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Digital Press Toner Enhancements
by Henry Freedman
Punch Graphix’s Xeikon 6000
At Graph Expo, Punch Graphix’s Xeikon 6000 stood tall—literally and figuratively. The webfed color digital press, its tall print tower housing paper festoon and print engines, features fiber-optic communications and enhanced RIP for increased speed vs. model 5000: It runs 160 5-color, 8½×11″ sheets per-minute on stock up to 350-gsm thick.
A new “FA” (form adapted) toner sharpens details, gives more vivid colors (CMYK colors are Pantone-licensed), improves lightfastness, smooths tones, and greatly extends the 6000’s color space when optional green, red, blue or orange toners run in the fifth unit. It can also carry new clear or white toners with security printing options. Color toner optimizer software advises on selecting which added toner to run, based on intended PMS match, greatly expanding the color space.
The 160-spm duplexed speed surpasses digital sheetfeds such as Xerox’s 110-ppm 4-color iGen3. Just as in offset, color digital web presses are faster than sheetfeds, with advantages in head-to-tail control of paper as it travelsthe press. Along with its handling and feed efficiencies, roll-paper costs less.
According to Xeikon, a new built-in color control system using an X-Rite densitometer holds color stable automatically. Xeikon also has an excellent printing cylinder register system for front-to-back and side-to-side register. Sensors measure paper and cylinder speed and printed images on the substrate, giving feedback to the controller for realtime adjustments and excellent register.
Impressive toner engineering
Ink’s role in offset parallels digital engine toner, which moves to a latent image placed on a photoreceptor, followed by image transfer to the substrate. In digital, the toner is then fused or affixed. With digital, the “how” of toned image transfer to the substrate is critical. The contours of Xeikon’s potato-shaped FA toner particles optimize the press’s 5-color process; their shape also reduces electrical power needs for fusing. (Rounded edges help toner transport from the bottles into the system bins and developing and toning stations. It also tends to lay down smoother without as much overlapping, thus less toner is used—and fused).
Xeikon’s clear toner for matte overprint also has security uses: it appears differently under certain lighting, and can’t be scanned—so fakes and originals can be separated. A white opaque toner for use as a first-down color on clear packaging, or offcolor substrates, can be followed with CMYK toners laid on top. The FA Toner is U.S. FDA-approved for food contact and food packaging.
Xeikon has also engineered an extra magenta, increasing gamut in the blue-violet area to behave and appear like the toner on the iGen3. “This is because more and more, we find that our presses show up in places where iGen3s are already installed, and people want to have the possibility to do load-balancing and reproduce the same jobs also on our machines,” says Dr. Lode Deprez, VP of Punch Graphix Toner & Developer Group. “The extra magenta has benefits in obtaining the highest lightfastness possible [e.g. for outdoor and packaging applications], and having a magenta that is dry food contact, FDA-approved.”
Notably, a lot of work has gone into producing spherical chemical toners where the particles line up like BBs, as in the Xerox DC250, for example. But application of these spherical toners to faster production digital presses hasn’t happened because of their behavior in carrying charges, among other reasons.