Control of fountain solution in the most popular m

2022-08-08
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Control of fountain solution in modern offset printing

in offset printing, the water on the printing plate is first wetted by the plate water roller, the blank part of the printing plate is hydrophilic and adsorbs a certain amount of water, and the graphic part is lipophilic and does not adsorb water; When the printing plate is inked by the plate inking roller, a certain amount of ink will be absorbed in the graphic part. Then, through embossing, water and ink are transferred to the paper through the plate cylinder and rubber cylinder. The difficulty in this process is ink balance, and fountain solution is the key

composition and function of fountain solution

the selection of fountain solution should be very careful, and it should be checked whether it has the following components: buffer, plate protector and wetting agent. Preservatives, desiccants. Biocide and anti foam agent, etc. Slow; The medium agent mainly plays the role of stabilizing the pH value of the fountain solution. Because the fountain solution is generally acidic, the pH value of the fountain solution will fluctuate greatly with the change of the buffer addition amount of s=0.001mm. Improper addition amount will affect the service life of the printing plate (corrosion of the printing plate). In addition, it will make it difficult to dry the ink, especially the ink containing metallic pigments

during the printing process, the fountain solution has been in contact with the printing plate, and the non graphic part (inorganic salt layer) of the printing plate will continue to dissolve, so that the printing test value cannot truly reflect the hydrophilicity of the used version, resulting in the phenomenon of dirty version. Plate protectants can continuously supplement the dissolved inorganic salt layer, maintain dynamic balance, and ensure the stable hydrophilicity of plates. Plate protectants also contain plate protection glue, so there is no need to wipe the plate in case of temporary shutdown

in the printing process, the less the fountain solution, the better, on the premise of not dirty the plate, so the wetting agent is very important. Wetting agent can reduce the surface tension of the fountain solution, so that the water is evenly distributed on the printing plate. A good wetting effect can be achieved with less fountain solution, as shown in Figure 1. Generally, the amount of alcohol added in the traditional fountain solution is more than 15%, while the modern new fountain solution contains wetting agent, which can greatly reduce the amount of alcohol

preservatives can protect metal parts, because the fountain solution is weakly acidic and corrosive to the metal parts of the printing machine; Desiccant can promote the drying of ink; Biocides can prevent algae and microorganisms from breeding in the waterway circulation system and avoid correct installation; Avoid pipeline blockage; Anti foam agent can prevent the formation of foam, because a large amount of foam in the water tank is not conducive to the wetting of the printing plate

modern new fountain solution should contain the above ingredients. In addition, users should also combine the water quality and other conditions of the printing plant to determine the hardness of factory water. Conductivity value and pH value shall be tested. The fountain solution manufacturer shall also provide applicable fountain solution and related parameters according to the water quality conditions of users. These control parameters mainly include the addition amount of fountain solution stock solution and isopropanol (alcohol). PH value and conductivity of fountain solution

use of fountain solution

the addition amount of fountain solution stock solution is generally controlled between 2% and 3%. However, if there is a lack of necessary measuring tools, or if the automatic extraction equipment fails, the operator often can only add it based on experience, which leads to many problems in the amount control of fountain solution

if the amount of fountain solution stock solution is too small, the printing plate is easy to get dirty and the adjustment time is long; It is difficult to achieve ink balance, and it is difficult to achieve satisfactory ink effect, which increases the risk of machine corrosion. If the amount of fountain solution stock solution is too large, the ink is easy to be over emulsified, and the ink color is not easy to control. It is used to measure the internal temperature near the square bottom of the drill cone; Ink throwing occurs. Ink flying phenomenon, polluting the water bucket and water roller; The ink roller is not inked, and the ink is easy to accumulate on the blanket

in order to solve these problems, standard measuring tools should be equipped when adding fountain solution manually to ensure quantitative addition; If there is an automatic adding device, it should be checked and maintained regularly to ensure its normal operation

when using modern new fountain solution, the amount of alcohol added should be controlled within 10%. General operators will think that the greater the amount of alcohol added, the less likely it is to dirty the version, so the amount of alcohol is always too large. In fact, when the amount of alcohol is too high, it will aggravate the dissolution of the paper surface, and printing products are prone to paper wool and paper powder; Ink is easy to be over emulsified, affecting the quality of prints

ph value and conductivity value are usually used to reflect and monitor the condition of fountain solution. The test shows that when the pH value is in the range of 4.8-5.3, the printing is the most stable, the service life of the printing plate is the longest, the printing quality is the best, and the balance of water and ink is the easiest to control. The pH value is not only determined by the amount of fountain solution, but also affected by the acidity and alkalinity of the paper. The conductivity should generally be controlled at (1400 ± 200) us, and the conductivity value is vulnerable to the hardness of water and the amount of alcohol. Due to the influence of dust and ink mixture, the conductivity value of 800-2000us is also allowed, but when the fountain solution looks obviously polluted, it must be reconstituted

in a word, if you control the hole solution well in the printing process, you will often get twice the result with half the effort

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