During the printing process, the alkaline paper wool and paper powder will be transferred to the water hopper, neutralizing the acidic wetting liquid, weakening the acidity of the wetting liquid, and the phosphoric acid or citric acid in the wetting liquid will stain the plate surface It has a cleaning effect, the acidity of the wetting liquid is too weak, the cleaning ability of the oil stain on the plate surface is insufficient, and it is easy to paste the plate when printing the oily ink.

Solution:

â‘  Change the water in the water bucket regularly.

â‘¡If the paper used for printing is qualified, it is best to blow it with a paper dryer. In this way, the impurities, paper wool and paper powder contained in the paper can be blown off, and the moisture content of the paper can be evenly and uniformly ensured. The moisture content of the paper is balanced with the temperature and humidity of the printing workshop, so that the hysteresis of the paper occurs before printing, which reduces the sensitivity of the paper to water, so that the paper adapts to the temperature and humidity of the printing workshop before printing, so that the entire printing process can Done successfully.

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