1. Various reasons for wrinkling and wrinkling of paper in offset printing
1. The pressure of the pressure roller of the paper feeding table is not even
The paper is subjected to the axial force during the conveying process, which causes the paper to bulge in the middle during the positioning of the front stroke, forming wrinkles after imprinting.
2. The gripping force of the gripping cylinder of the impression cylinder varies
If the gripping force on both sides of the platen of the impression cylinder is insufficient, the trailing edge of the paper is wrinkled; if the gripping force on one side is insufficient, the corresponding trailing edge is wrinkled; if the gripping force in the middle is insufficient, the middle part of the paper Wrinkle.
3. Improper handover of paper
In the process of handing over the paper before imprinting, if improper cooperation causes the length of the paper at the edge of the grip to change, the trailing part is likely to wrinkle.
4. The unevenness of the dental pad
When the paper is gripped, if the pads are not flat, the edges of the paper will be wavy, and the grip will be partially wrinkled.
5. The position of the paper edge and gripper is inaccurate
After the paper is positioned, if the paper is gripped by the teeth a bit, the edge of the paper will be uneven and wrinkled.
6. The ink sticking on the surface of the impression cylinder is too thick
The thickness of the ink sticking on the surface of the impression cylinder is too thick, which makes the paper uneven when it is imprinted, and also produces local short-distance wrinkle deformation.
Paper cause
1. The trace of paper knocking is too deep and too dense
Because of the improper force of knocking paper, the traces of knocking paper are too deep and too dense, and wrinkles are easily generated at the folds of knocking paper during printing.
2. Paper thread direction
When the paper enters the machine for imprinting, if it is a straight thread, it will easily cause wrinkling.
3. Paper moisture content is too large
If the moisture content of the paper is too large, the fiber of the paper itself expands. During the imprinting process, the expanded fiber narrows from hypertrophy, and it is easy to produce branch-like wrinkles that extend from the mouth to the trailing direction.
4. The influence of environmental temperature and humidity
The temperature and humidity of the environment change, resulting in uneven water content of the paper. If the surrounding water content is greater than the middle, the ruffles are generated, and the paper is easy to wrinkle during printing.
Second, the effective solution of paper wrinkling in offset printing
After the wrinkle failure of the paper appears, it is necessary to take targeted measures to ensure printing efficiency and quality. For the wrinkles caused by the above reasons, the following measures can be taken to overcome them.
First, properly strike the printed sheets to improve the printability of the paper, so as to eliminate the wrinkling of the next color printing.
Second, adjust the gripper of the roller to make gripping force even, so that the printed sheet is in the proper position for gripping teeth, and eliminate the wrinkle failure caused by the misalignment of the paper.
Third, when imprinting, make sure that the paper is uniform and tightly attached to the impression cylinder.
In addition to mechanical reasons and the paper itself, improper use of the liner can also cause paper wrinkling. If the liner is too soft, convex or false, or the liner is not tight, it will cause the paper to wrinkle. Therefore, attention should be paid to the lining process to prevent wrinkling caused by loose lining.
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