Paper offset process stack failure
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In the offset printing process, due to the sizing pore structure, smoothness, absorbency, viscoelasticity, etc. of the paper, the filler, rubber compound and colorant particles are rough in the papermaking process, and the appearance quality of the paper is dust, spots, fiber clusters, sand grains, etc. Poor quality, often resulting in heap failures. There are many reasons for the stacking. This article mainly talks about: paper hair removal, paper powder removal, pile paper wool on blanket, paper ash. The reasons for the paper stack are different and the solution is different.
1, paper hair removal stack
The failure of the paper pile in the offset printing process is mainly caused by the paper hair removal caused by the loose fiber structure on the paper surface. This phenomenon is mainly caused by the poor printing quality of the paper, and the failure is manifested by the paper surface of the imprinted ink. Whitening phenomenon, the paper hair falling off causes the printing plate and the surface of the blanket to be covered with paper wool. In severe cases, it is necessary to wipe the printing plate and the rubber once for every 1000 sheets printed, which causes printing quality problems and delays production progress and delivery time.
The hair removal on the front and back of the paper is a technical problem in the papermaking raw materials and papermaking process. Offset printing is an indirect printing using an intermediate elastomer blanket cylinder. The printing plate transfers the image to the blanket cylinder. The blanket cylinder is transferred to the printing paper by the impression cylinder. The paper is printed during the offset printing process. It will be transferred from the surface of the blanket to the printing plate. As the number of printing increases, the paper hair remaining on the surface of the printing plate will accumulate more and more, causing the failure of the paper pile and the paper hair will stick to it. The printing plate is printed on the surface, thus affecting the quality of the printed product.
The fiber paper and paper ash on the paper have both water absorption and oil absorption. When the paper is absorbed on the printing plate, as the plate cylinder is transferred, it first hits the water roller to wet, and the water roller is at the same time. There is a certain pressure on the printing plate. After the paper hair is wetted and pressurized by the water roller, most of it is attached to the printing plate and then inked by the ink roller. At this time, the wetted paper wool is oil-repellent, and although the ink is not absorbed by the four inking rollers, the whitening phenomenon occurs when the transfer to the blanket is performed.
Solution:
(1) Master the ink and water balance during offset printing, reduce the moisture of the layout and reduce the pressure of the water roller on the printing plate without the dirty version. The purpose is to minimize the wetting of the paper on the surface of the printing plate, thereby reducing the oil resistance of the paper and increasing the ink force, and try not to stick it to the plate.
(2) Increasing the fluidity and viscosity of the ink, adding a small amount of varnish, printing the product with less ink, and correspondingly increasing the pressure of the ink roller on the surface of the printing plate, the purpose of which is to pass the paper on the printing plate. When the inking roller is inked, the paper hair is pulled out and transferred to the ink roller, which is mainly accumulated on the ink roller.
In addition, adjust the printing suitability of the ink, and add the varnish and auxiliary materials repeatedly and evenly. It is also possible to appropriately increase the amount of ink in the ink fountain to solve the problem.
2, paper powder off the stack
The pile surface of the paper surface is powdery and full of honeycombs. It is caused by the loss of countless fillers, rubber materials, color materials and auxiliary materials. It seriously affects the quality of printed products. It needs to be scrubbed once every 1000 sheets. The reason for the formation is similar to that of paper paper piles, but there are differences in the solutions. The proportion of paper wool and powder is different, the paper wool area is large and light, and the powder is extremely fine and heavy.
Solution:
Increase the fluidity of the ink, add a thinner varnish in the ink, increase the viscosity and ink volume of the ink, increase the ink storage on the ink roller, and deepen the ink color of the ink. In addition, the pad can be added under the printing plate. The thickness of the paper increases the printing pressure.
3, pile of paper wool, paper ash on the blanket
Mainly due to the manufacturing process of the paper, the paper may be loosened and fluffed during the printing process, and accumulated on the blanket, which affects the ink dot of the imprinted ink, the correct transmission of the text, and the paper ash and paper powder on the paper. It will pass through the rubber and plate cylinder and pass through the ink roller to the inside of the ink fountain. This will affect the transmission of the ink path. When the paper is damaged, the paper will be printed with paper dust, paper wool and paper powder. At this time, the amount of ink is turned to the maximum, and the ink color of the print is also light and revealing. When 1000 sheets of white paper are printed on the blanket, the blanket needs to be scrubbed.
Solution
(1) Wash the blanket with diligence.
(2) Before printing the paper, apply a white oil and water to make up for the lack of powder removal. White oil is a white translucent emulsion. It can dilute the ink color, reduce the viscosity of the ink, and evenly match the color. It is composed of magnesium carbonate, stearic acid, water, dry vegetable oil, etc. It is mainly used to set the white oil to make a base and reduce the phenomenon of powder removal and pulling of paper.
(3) Add a small amount of debonding agent to the ink, and do not add the smooth paper with good smoothness. Do not overdo it, and the dosage should not exceed 3%.
(4) Add 0.05 mm thick liner paper to the blanket cylinder, or adjust the center distance to increase the printing pressure.