Opting for CTP

Implementing CTP may be viewed as a technological journey whose length and destination depend on your operation's starting point.

by Terri McConnell

Since its phenomenal debut at DRUPA in 1995, computer-to-plate (CTP) technology has been integrated into the daily routines of printers across nearly every commercial and packaging application. Why? Because the benefits of imaging directly to the printing plate surface from digital data are irrefutable. Digitally imaged plates carry sharper dots and are capable of delivering a wider color gamut. They register better on press. They are free of pinholes and the effects of light diffusion associated with analog film-based plate production. CTP has raised quality levels, reduced turnaround cycles, shortened press make-ready times, and minimized start-up material waste.

These results have been proven for newer direct-to-flexo plate systems as well as for the more mature offset systems. According to Carolyn Miller, a print buyer advocate for DuPont Cyrel, CTP for flexo is having a profound effect for consumer product manufacturers.

Though capital investment for a CTP system can top the million-dollar mark, pay-backs as short as 12 months have been reported. Agfa has recently completed a CTP productivity audit showing printers using digital plates are saving 20 percent to 30 percent on makeready within the first months of implementation, and as much as 50 percent when they are fully competent with the technology.

At Scitex's traveling CTP seminar, Andrew Tribute of Seybold Publications presented survey data showing 33 percent of potential CTP buyers were planning purchases by the year 2000. Some will buy CTP for cost-savings. Others will buy to maintain their leading-edge image. Still more will buy just to stay on par with their competition. Some will buy due to increasing pressure from print-buying customers. Whatever the reason, it's no longer a question of whether to use CTP—it's a matter of when and which technology.

Moving-target technology

There are literally dozens of approaches to computerized platemaking. For offset, a debate rages between thermal systems and visible light systems. Thermal technology features plate materials sensitive to heat rather than light, and which can be operated in daylight conditions. The laser must deliver a "threshold" energy level to the plate in order to expose a latent image. Due to this "threshold principle," the images on the plate are an exact replica of the energy delivered—and do not allow for "spreading" or render "unsharp" edges.

Creo, headquartered in British Columbia, recently celebrated its 1,000th Trendsetter thermal system installation. Allied with Heidelberg to sell and service throughout the world, Creo has pioneered a unique imaging head that exposes a square-shaped spot. This "Squarespot" technology creates halftone dots which reportedly exhibit no gain from the platemaking process.

There are dozens of thermal plate materials on the market, the most widely used being Kodak Polychrome—but there are alternatives. Printing Developments, Inc. manufactures bi-metal printing plates that feature copper-over-aluminum construction. The company says its Prisma CTP plate is gaining popularity in packaging applications due to its durability—the ability to deliver long runs while withstanding harsh substrates (such as carton board) and aggressive UV and EB inks.

While thermal technology is clearly entrenched, Sheila Nysko, Agfa's packaging segment manager, estimates Agfa's visible light platesetters are currently outselling its thermal units two to one in packaging applications. Visible light systems are faster (30 percent to 100 percent), and may require fewer processing steps than thermal systems, depending on whether the plates require baking.

"Thermal and visible light systems each have their benefits, and we'll help printers or trade shop owners do an in-depth investment analysis on both systems when they're ready to make an investment," says Nysko, who adds,"It's then up to the client to decide which method and approach is best for his business."

Nysko goes on to say that the CTP debate isn't likely to end with these two candidates. "Now that the technology has been proven and accepted, we're exploring ways to economically optimize the process." Agfa is investigating alternative imaging technologies. For example—Violet technology, which exploits a different materialto achieve the same quality as available platesetters but less expensively—or even ablative and processor-less systems.

When and how to make the move

Not only are there many platesetters and plate materials from which to choose, but printers can also select from several implementation methods.

"First and foremost, printers who want to produce digitally imaged plates in-house should already have an established digital infrastructure," recommends Nysko. "Installing a CTP system should be the last step in implementing a digital workflow." Before taking that final step, Nysko recommends these prerequisites

A minimum of one year PostScript prepress experience that includes trapping, stepping, and creating dot-gain compensation procedures

Six months experience with digital proofing for both contract and step-and-repeat approval

A high-quality analog platemaking operation with a 5 percent or less re-make rate

Sufficient plate consumption to justify the capital expense of a CTP system Printers not yet ready for primetime platemaking can partner with digitally equipped tradeshops. Keith Buisse, V.P. of Valley Engraving in Green Bay, says his company supplies both offset and flexo packaging printers. "In the offset world, we send single files to printers with computer-to-plate systems on-site. In the flexo world, we are investigating purchasing the device ourselves."

Buisse says he recently completed live comparison tests for a narrow-web flexo label printer that confirmed better results with digital plates. His company built the test jobs, and incorporated the printer's dot gain compensation curves. Banta Digital of Menasha, WI, imaged the plates on a Thermoflex device. "With the digital plates there was less gain than with conventional plates," says Buisse. "As a result, we held smaller percentages in the vignettes and were able to successfully match an item printed offset."

Some tradeshops install and manage a complete CTP workflow at printers' plants. This facilities-management approach allows printers to maximize benefits of CTP without having to make the investment in equipment and training. The number of tradeshops offering facilities-management services is growing steadily as CTP becomes an industry standard.

Printers can incorporate the strategy as a long-term solution, or as an interim step on the way to developing their own in-house department.