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Principles of digital inkjet printing


2021-10-12


I often talk to you about digital printing, but have you changed the principle of inkjet printing after watching it for so long? It is estimated that there is not much that I really understand. Today I will talk about the principle of digital inkjet printing, so that everyone can understand more about digital printing.
The working principle of digital inkjet printing technology is simply to apply external force to the ink so that it can be sprayed onto the fabric through the nozzle of the print head to form a color dot. Digital jet printing is the jetting technology of digital images. The digital technology controls the nozzle’s spraying or not, which color of ink to spray and the movement in the X Y direction, to ensure that the required image and color are formed on the surface of the fabric. An important technical indicator of digital printing is resolution (referred to as dpi), which refers to the number of dots per inch. In inkjet printing, different base fabrics have different requirements for resolution. Generally, when the dpi is 180~360, the image is clear. For very fine images, the dpi can reach 360~720. After the resolution is improved, the requirements for the spray frequency and orientation accuracy of the nozzle are higher. Dyeers Wujiang’s Digital Printing Zone also summarized some discussions on the resolution of digital printing.
The principle of jet printing:
1. CIJ (continuous Ink Jet)
The principle of continuous jetting is to apply high-frequency oscillating pressure to the printing ink, so that the printing ink is ejected from the nozzle to form a uniform and continuous flow of droplets. An electric field that changes synchronously with the pattern photoelectric conversion signal is provided at the nozzle. The ejected droplets are selectively charged in the charging electric field. When the flow of droplets continues to pass through the deflection electric field, the charged droplets are deflected under the action of the electric field, and the uncharged droplets continue to maintain a straight flight state. The droplets flying in a straight line cannot reach the substrate to be printed and are recovered by the liquid collector. The charged droplets are ejected onto the substrate to be printed.
2. On-demand DOD (Drop on Demand)
The working principle of the on-demand jet printing system is that when printing is required, the system applies high-frequency mechanical force and electromagnetic thermal shock to the color ink in the nozzle to form tiny droplets that are ejected from the nozzle, and the jet is controlled by the computer. Go to the set pattern. On-demand jetting is the most widely used thermal inkjet technology, which relies on heat pulsation to generate ink droplets, and a computer controls a heating resistor wire to a specified temperature, causing the ink to vaporize (mist) and then eject from the nozzle. Another kind of DOD technology is a piezoelectric ejection system, which is controlled by a computer to impose a potential on the piezoelectric material, which causes the piezoelectric material to compress in the direction of the electric field and expand in the vertical direction, so that the ink is ejected.
Inkjet printing principle diagram
1 —Nozzle 2 — Modulator 3 —High-pressure deflection plate 4 — Flow into the storage tank 5 — Drum
Inkjet printing not only requires high-precision nozzle technology, high-precision control technology, but also requires high-purity, high-concentration, high-fastness, and high-stability inks to match it to have use value.

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