The printability of a printing plate refers to the maximum printing quantity that a printing plate can print within the specified printing quality range. Offset printing is based on the principle that oil and water are difficult to dissolve. The graphic and blank parts are almost printed on the same plate. In fact, the printability of a printing plate depends on the stability of the balance between oil and water between the graphic part and the blank part. No matter what the reason is, as long as the stability of any part of the plate is destroyed, the service life of the plate may be reduced, that is, the printing resistance of the plate will be reduced. The printing plate endurance is directly related to the economic benefits of offset printing production, and it is also an important condition to reduce production costs, improve output and ensure printing quality. The low printing resistance of printing plate not only brings trouble to offset printing operation, but also directly affects the quality of printing products. The printing process involves a lot of complex physical and chemical phenomena, the influence of various environmental factors and the technical quality of the operators, which will change the balance of hydrophilic and lipophilic between the graphic part and the blank part of the printing plate to a certain extent, resulting in the reduction of printing plate resistance. There are many factors that determine the printing plate resistance. This paper analyzes them from several aspects and discusses them with colleagues. 1. The quality of the printing plate itself. At present, there are many kinds of plates on the market, and the quality is also uneven. In order to meet different printing quality requirements, different kinds of plates should be carefully selected during purchasing. In the selection, attention should be paid to the composition of the plate base, whether the thickness of the photosensitive resin film is consistent, whether the plate grit is too thick or too sharp, and so on. The selection of high-quality plate material is the prerequisite for improving the printing plate resistance. At the same time, attention should be paid to the storage of the plate. If the plate is not properly preserved, it will be exposed to light, or stored for a long time and affected by moisture, resulting in oxidation of the plate Causes the smoothness to drop, even if the best plate material can not guarantee the high printing plate. 2. Technical problems in plate making process: the field density of the film used for plate printing should be above 3.8, the exposure should not be excessive, the developer should be stirred evenly, the water level should be appropriate, the temperature should be kept appropriate, attention should be paid not to over develop, the developer should keep balance, and the blade speed should be uniform. The layout should be finished thoroughly. When you wipe the paste after revision, you should wash it with a lot of water and wipe the non graphic part at the same time, which can not cause the local resin film thinning of the plate. The temperature of baking plate should not be too high or too high. Only in strict accordance with the technical requirements of plate making process can the printing plate maintain high printing resistance. [next] 3. Problems caused by improper adjustment of plate loading. During plate loading, it should be confirmed that there is no foreign matter on the back of the plate. The plate pad should be kept with proper thickness. The pressure between the plate and the water roller, blanket and ink roller should be adjusted to avoid too much pressure. In the process of debugging, in the case of printing plate without ink, the machine should not idle for too long when the water roller relies on the plate. When using wetting powder to wipe the dirt on the printing plate, the force on the graphic part should not be too large to avoid damaging the resin film on the plate. Do not continue to use the aged water roller sleeve or rubber blanket, but replace it in time. If the blanket on both sides and tail of the ink dirt is too much, should be scrubbed clean, after each version should be carefully scrubbed blanket. The water roller should also be cleaned with cleaning agent or gasoline frequently. After washing, the water roller sleeve should not leave any cleaning agent or residual gasoline. The hardened ink scale on the water roll by the plate should be carefully scraped off. It is not suitable to use the gasket with too much hardness. The uneven liner should be flattened or replaced to avoid serious wear of the printing plate. If the rubber cloth is too loose, it should be tightened, especially the new rubber blanket and gasket, which will appear relaxation after using for a period of time, and should be tightened in time. At the same time, attention should be paid to the tightness of both ends of the blanket to avoid one end too loose and one end too tight. 4. Problems caused by machine wear plate wear is the main cause of the reduction of printing resistance, it is a complex process composed of many factors, and due to the role of lipophilic and hydrophilic, different parts of the plate will be worn to varying degrees. At present, offset printing still has the effect of pressure, and with pressure, friction will inevitably occur. Friction causes the loss of the balance between oil affinity and hydrophilicity due to the abrasion of the graphic and blank parts on the plate, which is the main factor for the reduction of printing plate resistance.When the shaft sleeve of the printing machine is seriously worn, the displacement will increase, and the impact force of water roller, ink roller and blanket roller on the printing plate will increase, which will directly lead to the reduction of printing plate resistance. In this case, the corresponding accessories should be replaced or repaired properly. If it is not too serious, rubber cleaning reducing agent can be used for cleaning. At the same time, the printing speed should not be too high. [next] 5. Problems with paper, ink and bucket liquid. If the paper powder is too much, contains sand or sand particles, and the pH value is too high or too low, it will affect the blanket and printing plate. When the paper is seriously de powdered and hairy, the blanket should be often scrubbed to prevent sand particles from wearing the plate. When printing, the pH value of the water bucket should be kept at 5-6, and the water bucket should be cleaned frequently to avoid the corrosion and deterioration of the bucket liquid, which will cause the printing plate to be dirty due to corrosion, which will seriously affect the printing plate's printing resistance. Ink should be based on different varieties and different printing quality requirements, reasonable selection of inking oil, diluent, dry oil, etc. for appropriate adjustment, to avoid too high ink viscosity and reduce the printing plate resistance. As the ink itself has a certain protective effect on the resin film of the printing plate, attention should be paid to the amount of ink used in printing, otherwise it is easier to wear the plate and reduce the printing resistance. Through the above analysis, we can take some measures from the printing process to improve the printing plate resistance: 1) under the premise of ensuring the printing quality, keep the minimum pressure between the rollers and reduce the friction of the plate. ② As far as possible to ensure that the surface linear speed of each roller and ink roller is equal to reduce the plate wear caused by slip. ③ Under the principle of printing plate not dirty, use the least water, and maintain normal water supply to prevent large ink. ④ The pH value of the bucket liquid should be controlled correctly and kept in an appropriate range, and the change should not be too large. ⑤ Maintain the normal ink supply, prevent the big and small. ⑥ Control the thickness of ink layer to prevent imprinting spreading. ⑦ Strictly control the emulsification value of the ink, and timely remove the ink roller deinking caused by emulsification. ⑧ The drying agent should be used reasonably to prevent the early drying of each printing surface. ⑨ When the machine stops, wipe the glue in time to prevent the printing plate from oxidation and dirty. ⑩ All kinds of man-made damage should be avoided in technology.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
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