硌版
Sometimes the paper sheet will have fiber clusters gathered from the surface of the paper or non-digested blocks such as small blocks and knots. The former is called pulp block and the latter is called hard block. Some people also call the two together. When a pad or other hard block appears on the surface of the paper during printing, a stencil failure occurs.
The effect of pulp blocks and other rigid blocks on the use of paper is severe, especially for offset printing. Accidental, smaller flaws can make the layout worse, and if there are repeated flaws in the paper, it will inevitably damage the printing plate; individual large flaws will smash or break the blanket, causing serious printing accidents. Even with letterpress printing, larger, harder files can ruin the layout and make it impossible to capture ink.
In the printing process, since paper feeding, printing, and paper discharge are continuously performed at high speed, once the layout is damaged, even if it is discovered in time, many papers are lost, and if it is found that the loss is greater. In addition, loss caused by loss of plate material and change of plate version, such superimposed loss is more serious. When such problems occur, it is necessary to negotiate the damages caused by the paper mills.
Printed
In the calendering section of a paper machine, the occurrence of paper breakage due to the occurrence of broken paper is common. These pieces of shreds should be removed during rewinding and slitting. If there are scraps of paper caught in the paper, it will cause missing prints and malfunctions during printing. Caused by the fact that the factory often does not attach much importance to the problem of one or two pieces of paper scraps in the paper, thinking that there is no major impact. In fact, the shredded paper will bring great troubles to the printing and a greater economic loss.
When printing on web or flatbed paper, if there are scraps of paper in it, these scraps of paper will adhere to the surface of the paper and enter the printer. The printing pressure and the viscosity of the ink will cause the shreds of paper to adhere to the blanket cylinder. Or layout. In this way, the text and images on the printing plate cannot be transferred to the paper, so that the printed matter forms missing printing (commonly known as window opening). On high-speed printers, once this occurs, dozens or even hundreds of prints can be made waste, and the removal of the shreds from the squeegee or the plate needs to be stopped. Therefore, the missed print caused by scrap paper must be taken seriously.
Imprinting cylinders and prints are contaminated
This contamination is often caused by holes and folds in the paper.
Holes are small holes that can be seen through the paper with the naked eye under light. Big hole called hole.
Paper with holes may cause problems with the quality of missing pens during printing. When there is a large hole or hole in the paper, the ink on the printing plate or blanket cylinder is transferred from the hole to the impression cylinder, so that the printing roller continuously transfers the ink to the other side of the printed product while continuing to rotate. Damage to prints. When the ink is transferred to the impression cylinder, if the viscosity of the ink is high, the paper will also be stuck on both sides and be torn off. The torn paper sticks to the blanket cylinder or plate, and the printing failure caused by the scrap paper mentioned above also occurs.
The folding angle refers to a corner of the printing paper coming back. The folding angle also causes serious printing failure.
When printed with folded corners, the printed matter on the sheet is not printed on one sheet, and one sheet is printed on the back. In addition, the ink is also transferred to the impression cylinder at the corner portions, causing the impression cylinder to continuously contaminate the back side of the print, resulting in a lot of scrap. What's more, if the paper is thicker and stiffer, the corners may also damage the blanket, which will cause the machine to stop changing, which will cause similar failures like block and hard block.
Source: Paper Easy
