Effect of friction coefficient in gravure printing

The friction in the gravure printing process mainly includes the friction of the equipment itself and the friction between the equipment and the printing material and the ink. The friction between the equipment and the printing material (film) in the printing process is the main factor, and it is often the driving force. It is resistance, so its size control plays a very important role in printing quality and printing speed in the appropriate range.

1. Selection of the coefficient of friction in printing The thin film roll for automatic printing generally requires a smaller inner layer friction coefficient and a suitable outer layer friction coefficient. The outer layer has a large friction coefficient, which may cause excessive resistance in the printing process. The material's tensile deformation affects the printing effect. If it is too small, it may cause the sliding mechanism to slip, resulting in inaccurate correction system, reduced printing fastness, and also affect the packaging speed. In addition, the fineness of the ink is low, the pigment particles are coarse, the friction coefficient during the printing process is large, and the imprint resistance rate of the printing plate is low, and the situation of pasting, ink accumulation, and ink transfer and ink inequality are easily generated during printing. Therefore, the film surface should have suitable smoothness to ensure that it can perform high-speed printing smoothly. At room temperature, the dynamic friction coefficient of the film surface is generally required to be between 0.2-0.4.

2, the impact of high temperature conditions on the friction coefficient When considering the friction coefficient, should pay particular attention to improve the ink and the substrate fastness and improve the printing speed, generally have to improve the printing environment temperature, equipment, metal parts are mostly Operating at high temperatures above 50°C. However, the increase of temperature has a great influence on the friction coefficient, because the heat transfer ability of the polymer macromolecules under high temperature conditions is strengthened, the activity speed is increased, the molecular gap becomes larger, and the change of the surface performance changes the friction coefficient of the film. In addition, the smoothness of the film is mainly achieved by adding a slip agent. After the film is formed, the slip agent migrates from the film to the surface and accumulates into a uniform thin layer, which can significantly reduce the coefficient of friction of the film. The film has a good smoothness effect. Most of these auxiliaries are inorganic polymer materials (such as amines or waxes), and have poor compatibility with the resin, usually starting from 30°C. Commonly used lubricants have become close to their melting point and become bonded. The friction of the film The coefficient rises sharply and the force exerted during the test fluctuates greatly, presenting an intermittent sliding or bonding effect. If the content of the slip agent is too high, it also affects the printability of the film, which is extremely unfavorable for printing. In general, with the increase of the ambient temperature, the friction coefficient of the material surface will have a certain change, but the size of the change will vary greatly depending on the sensitivity of the material to the temperature and the types and amounts of the additives added.

3, the determination of the friction coefficient With the rapid development of gravure printing technology, printing speed is getting higher and higher, in order to avoid waste due to the friction coefficient of the printing process to increase production efficiency, printing manufacturers must choose the appropriate coefficient of friction film, This requires manufacturers to have suitable thin-film detection equipment. Before printing, it is not only necessary to measure the coefficient of friction of the film material at room temperature, but also the friction coefficient at the actual use environment temperature. Generally according to GB 10006 (plastic film and sheet friction coefficient measurement method) and ASTM D1894 to determine the positive and negative film surface dynamic and static friction coefficient. At present, Jinan Languang Electromechanical Technology Co., Ltd., a manufacturer specializing in the production of packaging inspection equipment, has introduced a FPT-F1 friction coefficient/peel tester specifically designed to measure the dynamic and static friction coefficients of materials at very low temperatures, which can simulate room temperature -99.9. The °C test environment is closer to the actual coefficient of friction in the printing process. Moreover, the accuracy of the test can reach 0.5-level accuracy, which can take into account both domestic and foreign standards. It is very suitable for printing companies to choose suitable printing materials.

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