TECHWATCH: tm: Speed Up for Digital Covers

Back in the old days, offset presses typically had to slow down when running heavier-weight cover stocks. This was due to feed, register, inking and other factors impacting operation. Today's modern offset presses auto-adjust and don't miss a rotation when printing on heavier stocks. Often point board thicknesses can run fast on offset presses, and printing cover stock at faster speeds has become routine in many shops.

Just as offset presses have grown to run thicker stocks faster, emerging digital press equipment is starting to accomplish this as well. Two new digital presses—the Kodak NexPress M700 and Xerox DocuColor 8000AP—are arriving on the street, touting increased printing speeds for cover stock up to 300 gsm. Both are dry-toner devices, and with limited space and the general purposes of this discussion, we will focus on these sheetfed digital press products.

The NexPress M700 and the DC8000AP have a design focus of printing digital color with dry toner on cover stocks without slowing down. The iGen3 has already mastered this and even prints on thicker plastic sheets. (In “Materials Ride a Magic Carpet,” GAM March 2005, p.45, we inserted 83,000 iGen3 electronically color printed thick plastic sheets into this magazine—a world record and a demonstration of what is possible.)

For the rest of the digital color sheetfed printing world, however, it is true to say that just as offset presses first ran slower with thicker stocks, so do digital presses. As one looks at mid-sized digital color press equipment, this has certainly been the case. The penalty for digital color has been huge. Cover stocks have virtually cut press speeds by 50% or more. And don't forget babysitting the feed and transport systems for “tricky substrates.”

All the basic requirements, like being able to feed, transport, register and deliver thicker substrates, must be met regardless of the printing process. In the case of digital dry toner-based color presses, the heat that melts and deforms toner to affix it to the substrate becomes a critical factor. We are now seeing great promise in engineering press fusers to compensate for many factors inherent in thicker and special substrates in both the DC8000AP and the NexPress M700. One key point: always look for good, wide-curving areas in the transport area so a digital press can be more forgiving with thicker stocks.

Thicker cover stock papers are heavier to pick up, need good separation on feeding and must be accurately registered. Thicker substrates hold heat longer and require cooling so sheets don't weld together (called bricking)—which is critical, especially with coated papers.

The NexPress M700 was designed for printing cover stock at full-rated speed, where the DocuColor 8000AP is an enhanced version of the proven technology in the DC8000 digital press that was developed (or engineered) to run cover stocks at full-rated speed. Xerox has the ability to field-upgrade the install base of DC8000s shipped after January of this year to AP models—tested to increase cover stock printing speed by as much as 100%. The DC8000 prints heavier cover stocks at 40 ppm, and now the new AP is rated at 80 ppm on 300-gsm stock.

The new Kodak machine prints 300-gsm cover stock at 70 ppm. NexPress toners lay flat and have an excellent look and feel from the color seen on the cover stocks. The M700 does not use fuser oil with the toner and has a wax component instead. This has many advantages, assisting in the fusing and postpress overcoating, while providing a nice, natural scuff abrasion resistance to the printed image. It also offers a greater degree of customer self-servicing with its Operator Replaceable Components, which include entire color imaging units.

This has advantages. Say you are printing a low-medium quality color folder for one customer and also have a job for a high-quality annual report cover for a very critical graphic designer customer.

Assume you are 50% into the monthly rated volume of your digital press. When it comes time for the high-quality annual report cover to be printed, you can put new components into the M700's CYMK imaging units. After you finish printing the annual report cover, you place these newer imaging unit components back on the shelf, saving them for the next time you have to print your most critical color, and replace with the imaging units removed earlier that have been used longer and have less life. This also allows the press operator to do a wide range of services without calling and waiting for a factory field service technician to arrive, which can be a make or break issue on a deadline job.

The NexPress system prints 4-color and images at 1200 dpi. Five feeders hold a total of 6,000 sheets, as does the delivery, consisting of a stacker and a proof tray.

The Xerox DocuColor 8000AP is based on a successful platform with an excellent printed image output, and has been the market leader in mid-level production color sheetfed printing volume. This mature press has had the field install adjustments over time and is now honed to be an industry production workhorse. The DC8000AP also excels at printing on specialty substrates—such as polyesters/synthetics, durable papers and ID cards/magnets—enabling a variety of print jobs to be produced. The ability to choose from no less than three RIP front ends and workflows makes the AP even more desirable. Xerox's field upgrade strategy shows the vendor is leveraging its technical and market strengths to enhance customer satisfaction and stave off market entry from emerging products like the M700, which is expected to be a formidable competitor.

The DC8000AP features 2400-dpi resolution and finishing options that include thermal binding, punching, stacking and bookletmaking. Its toner reservoir can produce up to 5,000 prints, while new cartridges are being loaded, and a new corotron cleaning assembly maintains image quality. The optional high-capacity feeder doubles sheet capacity to 8,000.

To view a video on the new DC8000AP click here.

Ask your vendors about thicker substrates they can print, and see how digital color cover printing is picking up speed. The DocuColor 8000AP and the NexPress M700 are worth close study if you want to digitally print cover stock. You will find new applications for these presses and some excellent printing quality on cover stock as a result of good engineering.