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First, the printing caused by pulling hair, powder failure printing operation of the paper in the ink transfer instant, under the inertia force, the ink adhesion, peeling force, the printing plate adhesive force, such as greater than the paper surface strength, the paper surface It will produce hair pulling and powder falling.
When the hair is pulled out and powder is severe, it adheres to the printing plate or the blanket. White spots are left on the graphic portion of the paper. Some of the fiber hairs, fillers, etc. that are stuck can be brought into the ink by the ink roller, causing the printed product to be blurred. In addition, the paper on the printing plate is reversed and mixed with the ink on the ink roller and the ink fountain. As the printing progresses, more and more paper hairs and paper powders accumulate on the printing plate, which seriously affects the full transfer of the printing ink. Causes shutdown scrubbing, reducing production efficiency. In order for the printing press to operate normally, the paper must reach a certain strength. The equation is the face of the steam where a paper is produced in a paper surface strength steam-peel tension where an ink on the paper surface adhesion force of a plate or blanket adsorption force during the printing process, the paper is a straight month of constant. In order to prevent the occurrence of pull-up and powder-flooding in printing, in the case of printing process operation and printing quality, it is possible to adjust each soul to adapt and balance the lunar straightness. Peel tension Peel tension is the force between the ink, blanket, and paper. Under the precondition that other conditions remain unchanged, the limit value of printing speed can be obtained through calculation, which can avoid or reduce the phenomena of paper pulling and powder falling off.
4 Adhesion of the ink to the paper surface The adhesion of the ink to the paper is mainly caused by the separation of the ink at the surface of the paper.
The ink can be reduced in the degree of ink and the thickness of the ink layer can be reduced to reduce the adhesion of the ink to the paper surface. 8 The adhesion of printing plates or rubber blankets does not need to consider the value of 8 under normal conditions. The main reason is that the rubber blanket wears out and ages, resulting in hair-jamming, resulting in pull-up and powder-failure. At this time, it is necessary to frequently scrub the blanket or replace it with a new blanket. 4 Paper-cutting Operation Paper-like paper scraps, which are similar to the faulty hair-pulling, are mainly produced by the cutter when cutting the paper.
For example, the blade of the paper cutting machine wears and is not fast, and the upper and lower blades (introduced by the stainless steel blade) do not coincide with each other. When the paper is cut, small movements cause fine fiber scraps and the like to be detached from the paper or the edge, and paper dust can be generated.
Paper powder scraps are generally composed of a few or several tens of fibers and are commonly found on the edges of paper. At this point, the cutter must be replaced in time to avoid such problems. 8 Electrostatic problems In printing, the use of static-charged paper can cause serious problems, because paper jamming can cause automatic feed picking or double-sheeting. What is more serious is that paper powder confetti will adhere to the paper. There is a close relationship between printed paper dust and static electricity. Because only a small static voltage is generated, the fine paper powder scraps of the cutting machine during the cutting process are adsorbed on the edge of the paper, and the paper powder scraps enter the surface layer of the paper during the printing process. This produces a similar printing failure. Therefore, static elimination devices must be used to eliminate static electricity.
Second, the papermaking process caused by pulling hair, powder out of trouble caused by papermaking technology to pull the hair out of the powder due to the following fiber ratio and beating operation is not proper, the slurry contains a large number of finely divided fibers and heterocytic cells, beaten too low, poor fiber binding, Easy to fall off. 4 too much filler added in the paper is not strong, easy to fall off. (8) The fiber of the papermaking department is not well bonded, the pressing pressure is not enough, the dryer temperature is not well controlled, and the surface of the paper sheet is loose and fluffy.
Paper is electrostatically generated during papermaking. Since the content of dielectrics such as alum and sodium chloride is small, the content of sizing material is too much, and the content of some fillers such as kaolin is low, the paper will be affected by high temperature and pressure in the process of drying and calendering. , make paper with high voltage static electricity. Therefore, the paper hair stays on the surface of the paper and a similar phenomenon of pulling hair occurs during the printing process. In order to avoid or reduce paper picking and dusting, the paper surface must have sufficient surface strength. The surface strength of paper refers to the fastness of the combination of the fibers, fillers, and compounds of the paper, and is an important technical indicator of the ability of the paper surface to resist external forces. The method to eliminate paper pull-out and powder-off is to address the causes of paper diseases, and to take effective measures to increase the surface bond strength of paper. This is a fundamental issue. There are many factors affecting the surface strength of paper. In addition to the papermaking process itself, the printing pressure and the temperature and humidity of the environment will also affect the surface strength of the paper. Under the effect of printing pressure, the binding force between the fibers of the paper is weakened or even broken, thereby reducing the surface strength of the paper. Embossing force can also cause the phenomenon of pulling and powdering. Therefore, the printing pressure is adjusted so that the embossing force between the blanket cylinder and the impression cylinder is appropriately reduced to reach the optimum state. The temperature and humidity of the printing shop and the moisture content of the paper itself will also have a certain influence on the surface strength of the paper.
When the moisture content of the paper is too large, the binding force between the paper fiber, the filler and the rubber material will be reduced, and the paper will also cause the phenomenon of fluffing and powder falling.
Secondly, the printing fountain solution must also be controlled in the range of the minimum amount, otherwise it will cause the paper to pull hair, powder off phenomenon. The paper appears to be napped and powdered off. During the printing process, the method of emptying the cloth can be used. That is, a clean water is overprinted before printing to remove the paper on the paper and then printed. In addition, some de-tacking agents are added to the ink to reduce the ink's degree of bruising and avoid the phenomenon of pulling and powder falling.
The first is caused by the printing operation process, such as the second degree of ink kerf, printing pressure, printing speed, fountain solution, etc., which is caused by the fact that the surface strength of the paper itself does not meet the requirements.