The solution of angle swing in the hottest printin

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The solution of angle throwing in printing (Part 2)

the fibers in the paper will expand and deform after absorbing water. When the relatively dry paper is printed in the first color group, it will absorb more water, so the water content of the paper will increase greatly. When the second color is printed, the water content of the paper has increased a lot, and the water content provided by the printing unit has not changed significantly for a long time. Although the water content of the paper will be further increased, this relative increase is not as large as that in the first color printing. In other words, when the paper is printed in the second color, the size change is smaller than that of the first color. Of course, the relative deformation of the paper will gradually decrease after the third color

in the process of reducing pressure to produce money printing, the process of stress deformation is similar to that of water absorption deformation. The deformation of paper can be divided into elastic deformation and plastic deformation. During the first color printing, the paper will be deformed, and the plastic deformation cannot be recovered, and the elastic deformation of the paper and sheet will not have enough time to recover due to the high-speed printing. In this way, during the second color printing, the ink can only be transferred to the deformed paper, and another plastic deformation will occur on the paper, but the amount of deformation has been reduced due to the first color deformation; In the same way, the third color and subsequent color decks are the same, that is, the deformation of the paper is gradually reduced

2. angle swing caused by the printing press itself or during the use and adjustment of the machine

the manufacturing and structure of the machine itself and the operation adjustment of the printing machine can also cause angle swing failure. The pz4880-01a printing machine, which was originally produced in China, has a much more obvious angle swing. The reason is that the sinking of the tooth pad, uneven bite force and inconsistency easily lead to angle swing in the printing process. The paper in the industry will be pulled backward by the calendering force in the process of differentiation imprinting. If there is not enough force to maintain the stability of the paper, the paper is easy to produce relative slip on the imprinting cylinder during imprinting, and this slip will also be accumulated and amplified at the end of the paper, resulting in angle swing

III. remedial measures for paper deformation and machine adjustment

1. when selecting paper, select the corresponding paper according to the printing requirements. If printing requires accurate overprint, we should choose paper with low straw pulp content, high surface sizing and high mechanical strength when selecting paper. Secondly, the paper shall be subject to humidity control before printing (if possible, it is better to use forced humidity control to ensure that the paper has a relatively high water content), so as to stabilize the water content of the paper and improve the line stability during the printing process

2. for the angle swing fault caused by the machine itself, it can be adjusted from the following aspects:

① make the teeth of the first color group bite the paper normally, and the teeth of the two ends of the impression cylinder of groups 2-4 have a slightly smaller tooth force

② cushion less rubber blanket in groups 2-4 (about 0.05mm can be reduced). In this way, the paper that has been thrown can have some convergence, but this requires the operator to have a wealth of printing experience to master the scale

③ in addition, the tooth pads at both ends of the embossing cylinder can be increased, so that the higher part can first contact the pressure, so that the paper can be pulled slightly to converge in the two corners without diffusion

IV. the scheme adopted in the design of modern printing machines to solve the problem of angle swing in the printing process has been well solved by modern printing machines in China, such as:

① the teeth adopt the overall structure of high-strength alloy steel to ensure the stability of the paper and avoid double shadow and angle swing

② the back plate card is segmented to solve the phenomenon of "angle swing" in printing

③ multiple supporting screws are used on the supporting rod of the tooth pad of the impression cylinder to prevent the angle swing failure caused by the sinking of the tooth pad

2. several foreign printing machines also have different solutions. For example, the tooth shaft of the drum biting is designed to be bendable, and there is a pre bending action before biting the paper, which can be adjusted according to needs, so as to avoid the angle swing fault

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