The quality of printed products is inextricably linked to the nature of the paper. Therefore, in the printing operation, the paper requirements will vary with the nature of the printed matter and the quality requirements. Different papers have different adaptability to various printing processes due to their different physical and chemical properties.

Paper ink absorption

In the printing process, the transfer of ink is completed by the capillary action composed of pressure and the interweaving gap of paper fibers. When the paper is subjected to printing pressure, the interwoven fiber gap is compressed; when the pressure disappears, the surface of the paper recovers to its original state due to the elasticity and absorbs ink at the same time, which is a simple process of forming a print.

The ink absorption of paper is the performance of fiber properties, reflecting the interweaving conditions between fibers, the nature and content of fillers and gums, etc. Its essence is the capillary adsorption of pores between fibers to the ink binder. The absorption of ink by paper is related to the pressure of the printing machine, the length of the printing time, the viscosity of the ink and the structure of the paper itself. The author believes that paper with a lot of lignin has great ink absorption. For example, newsprint has less filler and glue, good ink absorption, and easy to adjust the pressure, which can reduce the pressure appropriately, which can increase the printing durability of the printing plate. However, if the paper is too slack and the fiber gap is too large, a "brushing" phenomenon will occur when the ink viscosity is large; if the ink viscosity is low, the linking material will quickly penetrate into the paper fibers, resulting in a "pass-through" phenomenon. Therefore, it is necessary to properly adjust the viscosity of the ink to prevent the ink on the surface from falling off after the penetration of the binder in the ink, which will cause the product to lose its gloss and affect the printing quality.

Paper smoothness

The smoothness of the paper is an important indicator, and it is a comprehensive characteristic of the paper surface being uniform, smooth and smooth. Some papers have rough surfaces and poor smoothness. Not only the front and back sides are inconsistent, but also the same side or even the same side of a piece of paper, which affects the consistency of the ink color on the layout. The smoothness of the paper has a great influence on the printing, and is related to the reproduction of the dots and whether the dots are expanded. For the same kind of paper, the paper with good smoothness requires less printing pressure; the paper with poor smoothness needs to increase the printing pressure in order to meet the requirements of pen strokes, graphics, and dots. Therefore, for papers with poor smoothness, the ink color is difficult to grasp, and increased pressure will affect the printing durability of the printing plate.

The products printed on the paper with smoother surface are clear and eye-catching. This is because the paper with high smoothness can be in good contact with the printing plate during imprinting, so that the ink layer on the printing plate is evenly transferred to the paper surface. Conversely, the paper with poor smoothness is uneven and uneven. Under other conditions unchanged (printing pressure and ink), the contact between the paper surface and the printing plate surface is uneven during imprinting, which affects the transfer of the ink layer. [next]

Paper elasticity and plasticity

The elasticity of the paper refers to the degree to which the paper can recover after the printing pressure disappears. The plasticity of the paper refers to the degree of deformation caused by the printing pressure. The elasticity of the paper affects the ink absorption performance; the paper has good plasticity, which can ensure that the printing plate is better in contact with the paper and obtain a full ink color imprint. Therefore, the elasticity of the paper directly affects the printing pressure and the amount of ink supply. Different papers have different elasticity and plasticity. Depending on the nature of the paper, different operations should be applied. The printing pressure of paper with higher elasticity should be higher, and the ink supply can be smaller; on the contrary, the printing pressure of paper with lower elasticity should be lower, and the ink supply can be increased. In the process of operation, the principle of not excessively increasing the pressure should be adopted on the premise of not affecting the quality, so as to improve the durability of the printing plate.

Paper cutting

The cutting of paper is the first important link in the printing process, which has a certain impact on the quality of semi-finished products and processed printing. Therefore, improving the quality of paper cutting is one of the important issues of printing technology.

The paper cutter has mechanical, hydraulic, computer program control and other types. The old model imported computer paper cutter system is outdated and has many failures, which causes great inconvenience to cutting. Ordinary paper cutters have poor accuracy, low efficiency, and high scrap rate, which greatly affects product quality. Nowadays, the modified or new type of paper cutting machine (SWD) adopts a whole series of technologies of computer, digital display and projection screen. It has good safety performance, convenient operation and high precision, which is a good way to solve the problem.

The four corners of the paper cut by the paper cutter should be at right angles; the size of each stack of paper is consistent up and down, not skewed or skewed, and the straightness is high, and the error of the paper cutting is preferably not more than 0.1mm; the cut should be clean and tidy to avoid appearance Cracks, slivers, roads, fluff, etc .; the lower layer of paper should be cut to the home, not dirty or broken. In addition, there are specific requirements and prescribed errors in the cutting of paper and forest materials for different purposes.

Pay attention to the following items when operating the paper cutter: Check the machine, motor, knife edge, switch, brake and other parts during work and work, especially pay attention to whether there is oil stain under the pressure bar, whether there is moisture on the paper table, there is rust, whether there is nail head, etc. . Before cutting the paper, you should carefully read the work sheet carefully, clarify the regulatory surface of the printed semi-finished products, and follow the regulatory size; the quantity check is accurate. Papers and finished products that are not of the same type should be stacked separately to avoid confusion. The front and back of the paper and the horizontal and vertical threads should also be stacked separately. According to the specified size, the material should not be of different sizes or skewed. The cut paper should be stacked separately, and the name of the printed piece or the number of the printed slip must be marked on the paper.

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