The most popular multicolor overprint and the hygr

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Multicolor overprint and moisture absorption deformability of paper types there are many factors that affect the accuracy of overprint in multicolor printing. The paper positioning device and the paper feeding system do not operate normally, the printing plate is excessively worn, the pad is too thick or thin, the printing pressure is too large, the rubber blanket is aging and deformed, too much wetting liquid, and the accuracy of the printer is lost, etc. the permanent reuse of the input data once will have varying degrees of impact on the registration accuracy. 1. What is called the test accuracy. The influence of these factors is complex. Some can complement each other, while others may overlap each other

in addition to the above factors, the most prominent and common factor affecting the accuracy of overprint is that the elongation of some materials can be above 1000%, which is the moisture absorption change caused by the change of water content in the paper during the printing process, which is more deeply utilized in other emerging fields such as new energy, household appliances, building materials, etc

when the moisture content of the paper changes, not only the length and width of the paper change due to the expansion or contraction of the paper, but also the local size of the paper changes due to the increase or decrease of the moisture content, resulting in various deformation of the paper, such as curl, wrinkle, ripple, etc. Some of these deformations are reversible, while others are irreversible. Some deformations bring difficulties to the printing operation, while others seriously affect the quality of the printed matter. For example, when printing a map, after printing one color, if the paper is obviously elongated after absorbing the fountain solution, when printing the second color, the boundary of one country may be printed into the territory of another country, so that the printed matter has to be invalidated. For another example, when the relative humidity of the printing workshop is high, and the original water content of the paper is low, the edge will absorb water and stretch after the paper is stacked in the workshop for a period of time, resulting in the phenomenon of "Ruffle edge". On the contrary, the relative humidity of the air in the printing workshop is relatively low, and the original moisture content of the paper is relatively high. After storage, due to the rapid edge dehumidification, there will be "tight edges". When printing with such paper, due to the uneven edge of the paper, it is easy to cause inaccurate positioning of the front gauge and side gauge, so it can also cause inaccurate overprint

therefore, it is necessary to study the influence law of paper moisture absorption performance and moisture content change on dimensional stability, and formulate printing process and humidity regulation specifications according to this law. It is also necessary to explore the measures to overcome the inaccurate overprint caused by paper deformation, so as to reduce printing quality accidents and improve the printing quality level

reprinted from: Fuzhou printing

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