Printing & Design Tips: January 2010, Issue #102

Flatbed Inkjet Printers

Inkjet printers have been around for a long time. Over the past several years, however, the technology has come of age. Not only are large-format inkjet printers regularly available including augmented ink sets to improve color fidelity, but now these digital presses are expanding beyond the cut-sheet and small roll-fed format altogether.

Flatbed inkjet printers, such as the Inca, allow the service provider to print directly on metal, wood, plastic, and other rigid media. This eliminates the interim step of attaching the flexible output of a traditional roll-fed inkjet printer to a flat substrate. The printed product can therefore be used immediately.

With this new technology, digital print providers can more easily produce indoor and outdoor signage, point-of-purchase displays, trade show graphics, backlit signs, and banners. Some can even print on glass doors. In addition, the output is often cheaper than the same job would be if printed via the silkscreen process (which would have been the preferred option prior to the invention of the flatbed inkjet press). In addition, halftone screens for these inkjet presses can be much finer than those used for silkscreen.

Flatbed inkjet printers are often huge. The print area on the Inca, for instance, exceeds ten feet by five feet. In addition, substrates as thick as 2 inches can be imaged on this press.

Until now, inkjet presses provided either high resolution or quick output. Now, with inkjet print heads distributed across the entire width of the print bed, a balance has been reached between speed and quality. In addition, these presses can print in both directions (known as bidirectional printing). Flatbed inkjet presses can image over 2,600 square feet per hour at resolutions up to 600 dpi, from edge to edge of the print bed.

Color ink-sets have improved as well, and now include CMYK plus other colors (such as either light magenta and light cyan, or orange and violet or green) to extend the gamut of printable hues. In addition, some large-format printers allow you to lay down opaque white either as a base on which to print the CMYK inks (that is, to improve opacity) or just as an additional color. Also, various coatings can be applied over the printed inkjet product.

Even more exciting is the ability of flatbed inkjet presses to use UV inks, allowing immediate curing of the ink upon exposure to ultraviolet light. This facilitates the printing of intense colors and precise halftone dots on multiple and varied substrates in record time.

And as with all other digital processes, whether xerographic or inkjet, these new presses allow for endlessly variable output. In all cases, the creative art files can be altered to make each printed piece specifically target each individual recipient.

Web-Fed Inkjet Printers

Just as there are now both a flat-sheet (or small roll-fed) digital equivalent to the traditional offset press and a flat-bed digital equivalent like the Inca, there is also a larger roll-fed (or web) option to consider.

While the flat-bed inkjet press would be appropriate for signage and other large-format printing on rigid media, and the traditional flat-sheet and roll-fed inkjet press might be perfect for a small press run of a variable-data job, for longer jobs (and particularly for long jobs requiring variable data imaging), the larger web-fed inkjet press is ideal. (To understand this difference, consider how a web offset press is more appropriate than a sheetfed offset press for long static press runs. This is because web rolls are more economical than boxes of press sheets, webs run through the press at faster speeds than sheets, and webs can be printed on both sides at once.) More precisely, these large-format inkjet presses can run 30” web rolls at a speed of 400 or more feet per minute, depending on the press and the specific job being printed.

In much the same way as a web offset press feeds paper from huge rolls through consecutive inking units and then (in the case of heatset-web presses) through ovens, roll-fed inkjet presses deliver a continuous ribbon of paper across the inkjet imaging heads. At the delivery end of the press, this paper can then be cut into sheets or rewound onto rolls for later finishing operations.

As with both cut-sheet (and small-roll) inkjet presses, and flatbed inkjet presses, many web-fed inkjet presses can use UV inks. In these cases, the UV lamps can cure the wet ink film instantly, allowing for immediate finishing operations. This can shorten the production schedule dramatically. It can also allow printing on non-porous substrates such as plastic or film, which would not be appropriate for either traditional offset printing or non-UV inkjet printing. In addition, these UV inks are especially light fast. They allow for superior color saturation. They have good rub resistance, and they do not release volatile organic compounds (VOCs) into the atmosphere. Of course, for jobs printed on absorbent substrates, these web-fed inkjet presses can be reconfigured to use more traditional oil-based inks.

[Steven Waxman is a printing consultant. He teaches corporations how to save money buying printing, brokers printing services, and teaches prepress techniques. Steven has been in the printing industry for thirty-three years working as a writer, editor, print buyer, photographer, graphic designer, art director, and production manager.]