"Inkjet coding" refers to a number of related technologies, and we use these techniques to eject very small ink droplets from the nozzles. The ink droplets pass through the air and finally land on the surface of the printed material to form a printing pattern. Valve type printing This method is the easiest to achieve, in the past 20 years, mainly used in the outer box printing.
A valve print apparatus includes a low pressure ink system, an electronically controlled chassis, and a spray head attached to the chassis with a flexible conduit. The ink in the ink system is sent through a simple opening/closing valve to the nozzles in the spray head (a spray head typically has 7 to 18 200 micron diameter nozzles or more). When an ink droplet needs to be ejected, the electronic component opens the corresponding opening/closing valve and the ink droplet is ejected. Due to the simple mechanical structure, the valve type printing system is easy to establish. Customers typically select suppliers by comparing the user interface (ie, whether the operation is easy), the print capability/print diversity/quality, and the applicable ink series. The print quality of valve printing is not stable. This is because the ink stays in the nozzle until it is ejected. If the ink dries in the pipe, it will block. The system works best with water-based inks that print on osmotic surfaces. Many valve-type printing system manufacturers produce non-permeable surface inks that dry faster than water-based inks. Blocking occurs and the drying time is still quite long—about 15 to 30 seconds. In general, if the print quality requirements are not high and the nozzles are frequently cleaned, the valve printing system can perform well. Although the cost of acquisition is relatively low, the cost of the use of the valve jet printing system is higher after one or two years, so this technology has gradually been replaced by pulse jet printing technology. Pulsed jet printing technology is mainly divided into two types:
Piezoelectric inkjet printing and bubble jet printing - the realization of these two technologies is very different. Pulsed inkjet printheads have evolved from the field of office printing - pulsed printing is now widely accepted in the office printing industry and has excellent results.
Pulse printing
Although pulsed jet printing is conceptually simple, it is worth noting that it was not until the 1970s that some people obtained the initial patent, and although Canon, Hewlett-Packard and other companies did a lot of research until the 1990s, Cheaper products are available on the market. So pulse-jet printing is not as simple as it seems. There is still a lot to be done in the office from printing at a fixed distance to clean paper to inkjet printing in the harsh environment of the factory.
Piezoelectric jet printing First of all, the piezoelectric jet printing technology is piezoelectric printing. Simply put, the ink pressure in the nozzle must be low enough (or negative pressure) because the surface tension of the ink keeps the ink at the nozzle. In the printing process, a pulse voltage is applied to the piezoelectric crystal and the piezoelectric crystal is deformed to reduce the volume of the nozzle ink chamber. In this way, a drop of ink is ejected from the nozzle. Then, the piezoelectric crystal returns to its original state, and new ink enters the nozzle due to surface tension. By arranging a large number of nozzles side by side, the ideal print width and resolution (typically 8-6 dots/mm) can be achieved. Although the print resolution can be increased by tilting the print head (which sacrifices the print height), the print resolution is fundamentally determined by the nozzle pitch. More sophisticated improvements can make each piezoelectric crystal drive more nozzles (such as 8), 32 piezoelectric crystals can drive 256 nozzles of ink, so that there will be a larger range of printing, of course, in the There are only 32 programmable placement points on the print surface. Because the system is not continuous, the ink must remain fluid in the nozzle and dry on the printed surface. The inks used in piezoelectric ink jet printing are usually oil-based or paraffin-based. These two types of inks do not dry out in the nozzles, but they can be absorbed by the printing surface. Piezoelectric jet printing also uses some quick-drying inks. Fast-drying inks still take a long time (about 10 seconds) to dry out. When the product needs to be processed quickly and printing is prohibited after the printing, the use of quick-drying ink can cause problems. In order to prevent the ink from drying out in the nozzle, we can also apply a lower pulse voltage to the piezoelectric crystal. This will cause slight disturbance to the ink in the nozzle and the ink in the nozzle will not dry out. This method relies on changes in the ink composition or mechanically more sophisticated improvements. Another method to achieve piezoelectric printing is to heat the print head while using a hot melt ink. In this way, the ink remaining fluid in the nozzle solidifies on the surface of the colder printed object. The piezoelectric print system can achieve good results on many printed surfaces, but it is easily scraped off during touch. In addition to the problem of the ink drying out in the nozzle, another problem that needs attention is that the nozzle is sensitive to vibrations. The vibration can cause the ink to be ejected out of the nozzle and the ink chamber so that the surface tension cannot cause the ink to fill the nozzle. The system must then be restarted. Obviously, the print quality has been affected when vibration problems are discovered.
