In printing operations, especially printing full-page solids or solid borders and other printed matter, ink stains are most likely to occur. Ink stains are usually ink skins and other objects stuck on the surface of the printing plate, which may be ink skins, or may be dirt from rubber rollers or paper and paper fur. The summary and analysis are as follows:
1. The ink skin in the ink. This situation is caused by new ink in the old ink tank, or the crust on the surface or edge of the new ink may not be cleaned. During the printing process, it will be adsorbed on the printing plate and text, and transferred to the The black spots in the middle and white circles around the printed matter appear on the printed product, as shown in the figure. Corresponding measures can be taken from the following aspects: â‘ first roll the ink once, if it still cannot be solved, you should consider replacing the new ink; â‘¡ if there is only a small amount of ink in the ink, if there are not many printed sheets and the requirements are not very strict , You can use the method of closing the small ink head screws and putting more teeth to keep the ink pickup stuck in the ink fountain. This method has a certain effect, but for more printed sheets, it will accumulate less and affect the printing quality; â‘¢When storing the ink, the old ink tank should be cleaned and put in again, and then the kraft paper used for packaging is cut into a paper cover that matches the size of the opening of the ink tank, and the oil cover is coated on it to make it flat. This method It has a certain effect on preserving old ink and preventing ink skin.
2. Falling off of rubber roller. In the long-term use of the rubber roller, due to various reasons such as cleaning, acid water, ink oiliness, etc., the surface of the rubber roller is uneven, the oxide film or the surface is aging and smooth, and the rubber layer of the rubber roller has numerous cracks. In the printing process, these cracks will have irregular black hard blocks falling down and sticking to the printing plate, transferred to the printed product through the blanket, and the shape of the ink stain as shown in the figure will appear. It is necessary to master the correct use method and maintenance of the rubber roller to maintain the surface performance, geometry and dimensional accuracy of the rubber roller with good working performance and stability, and prevent the premature failure of the rubber roller performance due to non-filling and poor maintenance. When installing and adjusting, it must ensure its proper technical accuracy, should be handled with care, and should not collide with the roll neck and roll surface adhesive layer and cause roll body loss, bending or adhesive layer damage. When adjusting the contact pressure between the rubber roller and the rubber roller, and between the rubber roller and the printing plate, it should be adjusted and determined according to the elasticity and hardness of the rubber roller and its role in the system, so that it is always maintained during the operation. Good contact state, balanced force and uniformity. At the same time, it is necessary to grasp the necessary links such as the maintenance and maintenance of the rubber roller. Before and after the rubber roller is used, the roller surface must be thoroughly cleaned with a cleaning agent to keep the roller surface free of dirt and restore its ideal working state on the surface. In the course of use, the rubber roller should be prevented from contacting with strong acids, alkalis or organic solvents. During the holidays, the rubber roller should be taken out and stored in a ventilated, dry, cool place. It is strictly prohibited to overlap, squeeze, and glue layer Adhesion and deformation under compression. It can be seen that strengthening the use, storage and maintenance of the rubber roller is the main method to prevent the rubber roller from falling off:
3. Paper dirt. In the papermaking process, due to the relationship between papermaking raw materials and technical aspects, the sludge in the paper, such as paper wool, pulp, etc., during the printing process, these sludge may accumulate on the blanket The surface affects the normal transmission of the dots, and may also be transferred from the surface of the blanket to the printing plate and appear on the printed product, becoming a white circle with burr-shaped ink stains around it (as shown). Whether the paper dirt accumulates on the printing plate or the blanket, it seriously affects the quality of the printed matter. Originally, paper wool can absorb water and oil. When paper wool is adsorbed on the printing plate and text, as the printing drum rotates, the paper wool is moistened by the bucket fluid and pressurized by the water roller, and is closely attached to the printing. On the layout text, the inking roller is then inked. At this time, the wet paper wool has oil resistance. Although the ink is not absorbed by the four inking rollers, ink stains will appear when transferred to the blanket for imprinting. phenomenon. For this phenomenon, we must first reduce the water content of the plate and reduce the pressure between the water roller and the surface of the plate, so as to minimize the wetting of the paper wool on the surface of the printing plate, and reduce the oil resistance of the paper wool to increase its inking power and make it not stick. On the plate; secondly, increase the viscosity and fluidity of the ink, and increase the pressure on the surface of the first three inking rollers, so that the paper wool remaining on the plate is inked by the inking roller, and the paper wool is pulled out and transferred to the ink roller. Then gather them on the small iron roller, and wipe them clean when the machine stops to load paper. Of course, in order to ensure the quality of the printed products, the paper attached to the paper with more serious paper wool can be replaced by white paper or overprinted with white oil or water-washed adhesive tape.
All in all, the occurrence of ink stains in printed matter is not only due to material factors, but also many factors such as process, technology, equipment, etc. It is necessary to strengthen supervision and monitoring in all aspects before, during and after printing. .
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