Fault keywords: Dirty, thick, dirty, dirty, paper-pulled paper, no crystallizing, ink flying, ink drying, too fast, network expansion
The various failures that occur during the printing process are generally seldom caused by a single factor, and are mostly caused by the uncoordinated and mutual influence of ink, paper, printing machine and printing environment conditions. Here are some common printing faults, from the ink point of view to provide solutions for your colleagues reference.
1. Dirty
Dirty refers to the occurrence of many ink stains in the non-graphic area of ​​the printed matter, which is a common and typical failure in lithography.
This phenomenon is mostly caused by various factors such as ink, paper, printing plate, printing potion, etc. From the perspective of ink, it usually occurs when the ink is thin, soft, too high in yield value, and insufficient viscosity. To improve the ink The performance, adding appropriate amount of resin viscosity adjustment ink or gloss paste with greater viscosity, helps to overcome the dirt; when the ink is prepared, the amount of desiccant, low viscosity adjustment oil, and detackifier is added too much, and the ink adjustment is thin The viscosity is small, which is an important reason for this disadvantage. If the ink is properly prepared, it can be solved. Change to fast solid ink.
Secondly, uneven sanding of printing plates, residues of abrasive materials, insufficient non-fat sensitization, partial oxidation of plates, or insufficient development, etc., are also important factors causing soiling, and should also be checked and resolved. At the same time, the roller arrangement of the printing machine is poor If the water roller is dirty, the rubber of the ink roller is aging, and the blanket is loose, it will also cause dirt. It should be checked and adjusted.
2. Thickness
Thickness means that the pigment separates from the ink and accumulates on the plate and blanket, which results in the dots of the printed matter stagnation.
In general, the ink is poor in water resistance, and this phenomenon often occurs when it is easy to emulsify. Appropriate amount of high-viscosity resin ink, gloss paste or printing varnish can be added to improve the viscosity, transferability and water resistance of the ink, while increasing the PH value of the printing potion, reducing the amount of water supply, reducing the amount of ink supply, can be improved Or overcome this failure.
3. Scratch dirty, also known as "stained", "stained back", the printing speed is too fast, the ink printed on the paper is not fixed enough time or the stack pressure is too large, the ink layer has not been dried, the ink re-occurs The transfer phenomenon is called rubbing.
This phenomenon is easy to appear in high-speed four-color and two-color printing. The most basic measure is to use fast solid light, fast solid ink printing and powder spraying, adjust and control the amount of powder spraying, and reduce the supply of ink when the color and density of the ink allow The amount of ink reduces the pressure on the accumulation of printed products and reduces the amount of water supply, which helps to overcome the phenomenon of smudging.
4. Paste
Paste edition refers to the phenomenon that the ink appears in a very light color in a large area in the blank space of the layout during the printing process, and it will quickly appear in other places after being wiped off.
The occurrence of paste-up phenomenon is generally due to poor water resistance of the pigment in the ink, improper adjustment of the ink formula, excessive use of the debonding agent and low-viscosity ink, and the ink is too soft and too thin to cause paste. To solve this problem, one is to choose inks with good water resistance, and the other is to adjust the amount of various printing auxiliaries to ensure the ink's water resistance and water-ink balance.
5. Pull paper wool
Printing high-grade coated paper, glass cardboard, matt paper, this problem generally does not occur. If the surface of the paper is rough, the strength is not good, the adhesion of the coating of the paper is not strong, and the viscosity of the ink is relatively too large, it can cause the phenomenon of pulling the paper and cause the printing quality to decline. In this case, it is a simpler and more economical method to reduce the viscosity of the ink with a debonding agent or to use an ink with a viscosity as small as possible, so that the ink film is easily split during printing, and reduce the printing speed. better.
6. Crystallization
Crystallization is also known as vitrification. The phenomenon is that after the ink printed first is dried, the ink can not be printed when printing, or even if it is printed, the ink layer is easy to fall off after drying. The fast curing light ink and resin offset ink after the resin is resinized This kind of problem is rare, and this phenomenon occurs occasionally when printing on large solid areas or when the ink layer is too thick. The solution is mainly to reasonably control the overprinting time of the next color, and to overprint when the previous color is not completely dry. Second, to control the amount of dry oil. Too much dry oil is the main factor to promote crystallization.
7. No ink
Inklessness, also known as de-inking roller, refers to the phenomenon that streaks appear in the printed matter and the hue is relatively light.
This phenomenon is mainly due to the poor ink quality of the ink, the yield value is too high, the pigment content in the ink is too high, the ink head is too short to become cheese-like, the ink has gelled or the water has entered the ink, causing part of the flocculation, which causes The ink in the ink tank of the printer is separated from the ink roller and cannot be transferred well. When encountering this problem, we must first improve the ink properties and ink fluidity from the ink design. Secondly, when printing, properly adjust the ink with high viscosity to improve the fluidity of the ink, which can help to overcome the ink with greater thixotropy and acceptable viscosity and fluidity. The ink in the ink tank is often stirred with an ink knife or Installing a stirrer directly in the ink tank can also overcome this disadvantage.
8. Flying ink
Ink flying means that the ink is between the rotating ink rollers during printing, and the ink filament that is broken when separated becomes charged small particles due to the surface tension and is expelled in space by the running printing machine. phenomenon.
The phenomenon of flying ink increases significantly with the thickening of the ink layer of the roller and the speed of the printing press. When it is serious, it pollutes the equipment and the printing environment and even affects the quality of the printed product. This kind of phenomenon occurs mainly because the viscosity of the ink is not compatible with the speed of the printing machine. It is generally caused by the viscosity of the ink, the length of the filament head, and the softness of the ink. The ink has poor water resistance, and the ink flying phenomenon can also occur when it is easily emulsified. The main solution is to reduce the viscosity of the ink and improve the water resistance of the ink. Use harder and denser ink to reduce the amount of ink supplied, the ink layer of the roller is thin, and the phenomenon of flying ink will be improved.
9. Dry too fast
Drying too fast means that the ink thickens and dries in the ink fountain, on the ink roller, and on the blanket.
This phenomenon is mainly caused by too much desiccant in the ink, and the ink contains more solvents that volatilize too quickly; the temperature in the printing workshop is too high, the air is too dry or the air circulation is too good. The solution is mainly to add a small amount of petroleum jelly to the ink to reduce its conjunctiva drying speed; add a small amount of anti-skinner or antioxidant; workshop ventilation should not be too good.
10. Expansion of outlets
The dot expansion is mainly manifested in the dots on the plate, which cannot be faithfully reproduced. As a result, the dots are deformed or connected, and the contrast is insufficient, which affects the quality of the print.
This phenomenon is mostly caused by improper ink preparation, too thin and too soft ink, and insufficient concentration. When the ink is prepared, an appropriate amount of debonding agent should be added instead of a thinner ink, or a higher concentration of ink should be used to reduce the amount of ink. This phenomenon can be overcome. Secondly, the hardness of the ink roller of the printer is not suitable. The pressure of the roller is too large, the blanket is loose, and the arrangement of the rollers is also an important reason for this problem. It is also due to inspection and adjustment.
Ink and printing workers are very clear that there is no universal ink, which can adapt to various printers, papers, printing environments and different printing needs. Therefore, it is necessary to adjust the ink according to different situations during printing. It is also very important. Proper deployment can reduce a lot of printing failures. The above is only for your peers' reference, hope to correct me!
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