How to solve the problem of printing offset caused by UV offset printing

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. The control of the workshop environment is to keep the humidity between 50% and 60%, the summer temperature is between 20-220C, and the winter temperature is between 22-250C. The UV printing of the offset printing workshop will generate a lot of heat, and the control of the temperature and humidity is to ensure printing. The first condition of quality.

2. Formulation of fountain solution At present, UV offset printing is generally used with alcohol or isopropyl alcohol fountain solution. In comparison, alcohol can be quickly volatilized, which can effectively transfer the heat generated by friction between the printing plate and 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. Too acidic, can cause serious forum on dirty, graphic basis because of the erosion caused by the flower version, easily emulsified ink, ink roller easy to produce de-inked, printed ink dark and dull; acidity is too small, easy to make the ink forum 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 main cause of fouling on the front and back is the lack of 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 unevenness and unevenness in the ink may sometimes occur in the dark shaded printing. The longer the printing machine 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) The wavy longitudinal stripes and pale stripes appear in the fault printing of the fountain solution. In the case of determining that the reversing 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.