Exclusion of "Heap Eraser" Fault in Offset Printing Production

"Heap rubber" is one of the common faults in offset printing production. When the blanket is just filled with ink, the imprinting of the printed matter is not clear and the dots are padded. When the accumulated material reaches a certain degree, the phenomenon of color shift and dirty printing will be caused, and the wear of the printing plate will be exacerbated. There are many factors that cause "rubber piles" and the methods of handling are different. The following reasons are analyzed.

1. The paper surface coating is not sticky and there is too much paper dust. The coating on the surface of the paper is unevenly coated or the sizing is insufficient. Under strong light, it can be clearly seen that the surface of the paper is rough or there are many paddles. For this kind of situation caused by the "rubber eraser" failure, in addition to adding the right amount of additives, but also without affecting the quality of the print under the appropriate circumstances to reduce the printing pressure, and reduce the speed during the printing process, in order to reduce the paper stripping to be solve. If conditions permit, the white material can be passed through the empty roller to remove paper and confetti on the surface of the paper. If the product allows, it will be better if the light paddle is passed through once.

2. One of the main reasons for stacking rubber is due to the high viscosity of the ink, which causes the fibers and paper powder on the surface of the paper to stick and pile up on the blanket. Solution: You can put appropriate additives or viscosity reducer in the ink to reduce the viscosity of the ink. The additive amount should be controlled so as not to affect the drying performance and gloss of the ink.

3 blanket surface crystallization, too smooth. The experimental comparison shows that the smooth surface of the blanket has a much greater adsorption capacity for the paper-bound impurities than the rougher blanket. Solution: Thoroughly clean the blanket to return to a fluffy surface, or choose a blanket with a slightly rougher surface for better results.

4. Ink emulsification is excessive. After the ink is emulsified, the pigment will separate from the floating state and remain on the blanket to cause a “stack of rubber” or to remain on the plate to cause “stacking”. It can be seen that the ink on the ink roller is sticky, and the ink is dull. By cleaning the ink roller, the viscosity of the ink can be appropriately reduced, and the ink balance can be adjusted and controlled to be solved.

5. The ink is drying too fast. When the ink layer of the unit ink roll is thin, after a period of time, the ink roller heats up and the drying speed of the ink is too fast. Since the viscosity of the ink is the strongest when it is dry, the transfer rate will decrease, and a pull-down phenomenon will occur, resulting in a phenomenon of “stack rubber”. Can be solved by the following ways: a. reduce the workshop temperature, so that the humidity is maintained at about 65%; b. add an appropriate amount of viscosity-reducing agent or anti-dripping agent in the ink.

6. The color sequence is not properly arranged. After the color group, the ink viscosity is greater than the pre-color group, and the post-color group inverts the ink in the pre-color group to cause accumulation, and severe color can also cause cross-coloring. By adjusting the color sequence and adjusting the viscosity of the ink, the viscosity of the ink in the back color group is slightly smaller than the viscosity of the ink in the front color group. (author/wuxing)

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