Troubleshooting of three types of paper offset printing

In the offset printing process, due to the paper's sizing pore structure, smoothness, absorption, viscoelasticity, etc., the paper is filled with filler, rubber, and pigment particles in the papermaking process. The appearance quality of the paper includes dust, spots, fiber clusters, sand particles, etc. The quality is poor and stack failures often occur. The main reasons for stacking are: paper dehairing, paper deinking, blanket piles, and paper dust. The reasons for paper stacking are different and the solution is different.

1, paper hair removal

During the offset printing process, the occurrence of paper stacking failures is mainly caused by the paper unwrapping caused by loose fiber structure on the surface of the paper. This phenomenon is mainly due to the poor printing quality of the paper, and the fault surface is imprinted with ink on the surface. With the phenomenon of graying, the surface of the printing plate and rubber blanket is covered with paper with the loss of paper wool. In case of severe printing, the printing plate and the eraser need to be scrubbed once for every 1,000 sheets printed, thereby causing print quality problems and delaying the production schedule and delivery time.

Paper positive and negative hair removal is a technical problem in papermaking raw materials and papermaking process. Offset printing is indirect printing using an intermediate elastomer rubber blanket. The printing plate transfers the graphic to the blanket cylinder. The blanket cylinder is transferred to the blanket cylinder. In a printing process on printing paper, during the offset printing process, the paper wool will be transferred from the surface of the blanket to the printing plate. As the number of printing increases, the amount of paper hair remaining on the surface of the printing plate will also increase. As a result of the failure of paper stacking, these papers stick to the surface of the printing plate, which affects the quality of the printed matter.

The paper fiber paper and paper ash on paper have both water absorption and oil absorption. When the printing plate absorbs the paper, after the plate cylinder transfers, it first encounters the water roller and the water roller is wet. There is a certain pressure on the printing plate. After the paper wool is wetted and pressed by the water roller, most of the printings are closely attached to the printing plate graphic, and then the ink roller is applied with ink. At this time, the moistened paper has oil repellency. Although the ink is absorbed by the four ink rollers, the ink cannot be absorbed, and the ink is transferred to the blanket and appears white.

Solution:

(1) Grasp the balance of water and ink during offset printing. Under the premise of a dirty version, reduce the water content on the layout and reduce the pressure of the water roller on the plate layout. The purpose is to minimize the wetting of the paper on the surface of the printing plate so as to reduce the oil resistance of the paper and increase the ink strength, and try not to cling to the surface of the plate.

(2) Increase the fluidity and viscosity of the ink, add a small amount of varnish, print the product with less ink, and increase the pressure of the ink roller on the plate surface. The purpose is to pass the paper on the plate. When the ink roller is inked, the paper is pulled out and transferred to the ink roller, mainly accumulating on the ink roller.

In addition, adjust the printing adaptability of the ink, and add the ink-changing oil and auxiliary materials to be mixed repeatedly. You can also increase the amount of ink in the ink fountain to solve the problem.

2, paper de-powderation

The surface of the paper produced by the deinking of the paper surface presents a honeycomb-like starry sky, which is caused by the shedding of countless fillers, rubber materials, color materials, and auxiliary materials. This seriously affects the quality of the printed product, and printing of about 1,000 sheets requires scrubbing a printing plate once. The reason for this is similar to that of paper piles, but there are differences in solutions. The proportions of paper and silty are different, and the paper area is light and heavy, and the powder is very fine and heavy.

Solution:

Increase the fluidity of the ink, add more dilute ink in the ink, increase the viscosity of the ink and the amount of ink, increase the ink storage on the ink roller, make the ink deeper, and increase the pad below the plate. The thickness of the paper increases the printing pressure.

3, pile of paper on the blanket

Paper gray main petroleum paper in the manufacturing process reasons, in the printing process may appear paper stripping off hair, and piled up on the blanket, affecting the blotted ink dot, the correct transmission of images, paper on the paper gray, paper The powder passes through the eraser and the plate cylinder, passes through the ink roller and enters the ink tank groove, affecting the transmission of the ink path, and encounters the paper with heavy powder. The ink is printed in the ink fountain and the paper is completely printed. Paper powder, at this time the amount of ink to the maximum, imprinted ink also appears shallow and light, printed on 1,000 sheets of white paper adhered to the blanket, you need to scrub the blanket.

Solution:

(1) Wash the blanket.

(2) Prior to the official printing of paper, a white oil and clear water are overprinted to make up for the lack of paper removal and lint removal. (White oil is a white translucent emulsion. Using it to dilute the ink color, can reduce the viscosity of the ink, the color uniformity Consisting of magnesium carbonate, stearic acid, water, dry vegetable oil, etc., it is mainly used to coat white oil to make a bottom and reduce the phenomenon of paper depowdering and pulling.

(3) Add a small amount of retreating agent to the ink. Do not add smooth and smooth coated paper. Do not overdo it. The amount should not exceed 3%.

(4) Add 0.05mm thick liner paper in the blanket cylinder, or adjust the center distance to increase the printing pressure.

Source: China Ink Technology Network