Continuous Inkjet (CIJ) printers represent one of the oldest and most mature Inkjet technologies that can fire ink drops at a very high speed, sending streams of liquid onto paper, cardboard and a range of other materials. This printing technology is most suitable for large scale printing such as coding and packaging of products.
Operation of CIJ Printers:
Like laser, CIJ printing is a non-impact process. The operation of CIJ printers is easy to visualize — Liquid ink in various colors is squirted onto paper or other substrates such as plastic film and canvas to build an image. A print head scans the page in horizontal strips using the printer’s motor assembly to move it from left to right, and then back again while the substrate rolled up in vertical steps. A strip of the image is printed and the substrate moves on. To speed things up, the print head prints vertical row pixels at a time.
Most CIJ printers take half of a second to print strips across a page. On a typical A4 size paper, the print head operates at 300 dpi depositing at least 2,475 dots across the page. This translates into an average response time of about 1/5000 of a second. However, in future, technological advancement will allow larger print heads with more nozzles to fire at faster frequencies, delivering native resolutions of up to 1400 dpi and print speeds approaching those of current color laser printer.
There are different types of printing technologies used in CIJ printers. However, the three most common of them are thermal technology, Piezo electric technology and color perception.
Most CIJ printers use thermal technology whereby heat is used to fire ink onto the paper. The squirt is initiated by heating the ink to create a bubble until the pressure forces it to burst and hit the paper. The bubble then collapses and vacuum draws ink from the reservoirs to replace the ink that was ejected by the printer.
Tiny heating elements are used to eject ink droplets from the print head’s nozzles. Most thermal Inkjets have print heads containing 400 nozzles, each about the diameter of a human hair. These nozzles deliver ink drop volumes of around 8 to 1 picoliters (a trillionth of a liter), and dot sizes of between 50 and 60 microns in diameter.
There are several advantages of this method. The process permits greater control over the shape and size of the released ink droplet. The minuscule fluctuations in the crystal allow smaller ink drops and higher nozzle density. Unlike thermal technology, the ink does not need to be heated and cooled off between each cycle. This saves time and the ink in the printer is enhanced for its absorption properties and for withstanding high temperature.
Visible light falls between 380 Nm (nano meter) and 780 Nm on the electromagnetic spectrum. White light comprises equal proportions of all visible wavelengths, and when this light is reflected through an object, some wavelengths are absorbed while others are reflected or transmitted. It is the reflected or transmitted light that gives the object its perceived color. For example, leaves are usually seen as green because chlorophyll absorbs light at the blue and red ends of the spectrum and reflect the green part in the middle. CIJ printing operation is based on this principle for creating relevant color wavelengths on products.
These three advanced technologies involved in Continuous Inkjet printing process makes it the most popular choice in the printing industry across the world. In fact, it is so popular that it is now being explored as an alternative to lithography, etching and vapor disposition, too.