1, the ink is dry on the layout
The ink remaining in the cell is affected by some factors (such as increased viscosity of the ink), and some of the ink is dried. When the plate cylinder enters the ink tank again, the ink solidified in the cell is difficult to be completely dissolved, and the ink is transferred. The rate will also decrease. Over time, the cells are blocked more and more shallow, the ink transfer rate is getting lower and lower, and finally the blockage failure is caused. Such blocking problems are related to factors such as ink type, viscosity, solvent, drying speed, printing speed, etc., and also have a great relationship with the structure of the printing press.
2, mixed with impurities in the ink
The gravure printing speed is relatively fast, and the printing substrate (film) often generates static electricity during high-speed operation. Due to the adsorption of static electricity, impurities such as debris falling off on the dust-printing substrate in the surrounding environment are carried into the ink. These mechanical impurities are the direct cause of blockage of the plate cells. In order to prevent such an accident, an 80-120 mesh metal mesh can be installed in front of the nozzle of the circulation pump to filter the ink to remove insoluble impurities.
3, low plate making quality
The gravure plate is subjected to multiple etching processes such as surface etching or engraving, aluminum plating, and grinding. In these processes, the smoothness of the inner wall of the cell, the burrs generated during grinding, and the omega-type cells due to corrosion or engraving all have a certain influence on the transfer rate of the ink. This causes the ink transfer rate to decrease, resulting in blockage.
4, poor ink dissolution (deterioration)
Poor ink flow, turbidity precipitation, or mixing of different inks due to incomplete cleaning after parking, and misuse of other poor solvents, etc., cause poor ink dissolution, and the transfer rate is lowered, which may cause blockage.
5, the chemical changes in the ink
With the continuation of the printing process, the two-liquid type ink or the reactive ink will gradually undergo chemical reactions such as cross-linking, which deteriorates the fluidity of the ink, increases the viscosity, and lowers the transfer rate, which may be the cause of blocking. Therefore, when using two-liquid type ink or reactive ink, wipe the plate in time after stopping, and use expired ink and residual ink with caution. In addition, the mixing of different types of inks may cause chemical reactions, resulting in blockages. Therefore, it is necessary to confirm in advance whether different types of inks can be mixed.
Second, blocking problem solving countermeasures
1. When a plastic gravure jam occurs, it should be cleaned with a solvent or a special cleaning agent, and the cause of the blockage should be solved separately.
2, the temperature and humidity of the printing workshop should be appropriate, the drying speed of the solvent must be compatible with the printing speed and printing environment.
3. The distance between the scraper and the impression cylinder should be as short as possible to prevent the hot air leaking from the drying box from blowing through the layout.
4. Mix and use slow drying solvent to increase the printing speed.
5. When there is a blockage failure caused by ink performance defects, the ink should be replaced in time (or contact with the ink supplier) to avoid the use of inks with significant differences in specific gravity.
6. The ink in the ink tank should be stirred frequently so that the ink in each part is in a flowing state. New inks should also be added or new inks should be replaced in time to avoid ink filming.
7. When there is a blockage caused by the quality problem of the inner wall of the printing plate, it should be re-plated or re-plated.
8. Before starting the machine or just starting up, you should first wipe the plate cylinder with solvent. In the printing process, it is necessary to avoid stopping in the middle of the road. For long time parking, the plate must be cleaned first, or the plate cylinder should be immersed in the ink tank for continuous idling.
9. In fresh ink, additives such as inks and wax substances may crystallize out due to temperature difference, etc. At this time, it is tried to warm the ink (40 to 50 ° C) before use to dissolve it.
10, solvent misuse, ink deterioration and mixing of different types of ink, etc., will significantly affect the re-solubility of the ink. Therefore, a regular special dilution solvent should be used. When replacing the ink, thoroughly clean the ink tank and circulation pump, then pour in new ink.
[Time: 2017-09-04 Source: Huayin Flexible Packaging]
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