"Stacking rubber" is one of the common faults in the production of offset printing. When ink is just piled up on the blanket, the printed product is not clearly printed, and the dots are sparse; when stacked to a certain extent, it will cause color deviation and dirty plate phenomenon, and increase the wear of the printing plate. There are many factors that cause "piling rubber", and the treatment methods are also different. The following will analyze each cause.
1. The coating on the surface of the paper is not firmly adhered, and there is too much paper powder. The coating on the paper surface is uneven or the sizing is insufficient. Under strong light, the surface of the paper can be clearly seen as rough or with many paddles. For the "rubber pile" failure caused by this situation, in addition to adding an appropriate amount of additives, it can also appropriately reduce the printing pressure without affecting the quality of the printing, and slow down the speed of the vehicle during the printing process to reduce paper peeling. solve. If conditions permit, you can first pass the white material through the empty roller to remove some paper wool and paper dust on the surface of the paper. If the product allows, it is better to go through the bright paddle first.
2. One of the main reasons for stacking rubber is due to the high viscosity of the ink, which sticks the fibers and paper powder on the surface of the paper and piles up on the blanket. Solution: You can put an appropriate amount of additives or viscosity reducers in the ink to reduce the viscosity of the ink. The amount of additives should be controlled to avoid affecting the drying performance and gloss of the ink.
3. The surface of the blanket is crystallized and is too smooth. Through experimental comparison, the smooth surface of the rubber cloth has a much stronger adsorption force for paper wool impurities than the rough rubber cloth. Solution: Wash the blanket thoroughly to restore the surface of the fluff, or choose a blanket with a slightly rougher surface to get better results.
4. Ink is too emulsified. After the ink is emulsified, the pigment will separate from the floating state and stay on the blanket to cause "stacking of rubber" or stay on the printing plate to cause "stacking". It can be seen that the ink on the ink roller is sticky and granular, and the ink is matt. It can be solved by cleaning the ink roller, appropriately reducing the viscosity of the ink, and readjusting and controlling the water and ink balance.
5. The drying speed of the ink is too fast. When the ink layer on the ink roller of the unit is thin, after a period of printing, the ink roller generates heat, which makes the drying speed of the ink too fast. Because the viscosity of the ink is the strongest when it is dried, the transfer rate drops, and the pull-back phenomenon will occur, thereby causing the "rubber pile" phenomenon. It can be solved by the following ways: a. Reduce the workshop temperature to keep the humidity at about 65%; b. Add an appropriate amount of viscosity reducer or desiccant to the ink.
6. Improper arrangement of color order. The ink viscosity of the back color group is greater than that of the front color group, and the back color group pulls down the ink of the front color group to cause accumulation, and in serious cases will also cause cross color. It can be solved by adjusting the color sequence and adjusting the viscosity of the ink so that the viscosity of the ink of the rear color group is slightly smaller than the viscosity of the ink of the front color group.
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