In the process of offset printing, sometimes there will be a phenomenon of paper creasing. So what is the reason for the wrinkling of the paper in custom hard-cover book&soft-cover book printing?

First, the cause of wrinkles

1. The pressure of the paper wheel on the paper feed table is uneven

The paper is subjected to axial forces during the transfer process, which causes the paper to bulge in the middle of the front position and form wrinkles after embossed.

2. Improper handover of paper

In the process of paper handover before stamping, if the improper combination causes the length of the paper to change, the drag tip part is easy to wrinkle.

3. The holding force of the paper teeth of the embossing drum varies

If the clamping force on both sides of the paper teeth row is insufficient, the drag tip of the paper will wrinkle; If the holding force of one side is insufficient, the corresponding drag tip edge will wrinkle; If the holding force in the middle is insufficient, the middle part of the paper will wrinkle.

4, the position of the paper edge and teeth is not accurate

After the paper is positioned, if the paper is caught a bit by the teeth, the edge of the paper is uneven and wrinkled.

5. Uneven dental pads

When the paper is held in the mouth, if the tooth pad is uneven, the edge of the paper will form a wavy shape, and the mouth part will be partially wrinkled.

Second, the paper itself

1, paper thread direction

When the paper enters the machine impression, if it is straight thread, it will easily cause the silk head to wrinkle.

2, the impact of ambient temperature and humidity

The change of ambient temperature and humidity causes the uneven water content of the paper, such as the surrounding water content is greater than the middle, resulting in flanged edges, and the paper is easy to wrinkle when printing.

3. The paper marks are too deep

Because the tapping force is improper, the tapping marks are too deep and too dense, and it is easy to produce wrinkles at the crease of the tapping paper when printing.

4, the paper water content is too much

The paper has too much water content, and the fiber of the paper itself expands. In the process of imprinting, the expanded fiber becomes narrow from hypertrophy, and it is easy to produce a dendritic fold that reaches to the direction of the trailing tip.

Third, wrinkle solution

1, adjust the drum teeth, so that its holding force is average, so that the printing sheet is in the proper position of the teeth, and eliminate the wrinkling fault caused by the paper handover imbalance.

2. When embossing, ensure that the paper is flat and close to the embossing cylinder.

3, the printing sheet is properly knocked to improve the printability of the paper, so as to eliminate the purpose of the next color printing wrinkle.

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