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Dots OK - Producing Film Positives and Proofs with Wide-format Inkjet Printers

(December 2002) posted on Mon Dec 02, 2002

Discover how RIP developers, inkjet-printer providers, and long-time suppliers to the screen industry work to make inkjet separating and proofing a reality.


By Sean O'Leary

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It's hard to imagine why anyone wouldn't want to use a wide-format inkjet printer to produce film separations in house, providing it could be done quickly, inexpensively, and without a loss of quality. Compared to outsourcing seps from a service bureau, in-house inkjet imagesetting represents reduced costs and improved turnaround. Even thermal imagesetters used in house can't provide a more economical alternative. Inkjet systems go one step further than thermal units by being able to double as full-color output devices for one-off and short-run production of color graphics. Furthermore, inkjet technology holds the promise of producing inexpensive color proofs from the same file that generated the separations.

Many industry suppliers have been attempting to develop inkjet imagesetting systems with just such capabilities during the past five years or so, but with spotty results. Now it appears that we are actually on the threshold of technology combinations that will allow a much broader range of screen printers to use standard, wide-format inkjets to expand their in-house filmmaking capabilities.

Background in brief

To see how we got here and where we might be going, let's briefly tour the misty depths of digital-printing history--specifically, the early 1990s. Yes, it was only a little more than a decade ago that wide-format digital-imaging equipment began to make inroads into short-run markets previously dominated by screen printers. Today, as throughput speeds increase with each new generation of inkjet printers, and flatbed inkjets expand digital capabilities into a broader substrate range, it is inevitable that digital methods will continue to make progress into screen-printing territory. What we can realistically anticipate is a process of gradual integration of digital-printing technology into screen printing (or vice versa) that will continue for the foreseeable future.

One of the assumptions among other graphics industries is that screen-printing technology itself has remained static, while allowing digital technology to chew up larger and larger pieces of the pie. This isn't true. Faced with new competitors who can turn jobs around more quickly, screen printers have responded by attacking a series of bottlenecks in prepress and by further reducing production costs. In fact, pure digital-printing companies continue to be amazed at how difficult it is to compete with screen printers in medium- to high-volume work. So if screen printers can continue to reduce prepress time while lowering production expenses, this printing technology will be viable for graphics applications for a long time to come.

Appropriately, digital technology has given screen printers the tools to remain competitive in the digital world. In the early stages of digitization, graphics software leveled the playing field for all forms of graphic arts. The next phase saw the replacement of conventional photographic-separation techniques with digital PostScript imagesetters that could quickly produce color separations directly from computer-graphics applications. Service bureaus equipped with wide-format imagesetters were able to turn around a color separation in a matter of a day or two, greatly reducing the time previously required by traditional film houses.

In 1994, the possibility of bringing digital separation methods in house emerged in the form of the Aspect imagesetting system from Autotype, a British company with US operations in Schaumburg, IL. Based on a 36-in.-wide thermal imagesetter and driven by a special version of the PosterMaker RIP software from Wasatch Computer Technology (Salt Lake City, UT), the Aspect system was the first effort at economical, in-house, digital color separating specifically for screen printing.

Today, possibly 1000 digital thermal imagesetters are installed around North America, including systems sold by both Autotype and Houston, TX-based Oyo Instruments. However, with price tags running up to $100,000 for a 54-in., large-format thermal system, this type of in-house capability is suitable primarily for larger shops with the resources and job volume to justify the expense.

The possibility of a similar solution that uses less expensive inkjet printers as output devices was also raised early in the game. Both vendors and users have tried an assortment of solutions with varying degrees of success. Perhaps the most viable products have evolved in the small-format garment-printing segment, which has lower resolution and accuracy requirements than graphics printers.

Using the Epson Stylus Color 3000, Stylus Color 1520, or similar inkjet printers as output devices, several vendors have developed RIPs capable of converting data from graphics applications into halftone dots for textile screen printing. Dot shape and size, screen angle, and line rulings are set in the graphic application and applied by the RIP. Products such as FastRIP from US Screen Printing Institute, Tempe, AZ, and Screenprint Separator from Squaredot, Seattle, WA are available in the $500-1000 range. Combined with a desktop inkjet (or laser printer), these specialty RIPs have allowed thousands of garment printers to set up in-house film capabilities for a total initial investment of less than $2000.

The one thing that has not yet emerged, however, is a mainstream, inkjet-based, film-output solution applicable to mid-sized and smaller graphics shops following business models that don't justify the expense of an imagesetter. But that's all changing now.

Inkjet seps today

Inkjet-produced film separations have evolved according to a pattern typical of technology that relies on several disparate components. In specialty-application areas, the potential user is subject to the decisions of product manufacturers with diverse backgrounds in different industries. Their primary objectives may not involve the particular niche under development, either because it isn't on their radar or because the base of installed users doesn't yet exist.

Inkjet separations and proofing for screen printing are classic examples. Bringing everything together not only required improvements in software, inkjet printers, and film media, but also someone to integrate and test the components as a system.

Software Until recently, most software RIPs were developed and marketed for print-for-pay environments and the digital production of full-color graphics. Several additional utilities needed to be built in to produce film separations on an inkjet printer. The most obvious is the ability to generate--and ideally, to control--halftone screens appropriate for screenmaking. However, other functions are also required for a RIP to perform well in a screen-printing prepress capacity.

"RIPs intended for driving image-setters must support workflows that are very different from those used for color printing," says Mike Ware, president of Wasatch Computer Technology. "When we began developing a RIP for the Aspect back in 1994, we quickly realized it was necessary to provide extra and distinct capabilities to support the monochrome output. Then, when we introduced inkjet as the output technology, we discovered a whole new set of challenges. Inkjets operate at lower resolutions and place dots with less precision than traditional imagesetters. There is no question that halftoning with inkjets is more demanding."

Earlier this year, the company released SoftRIP SP for Screen Printers, a print-management package that in-cludes a CD-ROM full of Wasatch Precision Rosette Screen plug-ins. Not only do these plug-and-play halftone patterns give screen printers hundreds of options (Figure 1) for adjusting screening to minimize moir


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