Brushing is one of the problems often encountered in gravure printing. Improper handling will affect the production and quality of flexible packaging products. Generally, the drawing phenomenon of black, cyan and magenta is more obvious, and generally appears on a large area of ​​shallow net.
1. Foreign objects stick to the blade edge or under the blade
You can move the squeegee back and forth, up and down during the printing process, remove the adhering foreign objects or use a bamboo stick to directly remove the squeegee blade ( must be completed by a skilled operator to avoid unnecessary losses due to improper operation ) , If necessary, stop the machine to thoroughly clean the doctor blade.
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Second, the ink circulation is not enough
Part of the ink is in the dead corner of the ink tank. The resin is not precipitated due to the lack of good circulation, forming crystals and agglomerates of different sizes, or excessive drying causes ink skin to form on the surface (in summer, it is easy to produce ink skin, spring and autumn due to temperature The influence of ink crystallization and agglomeration is more frequent ) . With the circulation of ink, a part of the ink crystal or ink skin is brought to the blade by the rotating plate cylinder, and the ink blade breaks it to form irregular drawing. Therefore, improvements must be made from the aspects of ink circulation and filtration.
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1. Cyclic improvement. Method one, tilt the ink tank left and right to ensure that the ink can be injected from the slightly higher end and flow out from the lower end to form a good circulation; method two, the ink tank should be placed flat, but the ink must be injected from both ends at the same time. Reflow in the middle, so that a good circulation can also be formed, and ink cannot be injected from one side.
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2. Improved filtering. The ink must be filtered for the first time before use. Even new ink should be filtered. Generally, a 140 mesh / inch filter screen is used.
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The method is to put a stocking under the ink outlet to form a filter bucket. After filtering for a period of time, if the filter is blocked and the ink flow is not smooth, you can insert some small holes with a bamboo stick above the bucket to increase the guide. Ink effect. The bottom of the bucket can also play a good role in depositing impurities.
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3. Ink fatigue
This kind of situation mostly happens when the printing area of ​​flexible packaging product printing plate is relatively small. During the printing process, the resin in the ink is continuously consumed. If the solvent is continuously added without adding new ink, the resin cannot be replenished, which changes the proportion of each component of the ink, causing ink fatigue and affecting normal use. The problem can be solved by adding new ink appropriately.
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Second, the drawing phenomenon caused by the printing plate
1. Surface treatment of printing plate
In the process of engraving gravure, many small burrs will be formed on the edge of the engraving mesh, and these small burrs will also damage the squeegee during the printing process, causing drawing. Generally, the new version is prone to this situation. Within a certain range, as the printing volume increases, the drawing will gradually decrease. This requires that in the process of making the plate cylinder, on the one hand, it is necessary to ensure that the hardness of the engraved copper layer is moderate, to reduce the formation of small burrs during the engraving process, and the copper layer must be treated after engraving; Polishing process. Grinding and polishing the surface of the printing plate can generally solve the drawing problem.
2. Installation of printing plate
If the printing plate of the flexible packaging product has a large circumferential beating during the printing process, it may also cause drawing. This requires checking the concentricity of the printing plate and the plate shaft (the center of the shaftless version is to be checked), whether the bearings and transmission parts are deformed, worn, or even the machine base is level.
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