Understanding of Domestic Printing Card UV Offset (II)

Printing adjustment
1. Workshop environment control
Maintain humidity at 50% to 60%, summer temperature at 20～22°C, winter temperature at 22～25°C, UV printing in offset printing workshop will generate a lot of heat, control temperature and humidity is to ensure printing quality primary condition.

2. Formulation of fountain solution
At present, UV offset printing generally uses alcohol fountain solution or isopropyl alcohol fountain solution. In comparison, alcohol can be quickly volatilized, which can effectively transfer the heat generated by the printing plate running and the friction of the ink roller. It is recommended to use an alcohol fountain solution with a concentration of 10% to 12% and a temperature of 5 to 10°C.

The pH value of the fountain solution is particularly important, and the pH value should be increased as much as possible to ensure that the plate is not dirty. The UV offset printing is generally controlled at a pH of 5.6-6. If the acidity is too strong, the layout will be heavily visceral, the graphic and text will be eroded and the pattern will be eroded, the ink will be easily emulsified, the ink roller will be easily deinked, the ink will be dark and dull, and the acidity will be too small to make the ink Loss of balance, non-graphical part of the hydrophilic and oil-repellent weakened, the layout from the dirty, due to the increase in print outlets caused by paste version. Therefore, the control of the fountain solution pH plays a key role in printing.

3. Common printing failure
(1) Flying ink
UV inks have large viscosity and poor fluidity. However, when the room temperature is high or the humidity is too low, the printing press runs at high speed for a long time, which causes the ink viscosity to become smaller, the fluidity increases, and flying ink droplets to be generated. This time should be reduced. Room temperature, increased air humidity, and constant low speed printing.

(2) Lamo
When the UV printing field version is easy to produce ink pull phenomenon, the main reason is the improper choice of printing surface; cold machine open, the machine's UV ink roller temperature is too low or ink viscosity is too large. The printed surface of PVC and other sheets should be properly selected; let the machine idle and warm up, and apply some thinner on the ink roller; in winter, pay special attention to the temperature change of the UV ink roller of the machine. In addition, under the premise of not affecting the quality of the card, some inks with low viscosity and strong fluidity can be selected for printing.

(3) The front and back are dirty
The main cause of stickiness is insufficient ink curing, especially black ink. In addition to effectively controlling the pH of the fountain solution and controlling the ink balance, it is also necessary to check whether the power of the UV lamp is within the effective range. The printing speed should not be too fast. Generally, a single-layer card printing is preferred at 6000 printing/hour. The ink is preferably matched to the wavelength of the UV lamp.

(4) Ink shades are uneven
Ink printing and squeezing can sometimes occur unevenly in printing. The new machine basically has no such phenomenon. The longer the printing machine is used, the more obvious the problem is. Appropriate machine adjustments will change. To effectively control the ink balance, adjust the machine's water, ink roller pressure. In addition, it is also possible to adjust the position of the ink oscillating roller, that is, the position of the initial static point in the lateral turbulence of the ink roller and the ink roller. When adjusting, it is necessary to gradually adjust the micro adjustment so as to obtain a relatively satisfactory printing effect.


(5) Failure of fountain solution
There are wavy vertical stripe and pale stripe in the printing. Under the condition that the printing roller is in good condition, the amount of IPA is often too much. In this case, the amount of IPA can be reduced and diluted with clean water. The appearance of thick vertical stripes, often with too little amount of IPA, at low IPA or no IPA, the concentration of fountain solution becomes lower, and corrugations and longitudinal stripes are most likely to occur.

Print design
For the print quality of the card, the print design is also critical. Because the UV offset printing of the printing card is more prone to dot gain than the paper printing, the manuscript with superior design effect is greatly dissimilar to the design intention after printing on the machine, and the color is gray. Dot enlargement is a key factor affecting color. An excellent designer, in addition to understanding the principle of print design, understands and grasps the extent of changes in the card's Internet site after printing is also crucial. When designing, taking into account the changes in printing, will be able to print a more beautiful card pattern, which requires the designer to continue to accumulate.
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