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Customization of Inkjet Head Technology

(April 2012) posted on Tue Apr 03, 2012

The future for inkjet printhead development in terms of technology and business-management trends

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By Rick Mandel

Industrial printing
Large-format roll-to-roll and flat bed printing took off with the advancements of the piezo heads. The physical drop size of the Xaar 1001 heads are in the 6 to 42 picoliter range, which is more than visually acceptable within the event and POP categories that we now print. This head has a print swathe of 70.5 mm (approximately 2.8 inches), and fires at 5kHz. Therefore, this seems to position itself in the high resolution, less production market for UV or solvent inks. Whereas Xaar’s Electron head is focused in the wide-format indoor/outdoor market with a faster 6.5kHz firing, and a 70 pl drop size— more speed, larger drop, and specifies solvent ink only.
Chris Lynn, VP sales and marking of Xaar USA, expanded on the company’s perspective on inkjet printhead developments. Xaar believes that piezo has several inherent advantages over thermal inkjet for industrial strength imaging, she says. They believe the heads are more durable and have a longer MTBF (mean time before failure), with life times measured in years and not weeks. They can impart more energy to a drop of ink, so larger drops and longer throw-distances are possible. And they can handle a greater variety of ink types and viscosities, making for a more flexible machine, which can handle a greater range of substrates.
Lynn continued saying that the crucial developments in printhead technology in recent years have been greyscale (variable drop size) printheads, which Xaar calls XaarDOT, and the advent of side-shooter printheads in which the ink flows past each nozzle orifice (Xaar’s TF technology). The Xaar 1001 uses both of these technologies. The through-flow of ink across the back of the nozzles provides a number of benefits: easy printhead fill, increased reliability and self-recovery, minimal maintenance, and therefore reduced ink wastage through purging. In addition, the internal design of the printhead for TF Technology facilitates easy cleaning and color/fluid changeover. The ink recirculation design allows the print head to self-prime and self-recover from jet-outs, leading to the high reliability needed for single-pass printing. It also allows inks with high solids (whites and metallics, for example) to be printed in a single pass.
Greyscale printing gives the high resolution and smooth tones of a small-drop print head while providing the high productivity of a large-drop head. We have seen this optical illusion of variable dot size in the analog world of halftone printing. Many will remember second order stochastic dot patterns in color separations.
Lynn continued, “Xaar expects the market to continue to demand low-price, low-volume wide-format printers, as well as high-productivity machines with an attractive total cost of ownership.” The first category will be mainly thermal inkjet technology with water-based inks, and the second will be ever-faster piezo technology with UV-curable inks.
Konica Minolta’s view is their piezo inkjet heads are able to handle a wide range of inks to meet the requirements of various industrial applications. Their principle of “shear mode piezo actuation” with shared wall structure allows lower power consumption as well as a high-density nozzle array. On-demand dot size modulation, sometimes referred to as grey-scale mode, enables the printing of high quality images and functions to increase productivity. All the development work is based on advanced computer simulation techniques that can precisely predict the droplet formation process resulting from differential ink characteristics.
The KJ4A Series technology by Kyocera, is designed for UV inks and other inks with high viscosity. The unique technology powering Kyocera’s piezoelectric actuator enables 600dpi x 600dpi image quality with up to five levels of grayscale (visually 1,200dpi) by controlling drop size.
Variable Size Droplet Technology (VSDT) is the description of Epson’s Micro Piezo printhead technology to eject ink droplets of different sizes by varying the electrical charge given to the piezoelectric elements. This enables Epson’s printers to achieve variable sized ink droplets as small as 1.5 picoliters. The trend for greyscale/variable dot technology is also a mainstay for Epson.
FujiFilm’s recently released that the Dimatix heads also show diversity for applications. Variable drop sizes assist in simulating higher resolutions. Q Class Polaris of Dimatix heads has the ability to jet two colors simultaneously with picoliter drop size of 15 to 200.
“Polaris supports aqueous ink formulations in addition to UV-curable, and aggressive organic solvents, making it suitable for a growing range of commercial and industrial printing applications,” the company said. Dimatix has touted their variable dot technology with VersaDrop. The Spectra line has the VersaDrop technology and repairable advantages, while the Performa line is used in single-pass applications.
As an example of producing heads that advance specific industries, FujiFilm/Dimatix created the Inspira product for larger particle size applications, such as direct-to-screen devices, ceramic printing, and textiles. Samba technology also incorporates VersaDot with native 1200 dpi resolution for single-pass applications.
Inkjet head advancements are creating more opportunities within the industries that are more related to litho and flexo, in the manner that affected the screen process a number of years ago. These are the collateral, label industries, and electronic boards. As for wide-format printing, the thermal heads are pushing its way back
on the radar screen with the advent
of latex inks.


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