Printing UV offset printing problems appear to solve the common problems

After learning about the type of offset press and the type of printing materials needed for UV offset printing, we need to look at what kind of requirements are needed for the printing environment and supporting products.

1. Workshop environment control

Keep humidity at 50% to 60%, summer temperature is best at 20-220C, winter temperature is best at 22-250C, UV printing of offset printing workshop will generate a lot of heat, and controlling temperature and humidity is the most important condition for guaranteeing printing quality. .

2. Formulation of fountain solution

At present, UV offset printing generally uses alcohol or isopropyl alcohol fountain solution. In comparison, alcohol can be quickly volatilized, which can effectively transfer the heat generated by the operation of the printing plate 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 100C.

The pH value of the fountain solution is particularly important, and the pH should be increased as much as possible to ensure that the plate is not dirty. The pH of the UV offset is generally controlled at 5.6 to 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

The UV ink itself has a large viscosity and poor fluidity. However, when the room temperature is high or the humidity is too low, the printing press runs at a high speed for a long time, the viscosity of the ink becomes smaller, the fluidity increases, and scattered ink droplets are generated, which should be reduced at this time. 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 selection of the printing surface: cold machine open, the machine's UV ink roller temperature is too low or ink viscosity is too large. The printing surface of PVC and other sheets should be selected correctly: Let the machine idle and preheat, 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 the premise of not affecting the quality of the card, some inks with low viscosity and strong fluidity are selected for printing.

(3) The dirt on the front and back

The main cause of stickiness is insufficient ink curing, especially black ink. In addition to effectively controlling the pH of the printing solution and controlling the ink-water 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. It is better to print a single-layer card at 6000 printing/hour. The ink used is best. Match the wavelength of the UV lamp.

(4) Ink shades are uneven

There are occasional ink shades in the print and the drag. The longer the printer is used, the more obvious the problem is. To effectively control the ink balance, adjust the machine's water, ink roller pressure. The position of the oscillating roller can be adjusted, that is, the initial static position in the horizontal pulsation of the ink roller and the ink roller. When adjusting, it is better to pay attention to the gradual adjustment of the trace, and adjust it 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 stripe is often due to too little IPA. In the absence of IPA, the concentration of the fountain solution becomes lower, and ripples and longitudinal stripes are likely to appear.