In the offset printing process, it may sometimes appear to be a common phenomenon, that is, the pressure on the blanket cylinder is already very high, but on the blanket, the local imprint still appears to be very empty. If a blanket lining is added to increase the printing pressure, this situation still exists. Most of this phenomenon is reflected by printed matter after replacing thicker paper with thinner paper. Why does this happen? First, the pressure of the blanket is well known. In offset printing, the blanket acts as an intermediate for the transfer of the imprint, accepts the ink from the printing plate, and transfers the ink to the paper. To ensure the good quality of the printed product, the ink layer can complete the transfer process completely. In addition to the good printing adaptability of the blanket itself, the selection of appropriate pressure is an essential technological measure. Obviously, there are two different pressure relationships between the blanket cylinder and two different objects, the plate cylinder and the impression cylinder. As long as the pressure between any of the rollers and the blanket cylinder is insufficient, the ink layer will be frustrated during the transfer process so that an intermediate fracture state cannot be formed, so that the imprint cannot be completely transferred to the paper. This is self-evident. of. On the contrary, simply increase the pressure between the two, which can produce corresponding results. In the two different pressure relationships of the blanket cylinder, a particularly important condition is often not easy to attract people's attention. This is the phenomenon that when the pressure between the blanket cylinder and the impression cylinder is too heavy, the imprint will appear empty. . At this time, the ink layer on the surface of the blanket is observed, and this emptiness phenomenon has also been shown.
This phenomenon is generally prone to occur in the following contexts: a. Improperly adjusting the center distance between the blanket cylinder and the impression cylinder or calculating the thickness of the blanket lining material inside the blanket causes excessive pressure. b. When printing from thinner paper grades to thicker paper grades, there is no corresponding reduction in the pressure between the blanket cylinder and the impression cylinder. Second, the cause of imprint emptiness We know that the blanket in the imprinting process, has an unparalleled high elastic energy, that is, in the compressed state can form a compressive deformation, the pressure is removed, the blanket can quickly return to the original Stateful. This cycle of physical phenomena is the basic condition for normal printing. However, this performance of blankets is not fixed, if the excessive pressure, the blanket's high elasticity will be hurt. This is what we usually refer to as the blanket (including the inner liner of the blanket) is "crushed" phenomenon. The phenomenon of "pressure collapse" will first be reflected in the part of the blanket, and irregular expansion and changes will follow. When this happens, the ridiculously weird phenomenon mentioned at the beginning of this article is that the blanket receives heavy pressure on the one hand and the surface of the blanket is very emptied on the other. This is because when the blanket and its backing are pressed under excessive pressure, they cannot quickly or fail to return to their desired elastic height, so that the pressure between the blanket cylinder and the plate cylinder is insufficient or the local pressure is insufficient. As a result, the ink layer on the printing plate cannot be completely transferred to the blanket and the imprinting phenomenon appears. three. Judgment and identification need not be rumoured. The situation in printing is complicated and complex. We cannot simply break it, but as long as we pay attention to and carefully analyze the corresponding changes in the surrounding conditions of this issue, the pressure of the blanket cylinder and the impression cylinder is too heavy. The resulting emptiness of imprinting is also rule-based. 1. If the printed material is overstressed, the pressure on the printed material is vacant, indicating that the pressure of the two has reached a certain level. Check the padding inside the blanket: a. Paper liners are often accompanied by crushed or lining paper displacement after the wavy. b. The lining felt wool will show signs of being weighed by the weight, elasticity, and color. These all show the corresponding changes in printed material under stress. 2. In the printing state, due to excessive pressure, in the printing process, when the printing surface of the blanket cylinder and the impression cylinder are in contact with each other, special noise may occur due to excessive pressure. 3. In the case of printing process, when there are imprinting emptiness phenomenon, if people mistakenly believe that the blanket lining is not enough and blindly increase the blanket lining thickness, it will result in increasingly fierce and serious consequences. Occasionally, partial screen imprints may appear empty, and the other part may appear to be worn by the printing plate dots. These bad appearances should be the typical characteristics of the overpressure of the blanket cylinder and the impression cylinder and should be avoided as much as possible. The correct approach should be: a. Recalculate and reduce the pressure between blanket cylinder and impression cylinder. b. The crushed rubber blankets and felts were treated appropriately to improve their elastic properties and replaced with new liners. Through this operation, the ills of imprinting emptiness can be changed. Admittedly, there is also a pressure relationship between the blanket cylinder and the plate cylinder. However, if the pressure between the two is too heavy, then the imprint emptiness problem described in this paper cannot occur and only the imprint blurring phenomenon will occur. This is another situation, and it deserves to be said. Yan Jiayuan
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