Paper printing powder problem
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Print off the powder. In the printing, due to the external force, the paper surface coating, fiber or dust is pulled up by the blanket, or the impurities in the ink path are transferred to the blanket, which causes the local graphic to be transferred to the paper normally, which seriously affects the quality of the finished product. a printing phenomenon.
In offset printing, printing off powder is one of the many quality problems that are easy to occur. It has caused great troubles for printing factories and paper mills. For this reason, printing and paper mills are doing how to avoid the occurrence of powder falling. A lot of work, but it can not be completely eliminated from paper and printing.
How to deal with the occurrence of powder? From the perspective of the paper mill, we have taken a number of measures in the production process to avoid the occurrence of powder, such as improving the surface strength of the paper and increasing the vacuum cleaner of the winder. Improve the cutting frequency of the cutter, etc., and achieved good results.
From the printing factory, how can we reduce the printing and processing conditions and conditions to reduce and avoid the problem of powder falling? Through our years of experience in handling customer complaints, and communication with customers, respectively In view of the problem of powder drop in different states, it is summarized from the cause of occurrence and how to take remedial measures from the printing process after the powder is dropped. I hope that it can be shared with the printing factory, and please correct me.
First define two nouns: the original point and the transfer point. The original point is the spot on the first sheet of the powder that has the powder problem, and there is no ink in between; and the transfer point is the spot produced on the subsequent print, which is in the shape of an irregular ring with ink in the middle.
Catheter section
The conduit section is a non-fibrous material that cannot be completely removed from the pulp. It is brittle and hard, and has a relatively small bonding force with the fiber and the coating. When subjected to external forces, it is relatively easy to be pulled up. His appearance is relatively regular, with an irregular rectangle or square, and the size is about 1mm.
In printing, if it is found that the powder form on the printed matter is a conduit section, the following methods may be adopted, which may be improved:
● reduce the viscosity of the corresponding ink;
● reduce the printing speed;
● increase the frequency of cleaning blankets;
● Replace the new blanket;
● Reduce the printing pressure of the pink sequence and increase the printing pressure of the front color sequence;
● First print the base paper with varnish, stick the tube section, and then print normally.
2. Remove powder
The powder removal is due to the coating between the paper surfaces. The lack of bonding between the coating and the fiber, a powder falling phenomenon that occurs when the coating is pulled up during printing. Its state is irregular .
The reason for this type of powder drop may be related to the lack of surface strength from the paper side; from the printing point of view, it may be related to factors such as excessive viscosity of the ink, excessive printing pressure, and too fast printing speed.
The phenomenon of powder falling such as powder removal may occur, and the method of treating the type of the tube section as described above may be adopted, and there may be a certain degree of improvement.
3. Paper paper powder
If the paper paper powder is adhered to the surface of the paper, it will adhere to the blanket during printing, and the image portion will not be transferred to the surface of the paper normally, forming spots, and the shape is irregular fiber.
The reason for the paper wool powder is mainly due to the fact that the cutting knife is relatively blunt, and the cutting is not caused by cutting the fiber but breaking it, and at the same time pulling some of the fibers out onto the paper surface. Under normal circumstances, such falling powder appears on the four sides of the printed matter, and the drag is the most serious. To determine if the paper has paper powder, use a dry black rag to wipe the surface of the paper, and then see if there is white powder on it. If it is, it means that there is paper powder on the paper, otherwise it is not.
It is found that there is paper paper powder in the paper, and it can be printed on the monochrome machine first, the paper paper powder is glued off, and then the printing is normal, which will greatly improve. If the printing factory is cutting itself, it is necessary to shorten the grinding cycle and avoid the generation of paper powder.
4. Ink skin
If the ink is dry and crust. Foreign matter or water system in the ink is contaminated to produce foreign matter, which adheres to the printing plate or blanket during the printing process, and also causes spots on the printed matter. On this kind of powder-off printed matter, the original point was not found, the paper coating was not destroyed, and the spots were all in the shape of a transfer point. For such powder drop, the ink path and water path must be thoroughly cleaned, including the ink tank sink and the transfer roller group water transfer roller set. Plate and blanket, then replace with new ink and fountain solution.
For the above types of powder drop, if it is impossible to accurately determine which type depends on the spot shape on the printed product, you can also use the transparent tape to stick the foreign matter on the blanket, and observe and analyze its shape and composition under the microscope. Confirm the specific cause, and take corresponding countermeasures for different types to reduce the occurrence of powder loss and minimize the loss.