Causes of paper creases and wrinkles in offset printing

First, offset printing, paper wrinkling, wrinkled a variety of reasons

1. The pressure on the paper transfer roller is uneven

The paper is subjected to axial forces during the transfer process, causing the paper to bulge in the middle when the paper is positioned in advance, forming wrinkles after imprinting.

2. The pressure of the impression cylinder grips the teeth

If the pressure on both sides of the impression cylinder grips the row of teeth, then the wrinkling of the paper is wrinkled; if the side of the pressing force is insufficient, the corresponding trailing edge wrinkles; if the intermediate pressure is insufficient, the middle part of the paper is Wrinkle.

3. Improper paper transfer

In the process of transferring paper before embossing, if the fit is improper and the length of the paper on the crepe is changed, the wrinkle is likely to wrinkle.

4. The tooth pad is uneven

When the paper is choked, if the pad is not flat, the edges of the paper will be wavy and the creases will partially wrinkle.

5. Inaccurate position of paper edge and tooth decay

After the paper is positioned, if the paper is pinched by the tusks, the paper edge is uneven and wrinkles occur.

6. The ink on the surface of the impression roller is too thick

The thick ink sticking on the surface of the impression cylinder makes the paper uneven when it is imprinted, and it also produces local short-distance wrinkling and deformation.

Paper reason

1. Tap the paper mark too deep, too dense

Because of the improper use of the paper, the paper traces are too deep and too dense. When printing, the creases of the paper are easily creased.

2. The direction of the paper silk

When the paper enters the machine, if it is a straight wire, it will easily cause the wire to wrinkle.

3. The paper has too much moisture

If the moisture content of the paper is too large, the fibers of the paper itself will expand. During the imprinting process, the expanded fibers will be narrowed due to the enlargement, and the dendritic creases tend to extend toward the direction of the dragging.

4. Influence of ambient temperature and humidity

Temperature and humidity changes in the environment, resulting in uneven moisture content of the paper, such as the surrounding water content greater than the middle, resulting in lotus leaf edge, printing paper wrinkles.

Second, offset printing paper wrinkling effective solution

After the wrinkling problem of the paper is raised, measures must be taken in a targeted manner so that printing efficiency and quality can be guaranteed. For wrinkles caused by the above reasons, the following measures can be taken to overcome them.

First, the printing sheet should be appropriately processed to improve the printability of the paper so as to eliminate the wrinkles of the next color printing.

Second, adjust the roller cavities to make their force evenly, so that the printed sheets are in the correct position of the cavities, eliminating the wrinkle failure caused by the paper transfer misalignment.

Third, when imprinting, ensure that the paper is flat and close to the impression cylinder.

In addition to mechanical reasons and the paper itself, improper use of liners can also cause paper wrinkles. If the lining is too soft, there are bumps, inconvenient conditions, or the lining is not tight, it will cause the paper to wrinkle. Therefore, you should also pay attention to the lining process to prevent wrinkling caused by loose packing.