V. Analysis of the phenomenon of imbalance of ink and ink How to achieve ink and ink balance, the operator must not only understand and study the organic relationship between ink and ink, the constraints between each other and the rules of subtle changes between them, but also analyze and discuss the imbalance of ink Adverse consequences caused by time.
1 Analysis of the phenomenon that there is little water and little ink: In the printing process, there is a certain water film in the blank part of the printing plate. When the water film and the oil can contend, it will not be stained by the ink on the ink roller. If the amount of the water layer is too small to resist the adsorption of the ink on the blank part, the blank part will adhere to the ink, resulting in hanging dirt, and the amount of ink supply will make the printed matter dull, light gray, and the imprint is not true. The blots are covered with snowflake-like white dots. In this state, although the "water-ink balance" is also reached, this "water-ink balance" is not the "water-ink balance" we want.
2 Analysis of the phenomenon of less water and more ink: At this time, the ink color of the printed product is most likely to be uneven, hanging dirty, a certain part or a large layout is caused by water shortage, resulting in paste and paste. At the same time, the printed ink is darker. Makes the printed matter dark, the dots are not clear, especially for the reproduction of fine dots, the image is not clear.
3 Analysis of the phenomenon of less water and ink: If the water content of the plate is too large, it will gradually spread to all the ink roller surfaces to form a water layer of a certain thickness, which hinders the normal transfer of ink. The emulsification speed of the ink is accelerated, and the color of the printed ink is gradually unsaturated. The picture becomes lighter, the handwriting is dull, gray, hairy, hairy, and dull. There is a halo around the imprint, the image is not clear, and there are no layers.
4 Analysis of the phenomenon of large amount of water and ink: When the water content of the plate is excessive, the ink color will become lighter, and it will often blindly think that the amount of ink supply is small, so the amount of ink is continuously increased, and the long-term circulation back and forth, the ink emulsification loses stability, causing The vicious cycle of water-ink imbalance leads to serious emulsification of the ink, which accumulates on the surface of the ink roller, making printing impossible.
6. Ink and ink balance of commercial rotary machines
The balance of water and ink as a commercial rotary machine should be controlled from the following aspects:
First, what is ink. The purpose of using fountain solution in offset printing is mainly to: form a water film that repels ink in the blank part of the printing plate, to resist the expansion of the ink on the graphic to the blank part, to prevent the dirty version; to supplement the hydrophilic layer destroyed during the printing , Maintain the hydrophilicity of the blank part of the printing plate; reduce the surface temperature of the printing plate. The water used in the rotary machine is composed of pure water, fountain solution and alcohol. The use of pure water can prevent algae from forming on the walls of dampening water pipes, causing blockage. The alcohol consumption is 8 ～ 11%. The conductivity of the fountain solution is 9 to 11, and the pH is 4.8 to 5.2. Under what conditions these values ​​are best, we must rely on the operator's long-term practice and summary to grasp. The ink is dispersed in the binder by very fine pigments and fillers, and becomes a more stable fluid colloidal suspension after grinding. The commercial rotary ink is generally a thermosetting type (that is, thermal drying ink), then its drying performance, oil content, and water tolerance are very different from oxidative drying ink and adsorption drying ink. The tolerance is large, the amount of water is not easy to master, the tolerance is small, and the degree of emulsification of ink is not easy to master. Generally, ink manufacturers are required to provide a matching (adapting) fountain solution because it has obtained the best formula after several professional experiments and production. And we need long-term exploration to master.
Second, the operator's ability to master the printing plate and understand the proofs. Confirm whether the dots and solid density of the printing plate meet the requirements and whether they meet the requirements of rotary printing. Because the rotary printing speed is fast (generally more than 30,000 rpm), and it is type B-B, if the printed version does not consume enough ink, and the black layer of the proof is thicker, the operator can only zoom in to get closer to the proof ink color. The amount of ink, so that the excess ink accumulates in the ink roller, the ink will be thrown away or the ink will be seriously emulsified, which will cause the printed product to become dirty and destroy the balance of water and ink. Afterwards, increasing the amount of water will not help. In addition, the products printed in rotation do not require large ink, as long as the field is saturated, if the difference between the proof and the actual printing is not analyzed, the amount of ink will be increased, which will cause print quality problems.
Third, the adjustment of water glue. The adjustment of the water glue is more critical, especially the adjustment of the water transfer roller and the plate-based water glue requires moderate adjustment of the water glue (with the printing plate ink width of 8-9mm, and the water transfer roller ink printing width of 5-6mm), Too large and too small are not conducive to water transfer, more importantly, the two ends must be leveled. If the two ends are not flat, then when printing, there will be a large water at one end and a small water at one end, so when the water and ink balance of the small water end is good, then the water at the other end must be large. If the water is reduced at the same time, the other end will destroy the water-ink balance due to the small water, resulting in a dirty version. In short, if the water glue is not leveled, then there will definitely be large or small water, resulting in serious emulsification and not reaching the optimal state of water-ink balance. The same is true for the adjustment of ink glue.
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