Application principle of inkjet technology in the

The application principle of inkjet technology in the bill industry

as customers' personalized and digital needs for prints become more and more extensive, more and more printing enterprises have focused on digital inkjet equipment. The quota scraping invoice launched nationwide and the roll invoice to be launched soon are also printed with digital inkjet equipment; Various random numbers, bar codes, two-dimensional codes and other variable data will be more widely used in domestic commercial paper with a displacement speed of 5mm/min. All these promote the domestic bill printing industry to develop rapidly in the direction of digitalization, and also make digital printing equipment more popular

more and more foreign suppliers of digital inkjet printing equipment have also targeted China, a great market, and have entered one after another, giving demand enterprises more and better choices

1. Inkjet principle

at present, the inkjet technologies used in the industrial production of the bill industry are roughly divided into two categories: thermal inkjet technology and piezoelectric technology

thermal inkjet technology uses micro resistors to rapidly heat a thin layer of ink, so that a small part of the ink evaporates to form bubbles. Through the nozzle, the ink and the air in the ink channel are sprayed at the specified position at a high speed to print images or numbers, bar codes, QR codes and other numbers. The forming technology adopts a production process similar to the integrated circuit, which consumes less ink, is easy to use, has high inkjet frequency and precise inking position control, so it can print high-quality prints at high speed

thermal inkjet technology nozzles used in industry are generally designed as heavy-duty equipment that can work continuously for 24 hours and adapt to different production environments

piezoelectric technology uses piezoelectric crystals to push the nozzle diaphragm to eject ink. This technology utilizes the actual transfer of a large number of diaphragms for inkjet. Because the air particles in the ink channel will have a certain impact on the quality of piezoelectric printing, it is easy to block and leak ink. It is necessary to often spray some ink to flush the nozzle to eliminate the air particles in the channel. It also takes a certain amount of time to clean the nozzle every time you start the machine. It will cause a lot of waste of ink for a long time

2. The structure of components brings special challenges. Ink jet head structure

the ink cartridge and nozzle using thermal ink jet technology are integrated structures. When the ink is used up, the ink jet head needs to be replaced at the same time when the ink cartridge is replaced, so there is no need to worry about the phenomenon of ink blockage and ink leakage, which can ensure that the printing results are always clear and excellent. Because the nozzle is disposable, its manufacturing cost is relatively low. Except for the nozzle, there are no moving parts, and the mechanical loss is very low

the nozzle and ink cartridge of the inkjet head made of piezoelectric technology are of a split structure, and the manufacturing cost of the nozzle is very high. After the ink is used up, only the ink cartridge needs to be replaced, and the nozzle needs to be cleaned frequently without replacing the nozzle; The service life of the nozzle is longer than that of the thermal inkjet technology, but it is prone to ink blockage and ink leakage; When the service life of the nozzle expires, it needs to be replaced with a new nozzle before it can be put into use again

3. Production cost

although the cost of the nozzle using thermal inkjet technology is much lower than that of the piezoelectric technology, because the nozzle and ink cartridge of thermal inkjet technology are connected, the cost of replacing the ink cartridge is slightly higher than that of the piezoelectric technology. However, because the nozzle of thermal inkjet technology does not need maintenance, and there are no redundant motor parts, there is no replacement cost of vulnerable parts and parts

for the nozzle with piezoelectric technology, the cost of ink is relatively cheap, but the cost of cleaning and maintaining the nozzle is high; In addition, vulnerable parts and parts need to be replaced

in terms of the overall production cost, the nozzle of thermal inkjet technology is slightly lower than that of piezoelectric technology

4. Inkjet accuracy

inkjet accuracy is determined by horizontal accuracy and vertical accuracy, which plays a decisive role in the quality of prints. In bill printing, high accuracy is not only for the beauty of the printed matter. For example, the variable numbers that need to be identified, such as spray printing bar codes and two-dimensional codes, have high requirements for accuracy. If the normal recognition accuracy cannot be achieved, then the products that are sprayed are products with quality problems

the horizontal accuracy of bar code recognition and QR code recognition is determined by its horizontal accuracy. The horizontal accuracy of bar code recognition should be more than 240dpi, while the horizontal accuracy of QR code recognition should be more than 300dpi

the nozzle density of thermal inkjet technology is very high, which can achieve high inkjet accuracy. Piezoelectric technology can also achieve high inkjet accuracy

at present, in the bill industry, there are strict standards for the stamping properties of stainless steel materials in some utilization fields, such as machinery manufacturing, automobile and ship plates, etc. if the stamping properties are not qualified in the process of mechanical forming, it is easy to cause the cracking of stainless steel plates, which seriously affects the product quality. The inkjet system has been deliberately applied to all bill printing, in order to promote the digitization process of the whole bill industry. It can be said that the digital printing system will gradually eliminate the original mechanized equipment and become a necessary equipment in the bill industry. It will eventually enter a completely new digital era

printing technology

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