Factors affecting the quality of prints In addition to processes and materials, printing speeds also play a role. Familiar with the relationship between them, is an essential operator of the press, especially in modern offset press to multicolor. Rapid development is particularly necessary today.
1. Effect of printing speed on printing pressure
To make the printing plate coated with ink graphics can be clearly transferred to the surface of the substrate. Must have enough printing pressure. However, the applied printing pressure should not be too large. Excessive printing pressure will cause the printing material to continue to deform, the prints become thicker, and the dots will be graded and pasted, which will affect the clarity of the graphic and text, and at the same time it will aggravate the wear of the printing plate. The plate's resistance to printing forces has decreased. When the printing pressure is insufficient, there is no sufficient reliable contact between the printing plate and the blanket, and the imprinting will be shallow, affecting the clarity of the graphic and text.
As the printing speed increases, the blotting ink becomes lighter. At first, it was thought that the printing speed increased and the printing pressure decreased. This was not the case. Because when the printing speed increases, the imprinting time decreases, and the pressure time on the print surface decreases, the amount of ink transferred to the surface of the substrate also decreases, and the density decreases. As a result, the blotting ink becomes lighter. In actual production, in order to compensate for this defect, a method of increasing the printing pressure is often used.
In addition, in the case of the same footprint, the printing speed is directly related to the size of the impression cylinder of the printing press. In order to obtain a print of the same print quality, the printing speed of a large press of an impression cylinder must be slower than the printing speed of a printing press of a smaller size of an impression cylinder.
2. Effect of printing speed on paper
As a substrate, paper will undergo certain deformation under pressure, mainly elastic deformation and plastic deformation. Modern multi-color high-speed printing presses, the imprinting interval between the two color groups is very short, only a few tenths of a second, in such a short time, the wet-pressed wet-overprinting ink simply can not be completely dry. In this process, the paper undergoes several times of wetting and embossing, and its surface strength will be reduced. Therefore, it is required that the water absorptivity of the printing paper cannot be too strong. Otherwise, the overprinting will not only result from the excessive water absorption of the paper. Quasi, but also very prone to paper pulling phenomenon.
Practice has proved that under certain ink viscosity conditions, the printing speed is the main factor influencing whether the paper will be pulled during the printing process. Under normal circumstances, the faster the printing speed, the more obvious the phenomenon of paper pulling.
3. Effect of printing speed on ink transfer
Fundamentally speaking, the printing process is the process of ink transfer, and the ink is mainly from the ink fountain, the ink fountain roller, the ink roller, the printing plate, the blanket, and the surface of the substrate. In this process, the effect of changes in printing speed on the ink is enormous.
The ink is output from the ink fountain and transferred by the ink fountain roller. After being squeezed, sheared, and torn between the rollers, the ink is quickly beaten. At the same time, a large amount of heat is generated. These heat increase the temperature of the ink and make it sticky. Decline and mobility. The faster the printing speed, the more heat is generated and the higher the ink temperature. If the generated heat can not be taken away in time, then the ink at an excessively high temperature reflected on the printed matter is a blur of dots, unclearness, and even the appearance of stencil, ink, etc., which seriously affects the quality of the printed matter.
4. Effect of printing speed on printing plate
In a printing cycle, the plates are successively in contact with and against the water roller, the ink roller, and the blanket cylinder. Obviously, the increase in printing speed will give a large impact on the printing plate, thereby accelerating the plate wear, resulting in local loss of the network.
In short, a good print must be equipment. Process, technology and many other aspects of the comprehensive embodiment. In actual work, it is necessary to avoid frequent acceleration and deceleration. This will not only help ensure the quality of the printed matter, but also is an important guarantee for the good operation of the equipment.
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