On Print | Digital Printers for Real Converters
- Published: January 05, 2015, By Dr. Dene Taylor
Advances in technology now make it possible for you to handle the move to digital just like you did when bringing in flexo or gravure.
Two years ago I described what full width digital printing could do for the converting industry1.
Any application with patterns or text, printed by gravure or flexography, is a candidate for digital, probably for inkjet, but in some instances, toner-based methods.
Narrow printers, assembled by integrators, that could do interesting things for films and paper, and digital OEMS, such as EFI, CSAT, and Durst, had ultraviolet (UV) inkjet label printers already available. Plus, some narrow flexo and screen manufacturers, notably Stork (SPG) and OMET, had entered this same market. But manufacturers providing wide inkjet systems useful for converting had not.
The machines available back then were intended for graphic arts; they were too slow, and they did not complement converting processes. The wide gravure or flexo station had no equivalent.
Things have changed. Today, OEMs for conventional printing are supplying inkjet. Our most interesting example is wifag//polytype, which has recently started its inkjet pilot line. For a start, it looks like a pilot line with inkjet printing station, UV cure station, dryers by Pagendarm, and full size unwind/winder. Plus it is 700 mm (27.5 in.) wide and can run to 480 m/min.
The inkjet unit is capable of four-color process (CMYK) printing, but the Kyocera printheads are suitable for aqueous, solvent, and UV inks, so the line is not limited to graphics—it can run the same, or different but compatible, inks in each of the four positions.
Here, then, is a test bed from a respected industry vendor, designed for substrates we use, with the capability to support the range of applications we have. It can do everything on the list I made back in 2012, although some substrates might need separate pre-treatment.
Potential Converting Applications
- Any printing on any substrate—Prototypes, short runs, non-contact!
- Any type of pattern—Different coatings for thermoformed parts
- Patch coating
- Dosing or dispensing
- Short run process color printing
- Very costly materials—Silver pigment, pharmaceuticals
- Masks, resists
- Selective adhesion/release—Tamper evident films
- Very fast two-part coatings
- Variable thickness coatings—Casting plates, embossing masters
The Kyocera printheads on this pilot line have a native resolution of 600 dpi—that is 600 nozzles per in. of width. In graphic arts, inherent image quality is limited by down-web dot spacing, a combination of firing rate and web speed. For this line, the down-web spacing is 100 m/min (330 fpm). But image quality for industrial applications—ink type, ink thickness, edge quality—is very different.
For example, release coatings for tamper-evident structures can be a tenth the thickness of graphic black, so by using all four heads, some applications will be run at top speed. Similarly, thicker patch coatings, which have consistent densities and edges, can be produced by running slowly while still jetting at high speed, taking advantage of the fact that this line has a full featured drying section.
Hymmen is one of the leading machinery suppliers of presses and complete production lines for high-pressure laminates (brands such as WilsonArt and Formica), a great amount of which are patterned. Laminate patterns come from a gravure-printed paper that is saturated with melamine and cured at high temperature and pressure. Hymmen supplies the multi-station gravure presses, not just for paper, but for direct to panel as well. And it now supplies roll-to-roll inkjet printers up to 2.2 m wide with speeds up to 50 m/min, as well as panel printers up to 2.5 m wide, also up to 50 m/min.
What technical developments have changed the availability of inkjet printing? Firstly, components that used to be made by OEMs now can be purchased from specialist manufacturers. For example, operating software, system controllers, ink supplies, and wide printhead assemblies (print bars) that ensure precise registration. So for the OEMs of converting equipment, an inkjet printer installation has similarity to that for gravure. Instead of providing the framing for the gravure roll, doctor blade, and ink supply, they provide it for the inkjet printhead assemblies and the ink supply. And in place of having pattern produced by engraving, it comes from the print controller, RIP, and front end.
Polytype not only supplies inks for the primary product applications, it also makes them. (Polytype obtained Ilford’s skilled ink team.) This is a distinct advantage for the purchaser because one company is responsible for ink and machine, and so there is a major incentive to complete it all on time. However, the inks will come with OEM pricing. On the other hand, there are now hundreds of inkjet ink formulators, so those companies that have their own inks or depend upon a third party ink producer are not excluded—indeed their expert skills about these new applications should be welcomed.
There is another component to Polytype’s capability—aqueous inks for plain films. The best solution to produce flexible plastic packaging is aqueous inkjet that uses inks based on the ingredients of flexo or gravure inks. The food industry will have few issues to adopt this process.
Electrophotography (printing with toners) has broken into this market—HP Indigo 20000 at 30 in. wide and 85 fpm is an excellent system, but going faster or wider will be a real step change, and so far, toner has been approved only for dry foods.
UV inkjet is the process of choice for flexible plastic packaging based on image quality, speed, and width (500 fpm and 2.5 m, for example). Its component migration through film is a drawback for food, though. This problem is being addressed with low migration technology. I’m certain it will be successful, but the convertor must demonstrate compliance for every application, so it shall always have a burden. It would be much more attractive if individual compliance was not necessary.
So, if you are a converter and have thought about digital printing, now you can approach OEMs from our industry, buy the technology from them, and you could handle the process like you handled any other new printing process, just like you did when bringing in gravure or flexo.
Printing expert Dene Taylor, PhD, founded Specialty Papers & Films Inc. (SPF-Inc.), New Hope, PA, in 2000 for clients seeking consultation for technical management, new product design, development, commercialization, and distribution, as well as locating/managing outsourced manufacturing. Contact him at 215-862-9434; This email address is being protected from spambots. You need JavaScript enabled to view it.; www.spf-inc.com.
[1] Industrial Digital Printing for the Converting Industry, Dene Taylor & Vince Cahill, Presented at AIMCAL Fall Conference, 2012.
