In the printing process, paper bow wrinkles (pills) is one of the most common failures, and the economic losses are relatively large. There are two main reasons for this type of failure: First, the paper itself (mostly appearing in non-paint Paper) and secondly, improper adjustment of the machine, and the following analysis of its causes and treatment methods according to its shape.
1, small hair pleats
The reason for this kind of pleats:
(1) The "foliage" produced after the paper absorbs moisture (the paper itself has uneven moisture content or the relative humidity of the shop is high, and the paper has a low moisture content).
(2) The ink on the back of the two-side printing is “stacked†(the ink on the surface of the impression cylinder is too thick, causing local pressure to change).
Approach:
Hang the paper again; if it is printed on both sides, be sure to wash the impression cylinder.
2. Straight, straight pleats (with folds in the middle of the paper)
The main reason for this kind of pleats is the deformation of the paper (tight edges).
Approach:
Re-hanging the paper, if some printing plants do not have equipment for hanging paper, you can dip the printed unprinted printing paper one week in advance, place it in the printing room to adapt to the temperature and humidity around the machine, and then cut it when printing. on board.
3, large pleats
The reason for this kind of pleats:
(1) The large paper corners are curled up and the grippers are not good.
(2) Paper grippers on one side of the paper are too light.
(3) The paper angle floats
(4) The side specified position is not proper, and the paper corner touches the paper notch.
Approach:
After the paper is knocked and processed, it is printed on the machine; for the looser gripper, the paper needs to be readjusted.
[Case]:
A factory J2105 machine printing middle school textbooks, color inserts. Using 128g/copperplate printing paper, shortly after the official opening, it was found that occasional external pleats occurred, after careful observation by using the outside prescribed position, concluded that the paper pulls the paper in the side guide pull, the paper angle and the feed table The gaps collide, causing pleats to appear.
Approach:
The lateral rules are properly displaced to avoid the gap.
[Expert Tips]:
Similar to this kind of phenomenon, the captain should deal with it in advance and cannot wait until the problem arises.
4, arc-shaped pleats
The main reason for this kind of pleats is: the middle part of the gripper is too loose, causing the phenomenon of paper jamming, and the pleats are pulled out during printing.
Approach:
Calibrate the force of the gripper. If the pad is too smooth, replace it with a new one.
[Case]:
A factory used a four-color offset press to print a corporate advertising brochure, and found arc-shaped folds in places where portraits were printed in the latter half (not every one).
[case analysis]:
According to the conventional treatment method, the force of the paper teeth is checked, but in this case, the gripper has a good grip strength. Later, the black density of the part where the folds are found is high, especially the red ink density is too high, resulting in this. The peeling force is increased, and the gripper is slightly unsuitable and the above failure will occur.
Approach:
Re-plate, put the portrait of the person in the mouth or the front half of the paper, the fault disappears.
[Expert Tips]:
The portrait of a person or a product with strict fit requirements, such as a portrait of a person or a smaller picture, is usually best placed in the front half of a mouthwash or printed paper. In addition, if the density of ink is high, it should not be printed in the latter half.
5, large scattered hair pleats
The reason for this kind of pleats:
(1) The impression cylinder grippers have two or more loose at one place, and they cannot even hold the paper.
(2) The tooth gaps of the paper-feeding teeth are uneven, which causes the paper edge of the paper to become a wavy curve, and the length of the paper is shortened when the printing cylinder grips the paper and presses against the paper. Pleat.
Treatment method: Check the impression cylinder gripper force.
1, small hair pleats
The reason for this kind of pleats:
(1) The "foliage" produced after the paper absorbs moisture (the paper itself has uneven moisture content or the relative humidity of the shop is high, and the paper has a low moisture content).
(2) The ink on the back of the two-side printing is “stacked†(the ink on the surface of the impression cylinder is too thick, causing local pressure to change).
Approach:
Hang the paper again; if it is printed on both sides, be sure to wash the impression cylinder.
2. Straight, straight pleats (with folds in the middle of the paper)
The main reason for this kind of pleats is the deformation of the paper (tight edges).
Approach:
Re-hanging the paper, if some printing plants do not have equipment for hanging paper, you can dip the printed unprinted printing paper one week in advance, place it in the printing room to adapt to the temperature and humidity around the machine, and then cut it when printing. on board.
3, large pleats
The reason for this kind of pleats:
(1) The large paper corners are curled up and the grippers are not good.
(2) Paper grippers on one side of the paper are too light.
(3) The paper angle floats
(4) The side specified position is not proper, and the paper corner touches the paper notch.
Approach:
After the paper is knocked and processed, it is printed on the machine; for the looser gripper, the paper needs to be readjusted.
[Case]:
A factory J2105 machine printing middle school textbooks, color inserts. Using 128g/copperplate printing paper, shortly after the official opening, it was found that occasional external pleats occurred, after careful observation by using the outside prescribed position, concluded that the paper pulls the paper in the side guide pull, the paper angle and the feed table The gaps collide, causing pleats to appear.
Approach:
The lateral rules are properly displaced to avoid the gap.
[Expert Tips]:
Similar to this kind of phenomenon, the captain should deal with it in advance and cannot wait until the problem arises.
4, arc-shaped pleats
The main reason for this kind of pleats is: the middle part of the gripper is too loose, causing the phenomenon of paper jamming, and the pleats are pulled out during printing.
Approach:
Calibrate the force of the gripper. If the pad is too smooth, replace it with a new one.
[Case]:
A factory used a four-color offset press to print a corporate advertising brochure, and found arc-shaped folds in places where portraits were printed in the latter half (not every one).
[case analysis]:
According to the conventional treatment method, the force of the paper teeth is checked, but in this case, the gripper has a good grip strength. Later, the black density of the part where the folds are found is high, especially the red ink density is too high, resulting in this. The peeling force is increased, and the gripper is slightly unsuitable and the above failure will occur.
Approach:
Re-plate, put the portrait of the person in the mouth or the front half of the paper, the fault disappears.
[Expert Tips]:
The portrait of a person or a product with strict fit requirements, such as a portrait of a person or a smaller picture, is usually best placed in the front half of a mouthwash or printed paper. In addition, if the density of ink is high, it should not be printed in the latter half.
5, large scattered hair pleats
The reason for this kind of pleats:
(1) The impression cylinder grippers have two or more loose at one place, and they cannot even hold the paper.
(2) The tooth gaps of the paper-feeding teeth are uneven, which causes the paper edge of the paper to become a wavy curve, and the length of the paper is shortened when the printing cylinder grips the paper and presses against the paper. Pleat.
Treatment method: Check the impression cylinder gripper force.
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