1. What is inverted hair
When printing solids, lines, or text, burrs will occur at the edges of the graphics. This is often referred to as Shun Mao. The burrs in the direction of the bite are called inverted hairs, and the burrs in the direction of the trailing hair are called smooth hairs. It has the same direction on the printing plate, blanket and printed product, otherwise it may be a squeeze phenomenon or a ghost phenomenon.
2. Influencing factors
When the following three factors exist at the same time, the inverted hair will be produced:
1. The lining of the plate cylinder and the rubber cylinder is incorrect, so that the radius of the plate cylinder and the radius of the rubber cylinder are not equal, and the difference is large.
2. There is more paper, powder, sand, etc. on the surface of the paper, falling off on the blanket.
3. The metal matrix of the printing plate is not hard enough.
The above three factors are not related to the impression cylinder.
3. Failure analysis and solution
1. Inverted hair: under the condition of the above three factors, when the linear velocity of the surface of R printing> R oak 'plate is higher than the linear velocity of the surface of the blanket, the two will produce sliding friction during the combined pressure. The friction between the two causes the ink on the printing plate and the blanket to squeeze in opposite directions. Because R India> R Oak 'is fast, the ink on its surface is elongated toward the trailing direction; while the linear velocity on the surface of the blanket is slow, the ink on its surface is elongated toward the mouth.
The elongated ink marks on the printing plate are removed due to the grease-removing effect of the water roller and the water bucket liquid and the ink-receiving effect of the ink roller. Although the elongated ink was continuously produced, it was continuously removed. Therefore, the elongation of ink on the printing plate is instantaneous, so it does not become a source of backwards. The stretched ink on the blanket cannot be transferred to the paper. Due to the sticky force of the ink blot, there are more paper fallouts accumulating at the blotting area than elsewhere. These exfoliated substances are mixed with ink marks to become oily deposits. When the printing plate and the rubber blanket are pressed to produce sliding friction, it slides and accumulates on the blanket in the direction of the force generated by the printing plate. As the oily deposits on the blanket continue to increase and thicken in the direction of the imprint, the printing plate sand that contacts the area is worn and damaged. It is also eroded by oil, gradually lipophilic and oleophilic, and finally produces burrs, and the burrs will become longer and longer. This is the reason why the burrs on the printing plate shine when the inverted hair occurs.
Treatment method: reduce the plate liner, increase the number of liners drawn in the blanket, and increase the center distance between the rubber cylinder and the impression cylinder appropriately. If the number of pads of the blanket meets the standard data, the center distance between the plate cylinder and the blanket cylinder should be reduced after the plate is removed.
2. Smooth hair: When Rprint> R rubber, smooth hair is produced under the three factors that produce inverted smooth hair. The direction of its imprint is opposite to that of inverted hair, and the principle of generation is the same as that of inverted hair.
Treatment method: reduce the liner in the blanket. If the plate liner is lower than the standard data, increase the liner in the plate, and at the same time, reduce the center distance between the impression cylinder and the rubber cylinder. If the thickness of the printing plate liner conforms to the standard data, the center distance between the three cylinders needs to be reduced at the same time.
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