Lithography Technology (Chinese)

包装 Packing and printing money needs different papers. At present, there are many paper manufacturers and brands at home and abroad with different quality. Buy paper, became a very professional knowledge. At present, the issue of purchasing paper by Guangdong printing companies is often determined by the material supply department or individual based on experience and feelings, and there are considerable limitations. Since the use of paper is an extremely important part of the entire production chain, it should be prudent. There should be accumulation of information. There should be inspections when entering the factory. There should be an analysis during the use process. After use, there is a summary. The results are recorded, and the data are filed for future reference. Before entering the factory, we listened more to the views of the production line workers, not only considering their prices, but also focusing on their quality and performance. Paper procurement personnel should thoroughly master relevant paper information: domestic and foreign manufacturers, brands, and quality of production of various types of paper; the paper's time of drying, the laws of dry humidity, the law of changes in moisture absorption, water resistance, mechanical strength, and dimensional stability. Absorb ink-reducing performance, its acid-base reaction; color, whiteness, smoothness, transparency, surface sizing; difference between positive and negative sides, cross-cutting silk (grain) condition; hair loss, powder loss, moldy spots, etc. Happening. In short, we must attach great importance to the purchase of paper, we must regard it as a highly professional and highly technical work. This will not only be beneficial to accurate registration, but also very beneficial to the overall quality of the product. 
In the printing process and after printing, various measures to prevent deformation of printed sheets and semi-finished products are well-known in the printing industry. However, it is very strange that only a handful of the printing factories we visited had very strict enforcement of these measures. Most enterprises, though they have systems and facilities, cannot be effectively put into practice. A few companies do not even have the necessary facilities. For example, some very simple but extremely important measures to prevent deformation of printed sheets: “On the top surface of each stack of paper and semi-finished products, cover a stack (not less than 50 sheets) of waste paper with the same specifications, The application hand repeatedly sweeps the surface and discharges the air between the paper stacks.” “The printed semi-finished products, including single-color, double-color, and four-color semi-finished paper piles, are all covered with special large plastic bags. Paper stacks are sealed tightly from top to bottom and bundled with single-sided adhesive tape every 50 Cm from top to bottom. During operation, the air should be removed, and the air be squeezed tightly to squeeze the air out of the plastic bag to bring the air close to the air. The possibility of products is reduced to the minimum limit.” These measures, although simple, are very conducive to the registration, but due to the tediousness, they are often overlooked by some companies and operators. As long as we grasp the word "seriously", the possibility of deformation of printed sheets will be minimized. 
The paper's fiber structure and paper pattern, also known as paper silk, are also issues that require careful study and careful handling. According to the experts’ study, most papers and longitudinal paper lines, ie, silkworms, and stenciled papers, are relatively stable in size and less in deformation, while papers with horizontal paper grain and silky-streaked paper are relatively large in size and different in quality. The amount of deformation of the paper can be as large as 2 to 10 times. This is a question that cannot be taken care of. All kinds of offset presses of different sizes are suitable for the printing of paper in the vertical direction of the silk roll and its rollers, which greatly contributes to preventing the longitudinal deformation of printed sheets. 
All measures that are conducive to the prevention of paper deformation should not be taken lightly and should be repeatedly emphasized to ensure that measures are implemented. For example, the front side of the paper is smooth and dense, and the single-sided paper is covered with glue on the front side, and the reverse side is relatively rough with net marks. The degree of moisture absorption, deformation, and ink absorption that affect the color is completely different and must be strictly used. Moreover, acid paper has far better water absorption than alkaline paper and should be considered when it is selected. During storage and operation, the paper should be kept away from water sources, reservoirs, and wet floors. It should be laid flat, without staggering the edges of the paper, and it should not be folded. Always pay attention to moisture, sun protection, and heat protection. Some papers with poor quality, in monochrome, When printing with a two-color machine, humidity treatment and the like should be performed before printing. The paper ring is handled properly, and there is a basis for "accurate registration."
Fourth, in the printing process, the key to “accurate transference” lies in the fact that the transfer of printed sheets is “correct transfer of paper, precise registration of printed sheets,” and whether or not it is coordinated with the various parts of the paper transport. 
In the mechanical structure of the offset press, the paper feeding device can be further subdivided into: the paper is transported from the stacking paper table to the front paper feed portion of the front gauge, and the paper is handed to the delivery paper by the front gauge and passed through three times. After the imprint is completed, the transfer section is transferred. The key to "accurate registration" lies in the transfer of printed sheets. 
The mechanical structure of the front paper feeding section is relatively simple and the adjustment is not difficult. It is required that the primary worker should master the correctly adjusted technology. The essentials are as follows: The operating procedures must be strictly regulated; the air pump can work normally and the wind is sufficient; the stacking paper table is horizontal, the height of the paper pile meets the requirements (lower than the take-up roller 5~8mm); the moving and static parts are in the standard position; Neat, smooth, vertical, moderate (before the paper, turn the stack of axially adjustable screws to the center point), output side of the paper near the side of the file, should be about 5mm from the side fence, properly handle the paper; wind Adjusted to moderate (song paper blowing mouth can open the surface layer of 6 ~ 8 paper mouth, scattered without mess; pressure paper blowing nozzle to the paper bite paper angle slightly floating can be; points, delivery paper suction nozzle can suck The paper can be used); the accessories on the splicing roller on the rubber roller and the paper feeding board are symmetrical and can be pressed without death; the rotation is flexible; the line belts are equidistant and the paper tightness is consistent; the brush roller does not press the paper tail; The main and auxiliary machines meet the requirements (before the file reaches the working position, the first sheet should be sent to the distance gauge 3~5mm). (To be continued)