After many customers use the UV flatbed printer for a period of time, color bars appear on the printed screen. Usually, the cause of such problems is “head blockage”, which is the main factor affecting the screen quality and yield of the UV printer.
Discussing the reasons for the clogging of the head can help to better understand the machine and improve the picture quality of the printing.
The principle of the head is quite similar to the pump of bicycles that we often use every day. The iron rod of the pump that moves up and down is the soul component of our head—piezoelectric crystal. There are almost two reasons: the air circuit is blocked or the pumping iron does not work.
Of course, the head is much more complicated than the pump, so the reasons for “clogging” are also various, and there are roughly the following situations:
1. After the ink accumulates to a certain extent in the head, the head holes are blocked outside:
It is the most common blocking method, because the solvent in the ink must be evaporated into the air to dry the picture, so the ink is a volatile liquid, which is volatile in the air and clears out solids. When the head is spraying on cloth and objects, there will always be a part of ink left around it. After this part of the ink dries in the air, it will gradually make the head smaller or even block the head, but because it is outside the head, It’s easy to clean up, which is why we wash our heads so often.
2. Piezoelectric crystal damage:
It is certain that the print head cannot spray ink. The general piezoelectric print head can be used for about a year. It is normal that it may not be used for a year in a factory with a lot of printing workload.
3. Fatigue damage of piezoelectric crystal:
The phenomenon is that the head sometimes inks ink, and sometimes no ink is ejected, especially when the inkjet volume is large (that is, when spraying dark images), the phenomenon of “clogging” is obvious. At this time, the best method is to replace a new head.
4. The filter in the print head is blocked and the print head does not produce ink:
Using a print head for a long time, especially in factories where the printing task is not full and often shuts down at night, the ink does not flow in the print head for a long time, and it is easy to be adsorbed on the internal filter screen or the wall of the ink channel, so that the ink flow is cut off. The smaller area will also cause the ink out of the head. Now special equipment can help you solve this problem of the head.
5. The viscosity of the ink is too high or too low:
If the viscosity of the ink is too high, the fluidity of the ink is poor, and the amount of ink ejected by the head per unit time is not enough. , so that air is ejected; both will cause the phenomenon that the head does not run out of ink. In this regard, customers are often asked that the environment in which the ink is stored is very important. The ink should be placed in the environment where the ink is used for more than 24 hours before use, because the viscosity of the ink will be high at low temperature, and the viscosity will be higher at high temperature. It becomes very low, and the viscosity varies greatly. Once the inks with different viscosities are mixed together, it will cause the phenomenon that the ink cannot be ejected.
6. Failure of the drive circuit:
The aging of the electronic components of the driving circuit and the accumulation of too much dry ink dirt may affect the voltage driving the print head, resulting in the print head not producing ink or the amount of ink being unstable.
7. Types of ink:
Due to the improper control of the amount of desiccant, the ink of some manufacturers dries too quickly, which may easily cause the ink to block externally. Although it can be cleaned, the cleaning interval is relatively frequent. Once the print head is not used for a long time and the print head is not protected in time, the next time Reprinting may cause permanent damage to the printhead.
8. Frequent ink replacement:
When replacing the ink, in many cases, the head may not be properly protected, which will also affect the inkjet state of the head.
9. The ambient temperature and humidity of the machine use:
Generally, the recommended temperature is 22~25 degrees, and the humidity is 40~70%. The high and low temperature will affect the viscosity of the ink, which will cause the ink shortage of the head, which is often mistaken for “blocking the head”.
10. head driving voltage:
The appropriate print head voltage will make the print head ink more smoothly. The misunderstanding of the “clogging” of the printhead is that many people think that the ink particles are too coarse to clog the printhead, and it is safe to say that this is impossible unless you are a customer who is happy to remove the filter on the machine. Because before the ink reaches the head, it has to pass through the filter hole of the filter on the machine that is only one-tenth the size of the head hole. More importantly, the ink manufacturer must use a much finer filter than the filter on the machine. The filter substance filters the ink, why do it? This is highly specialized knowledge, and it is difficult to explain it in more detail here. Interested customers can discuss it individually.