Lithographic Offset Balance Control Control (3)

V. Analysis of the phenomenon of imbalance of ink and water balance How to achieve ink-water balance, operators must not only understand and study the organic links between ink and water, their mutual constraints, and the law of subtle changes between them. They should also analyze and explore the imbalance of ink and wash. At the time of the adverse consequences.

1 The phenomenon of small water and small ink is analyzed: In the printing process, there is a certain water film on 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 it is too small, the amount of water layer can not resist the adsorption of ink on the blank part, then the blank part will be accompanied by ink, resulting in hanging dirty, less ink supply will make the printed product with no gloss, pale gray, imprinted, The imprint is filled with snowflakes and white spots. In this state, although the "ink balance" has also been achieved, this "ink-and-ink balance" is not the "ink-ink balance" we want.

2 Analysis of the phenomenon of water, water, ink and more: At this time, the ink is most likely to be unevenly printed, dirty, and a certain part or large area of ​​the layout will cause paste and paste. The printed products become black and dark, and the outlets are not clear, especially for the reproduction of subtle outlets, and the images cannot be clearly separated.

3 Analysis of the phenomenon of water, ink and less: If the water content of the layout is too large, gradually spread to all the surface of the ink roller to form a certain thickness of the water layer, which hinders the ink to accelerate the emulsification speed of the ink, and the blotting ink gradually becomes unsaturated. The text becomes lighter, and the writing is imaginary, grayish, hairy, hairy, and dull. There is a faint ambience around the blot, the image is not clear, and there is no hierarchy.

4 Analysis of the phenomenon of water, ink, and more: When the water in the layout is excessive, the ink color will become shallow, and the amount of ink supply will be blindly considered to be low, thus increasing the amount of ink, and the ink will lose its stability after a long cycle. The vicious cycle of ink and ink imbalance leads to severe emulsification of the ink, which accumulates on the surface of the ink roller, making printing impossible.

Sixth, ink balance of commercial rotary machines

As a commercial rotary machine, ink and water balance should mainly be controlled from the following aspects:

First, what is ink? The purpose of using the 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 expansion of the ink on the graphic image to the blank part to prevent the dirty plate; to supplement the hydrophilic layer damaged in the printing process , Maintain the hydrophilicity of the blank part of the printing plate; Reduce the surface temperature of the printing plate. Rotary water is made up of pure water, fountain solution and alcohol. The use of pure water can avoid algae formation on the dampening water pipe wall and cause obstruction. Alcohol consumption is 8 to 11%. The fountain solution has a conductivity of 9-11 and a pH of 4.8-5.2. The state of these values ​​is the best. It depends on the operator's long-term practice and summary. The ink is dispersed in the binder by very fine pigments and fillers, and after grinding, it becomes a more stable fluid colloidal suspension. The commercial rotary ink is generally a thermosetting type (ie, a heat-dried ink), and its drying performance, oil content, and water-soluble latitude are greatly different from the oxidation-drying ink and the adsorption-drying ink. With large latitude, low water content, low latitude, and difficulty in grasping the degree of ink emulsification, ink manufacturers are generally required to provide matching (adaptive) fountain solution, because it has obtained the best formula through several professional experiments and production. And we need long-term exploration to master it.

Second, the operator's mastery of the printing plate and his ability to understand the proofs. Check whether the printing plate outlets and field density meet the requirements and whether it meets the requirements for rotary printing. Due to the high speed of rotary printing (generally up to 30,000 rev/hr or more) and the B-B type, if the print body is not enough ink, and the black layer of the proof is thicker, the operator needs to zoom in to get closer to the sample ink. Ink volume, in this way, excess ink accumulates more in the ink roller, which can result in ink ejection or ink emulsification. This can cause the ink to become dirty and damage the balance of ink and ink. After that, increasing the amount of water is no help. In addition, products printed by rotation are not required to be inked. As long as they are saturated in the field, if they do not analyze the difference between the proofs and the actual printing, they will increase the amount of ink blindly, which in turn will cause print quality problems.

Third, the adjustment of water glue. The adjustment of water glue is more critical, especially the adjustment of the water transfer roller and the printing plate glue requires moderate adjustment of the water glue (with printing plate printing width of 8 ~ 9mm, and water transfer roller printing width of 5 ~ 6mm), Being too big or too small is not conducive to water transfer. What's more important is that both ends must be leveled. If the two ends are not even, then at the time of printing, one end of the water will be large and one end of the water will be small, so that when the ink balance at the small end of the water is good, then the water at the other end must be large. If you reduce the water at the same time, the other end will damage the ink balance due to water, resulting in a dirty version. In short, if water glue is not leveled, then water or water will be small, which will result in serious emulsification and fail to achieve the best state of ink balance. The same applies to the adjustment of ink.

(to be continued)