Pressroom Hybrids

When applied to a printing press, the term “hybrid” can be slippery. It refers at times to newspaper lines outfitted for commercial work, or to offset machines carrying UV and conventional inks. But defined more broadly, the term offers a useful slant on an important trend: adoption of platforms that get as much of the job done in a single pass as possible.

These machines provide tools for differentiation, production flexibility and a sharper creative edge. For this report, we're looking at press types that exemplify three different kinds of hybridization: variable-cutoff webs, DI (direct imaging) platforms and dual-process presses.

On webs, the width of the print form is governed by the dimensions of the plate and blanket cylinders, while the circumference locks in the repeat length. Historically, one cylinder rotation equaled one cutoff for book, commercial and newspaper presses. If the circumference of the cylinder can't be changed, neither can the cutoff nor the resulting vertical dimension of what's being printed.

The forms industry has long enjoyed flexibility in cutoff lengths. When cutoffs can be manipulated by using cylinder assemblies of different circumferences in the same press, the options start to multiply. Adjusting repeat length to job layout cuts paper waste. And with fast changeovers from cutoff to cutoff, web production becomes attractive for short-run work typically printed sheetfed. Variable-cutoff webs can produce this work with the speed and economy of web output.

While “variable-cutoff” appears among sheetfed roll-to-sheet converters, with infinitely flexible infeed lengths, any sheetfed can shift its printing geometry simply by switching to a different sheet size. The inherent flexibility of sheetfed is the benchmark that web press makers are trying to hit with solutions for variable cutoffs.

Drent Goebel's leading presses for variable-repeat are the patented VSOP (variable sleeve offset printing) family, available in 20.5´´, 33.5´´, 44´´ and 49.2´´ cylinder widths with repeat lengths from 15´´ to 44.9´´. On VSOPs, polyurethane composite plate and blanket sleeves swap out to change repeat lengths. Other Drent Goebel blanket-to-blanket models use hard-cylinder inserts: cassettes containing the plate, blanket and impression cylinders are slid out and replaced by cassettes containing cylinders of another size.

Another approach—replaceable spacer sleeves that fit over the plate and blanket cylinder shafts—allows the Diamond 16 MAX-V web from Mitsubishi Lithographic Presses (MLP, in commercial operation in Japan since December 2005) to vary the circumference within a cutoff range of 21.5´´ to 24.6´´.

Muller Martini's half-web 20.5´´ Concepta is a 1,200-fpm traditional variable-cutoff press that uses interchangeable cassettes. The 1,500-fpm standard Alprinta, available in half-web and three-quarter-web (29.12´´) sizes, also uses hard-cylinder inserts.

Muller Martini also uses VOI (variable offset insert) technology on its 1,200-fpm Alprinta-V. Instead of cassette removal, cut-offs are changed by replacing lightweight, carbon-fiber plate and blanket cylinders—while the impression cylinder stays in the frame. Repeat lengths range from 14´´ to 28.33´´. Plate and blanket cylinders awaiting their turns can be kept at press-side on a storage stand.

Swapping sleeves and cylinders is faster and more economical than replacing entire cassettes, notes Andrew Fetherman, press division manager for Muller Martini USA, though more durable cassettes are a good idea in situations where a limited number of cutoffs are needed.

Mitsubishi's relatively light (about 40-lb.) spacer sleeves are replaced with the help of a boom lift and swivel arm. Sales director George Sanchez says MLP is finalizing the design of the spacer sleeve to incorporate a clamping device. This refinement will permit cutoff changes using flat plates and metal-backed blankets, paving the way for the launch of the press in North America.

Goss's FPS Flexible Printing System newspaper web, which will see its first U.S. installation at the Free Lance-Star in Fredericksburg, VA, also has the capability to change cut-offs, though the conversion process is lengthier and more involved.

In Drent Goebel's VSOP presses, a computer-controlled pneumatic system injects air between plate or blanket sleeves and the mandrel—a mounting shaft—permitting the sleeve to be slipped on or off. Removing the air seals the sleeve to the mandrel. Plate and blanket assemblies are driven by servomotors that automatically adjust speed to match cutoff lengths. An offline station permits standard offset plates to be mounted to the plate sleeve.

Muller Martini's VOI system, also servomotor-driven, recognizes a code on the cylinders and adjusts motor speed accordingly. Fetherman says the lightweight cylinders are more durable than sleeves and don't need replacement after reaching rated impressions.

With these methods, the web doesn't have to be broken for removal of hard-cylinder cassettes, nor re-webbed after—chores that could eat up the better part of a shift. Cutoffs on Drent's four-unit VSOP press could be done within 20 minutes, says Eric Short, a North American director. Using the boom, says Sanchez, two crew members can change all four units on the Diamond 16 MAX-V in about 12 minutes, while the third crew member adjusts the inline folder. Allowing another 10 to 12 minutes for coming back up to color and registration, the press can resume production 20 to 25 minutes after the changeover sequence begins. According to Muller Martini's Fetherman, individual VOI cylinders can be swapped in 20 to 30 seconds without tools or mechanical assistance.

A key impact on production economy for variable-cutoffs is reduction of paper squandered as trim waste. With variable-cutoff presses, says Sanchez, it's possible to “match the image size to the least amount of paper you can use, to maximize paper savings.”

Offset machines that expose plates from a stream of digital data sent to on-board laser imaging units were introduced in 1991 by Heidelberg, which launched the GTO-DI, driven by Presstek plate and imaging technology. Eventually 2,000 DI machines were placed. Last year, Heidelberg announced it would offer rebuilt QM DIs, but not new ones.

Technically dazzling, DIs are geared for a production sweet-spot that is a factor of run-length, color management and workflow. DI suppliers claim advantages over toner-based digital print in quality, ease of operation and flexibility in substrates and inks. In addition to its OEM role, Presstek now offers its own branded DI presses. Ryobi/xpedx, KBA, Kodak and Screen also have offerings. The largest direct imaging offset press is KBA's 74 Karat, a 20.5×29´´ four-up, 10,000-sph central impression cylinder platform with a cartridge-fed, keyless inking system and simultaneous metal plate imaging. For DI presses in smaller formats, the offerings are Kodak (DirectPress 5634 DI Digital Offset System); Screen (Truepress 344); Ryobi (3404 E-DI and X-DI); and, offering the most choices, Presstek (DirectPress models 5334 and 5634 DI, Presstek 34DI and the 52DI). Swiss web press manufacturer Wifag also has built a newspaper press with direct imaging capability.

KBA and Screen have each developed unique approaches to DI offset, while Presstek supplies the laser imaging systems for all other DI brands. Presstek product manager Tom Leibrandt says the appeal of his firm's DI presses lies in the combination of technologies: simultaneous thermal plate exposure made by a stable laser achieving stochastic imaging equivalent to 300-lpi resolution; four-color laydown without gripper transfer; waterless print to eliminate ink-water balance issues; and digitally controlled functions that allow even a less-skilled operator to obtain first-class results.

A shop wishing to install a direct-imaging offset press should have in-house prepress and the ability to RIP files to an imagesetter or CTP device. That's enough digital infrastructure, Leibrandt says, to make “plugging in a DI platform completely seamless—it's just another device hanging off the network.”

Tim Kirby, national sales manager of Ryobi products for xpedx, says that DI systems work especially well for non-traditional printing environments, segments to which Ryobi markets its 3404 E-DI and X-DI presses, which use Presstek imaging technology.

The KBA 74 Karat compresses 12 tons of printing iron into a fraction of the space that would be occupied by a conventional half-size, 4-color press. Inking and printing units are located on one side, while feeder and delivery are positioned together on the other. The double-size plate cylinders, the four Gravuflow short-train inking units and the two imaging units are arranged vertically to the side of the central triple-sized impression cylinder. The Gravuflow units consist of just two rollers—ink form and anilox—that maintain uniform coverage with the help of sensors that monitor the keyless metering.

A Brisque digital front end typically controls the flow of prepress data to the 74 Karat, which feeds Presstek's waterless PEARLdry plates from an automatic plate changer holding two banks of 20 plates each. KBA says that the 74 Karat exposes plates with any technically feasible screen ruling and resolution.

Screen's Truepress 344 is unique among the DI platforms in combining on-board digital plate imaging with traditional wet offset printing. Screen says that the multi-array laser diode imaging head in the 13.4×18.5´´ press exposes four processless thermal plates simultaneously in three minutes, making it possible to run a 500-sheet, single-sided job in less than 15 minutes at up to 7,000 sph. The press can be equipped with an IR dryer for fast-turnaround, two-sided jobs.

The touchscreen-controlled Truepress permits designating one plate—typically the black one—as replaceable for versioned printing with accurate registration and fit. Continuous monitoring of ink densities and dampening levels are among the features of an automatic quality-management system. The press also is compatible with Screen's Trueflow workflow, which accepts PDF and 1-bit TIFF input and supports JDF.

Presses that combine sheetfed offset with the flexo printing process have been firmly embraced. Placing flexo units before offset units creates a hybrid line capable of unique effects.

MAN Roland introduced its flexo-based InlineCoater 10 years ago. It now offers a double inline coating module used in applications such as cigarette packages with water-based gold and silver inks. Its Roland 700 Ultima is often used to convert inexpensive carton stock with intensive metallic effects using its “smart” branded coaters.

The flexo-capable Roland 700 and Roland 500 sheetfeds can both be hybridized with the smart chamber doctor blade anilox-based flexo units for depositing coatings before and after offset printing. A sample hybrid application on one of these presses could include laying down a metallic silver with the first flexo unit, printing over the silver in up to six colors of offset, adding a UV coating in the second unit, then curing.

Heidelberg uses the term “Duo presses” to describe its 29´´ and 40´´ Speedmaster CDs equipped with flexo units prior to the offset units. Duo was first introduced on the CD 102, followed in 2004 on the Speedmaster CD 74. Heidelberg's model code for a typical CD 74 Duo with flexo before and additional coating after the offset units is CD 74-2+LY-4+LX, which translates to: two offset units (2), followed by flexo (LY) special coating unit (for metallic coatings, etc.), then overprint with four other offset inks (4) and coated at the end (LX). A flexo-before-offset configuration makes it possible to run things like opaque white on metallic substrates (label paper or board) and transparent plastic materials, or gold, silver or other pigmented liquid inks or coatings overprinted inline with conventional or UV offset inks.

Three long (up to 16 units) Speedmaster Duos currently are producing in the U.S. Other options for hybrid inline applications on these presses are finishing processes such as cold-foil stamping, diecutting, slitting and perforating.

KBA offers detailed notes in a technical paper (available online) that it has built such presses for specialty applications. Komori's longest sheetfed press—a 100´ line at RCL/ColorDynamics, Allen, TX—includes flexo stub coating units on a 10-color hybrid UV convertible Lithrone LS 1040 perfector. The stub coaters are positioned after each set of five units, followed by IST UV and IR interstation curing and using Harris & Bruno coating systems. The custom-built press is the longest Komori has made, delivering cured sheets ready for finishing.

Read more on hybrids at www.graphicartsmonthly.com, us.heidelberg.com, manroland.com, kba-us.com, presstek.com, screenusa.com and mlpusa.com.