Offline UV Coating Systems Lay It On Thick at On Demand
By Patrick Henry
Published: March 7, 2008
Toner-based digital prints aren’t as thick-skinned as litho, flexo, or gravure sheets—that’s just the nature of the process. Prone to scratching and scuffing when ungently handled, toner prints often bear the scars of the rough ride they must take through the unforgiving everyday world of print consumption.
Feeding sheets taken straight from the digital press, an offline UV coating system can support not only that output but any other kind of printing that the shop happens to do.
But top the toner with a barrier of UV-curable clear coating, and toner prints can face their daily distribution odysseys without fear. When ultraviolet light energy irradiates a UV-sensitive coating, the sheet’s transformation from fragile and wet to hard and dry takes place at the speed of molecular physics. If the coating is formulated to impart a glossy finish, the sheet gets a shine on its armor, a pop in its color, and a significant addition to its value as a sellable printed piece.
Conventional presses can coat inline with towers reserved for UV laydown. Digital presses can’t do that, but there’s an alternative that yields the same durable, good-looking results with an extra dividend of productivity. Feeding sheets taken straight from the digital press, an offline UV coating system can support not only that output but any other kind of printing that the shop happens to do. Given that relatively few plants offer only one printing process, the across-the-board applicability of offline coating is obvious.
Capabilities vary, but all of the offline UV coating devices seen at On Demand are built for safe operation and consistent results in mixed production environments.
It certainly is plain to see at this year’s edition of On Demand, where six equipment suppliers are conducting live demonstrations of offline UV coating systems. Their capabilities vary, but all of the devices are built for safe operation and consistent results in mixed production environments. They’re also alike in their ability to turn out the kind of bright, colorful prints that get snaffled up in an instant as trade show collectibles—a definite indication of the marketing appeal that offline UV coating can add to digital output from toner-based equipment.
Following are capsule descriptions of the six systems on display. With one spot-capable exception, all are flood coaters designed to cover all or most of the surface of the printed sheet. Some can lay down other types of coating besides UV, although UV is the primary application in all of them. The systems are available for ordering and delivery now, according to booth personnel.
Duplo (booth 616) Ultra 145A and 205A ultraviolet document coaters. Being shown for the first time at On Demand, the 205A is the larger of two models offering numerous ease-of-use features including automated self-cleaning and job setup via touchscreen control. Safety provisions include a lamp housing hood that pops up when a jam is detected, distancing the hot UV lamp from the stuck sheet and thereby reducing the risk of fire. Two sensors—one that triggers an air blast to keep sheets from curling around the roller in the lamp housing, and a fail-safe that shuts the lamp off if the air blast doesn’t work—further assure safe operation. Both models can apply matte, gloss, and satin finishes, and both can be purged by pumping alcohol in an enclosed cleaning system. The 205A coats sheets up to 20.5" x 24"; 14.5" x 20" is the maximum sheet size for the 145A. Coating speed is 1,312 to 6,232 sph (sheets per hour), depending on stock thickness and size.
Kompac (booth 613) Kwik Finish. This device can perform flood, spot, and “spot not” coating, the latter being a technique that keeps coating out of a specified area of the sheet. Kwik Finish uses standard flexo plates for spot work, which can include, according to Kompac, the coating of microlines and individual halftone dots. Kwik Finish can deposit not only UV coatings but aqueous formulas, sheet primers, and Sapphire sheet treatment as well. (An optional IR [infrared] dryer is needed for aqueous.) Sheets up to 14" x 20" can be processed, with a maximum coatable area of 133/4" x 191/2" (allowing for gripper margin). The coater is delivered with an integrated feeder designed like that of a press for accurate sheet positioning when spot coating is being done. For quality, an “air bar” feature supports the sheet and protects the wet coating from marring as the sheet passes without contact through the machine to the lamps. For safety, vacuum suction holds the sheet flat as it passes under the lamp to prevent curling and fire hazards.
MGI (booth 659) UVarnish UV and IR coating system. This small-footprint machine uses flexo-type coating technology that gets an assist from a built-in IR dryer. MGI says that by increasing the temperature of the coating fluid with IR before exposure to UV, the “orange peel” effect—an unwanted surface texture arising from inconsistencies in the coating layer—can be avoided. Equipped with polished steel rollers, UVarnish can apply glossy and matte finishes to paper and plastic. Sheet formats from 5.5" x 11.4" to 14.2" x 20.5" can be accommodated; stock thickness range is 50-lb. cover to 180-lb. cover. It comes with an integrated, fully automatic sheet feeder, and an automatic stacker can be added as an option. Production throughput can be up to 2,400 14.2" x 20.5" sph. According to MGI, Xerox is offering UVarnish as a coating option for its iGen3 digital color production press. The coater also has been certified for use with HP Indigo 5000 series digital presses, says MGI.
FMA Inc. RSC-series offline coating system (xpedx, booth 1423, and Konica Minolta, booth 916). This device can be seen at the xpedx booth because xpedx is its national distributor and at the Konica Minolta booth because its integration of IR with UV resolves a toner-related coating issue for the digital press manufacturer. FMA’s coater uses a three-roller metering and application system with a plastic doctor blade that is superior, says FMA, to the squeegee-type roller cleaners that other offline coaters use. The coating section can be detached from the rest of the machine for shipment to FMA when repair or refurbishment is needed. The coater’s upgraded drive system uses, instead of a chain, a rubber drive belt that is said to eliminate markings that can arise from speed differentials between the chain and the gears in chain-driven systems. FMA claims another quality plus in the fact that its product is the only coater with rollers made of EPDM (ethylene-propylene-diene monomer) rubber—a firm-surfaced compound that smoothes the coating layer to eliminate orange peel. The machine’s built-in IR dryer helps Konica Minolta prints by softening their wax-based toner particles before the coating layer is exposed to UV. This, says FMA, heads off curing problems that could stem from the unique composition of the toner. The RSC coaters are available in models for 16", 20", 24", 32", and 36" sheet widths; throughput speeds up to 5,000 sph are said to be achievable with an optional auto-feeder.
Ultra Systems (booth 1574) i-series UV coaters. Sheathed in black metal, the i-series coaters are claimed by Ultra Systems to be the only offline coating devices featuring PLC (programmable logic controller) drivers and function controls: computerized subsystems for full self-diagnostics and “machine trending” (for example, hourly production status reports). Another distinctive feature, says Ultra Systems, is electronic lamp ballast—a power-management technology that permits the UV lamps to consume less electricity and last twice as long as lamps not supported by electronic ballasting. The devices use agitating pumps to optimize the performance of coating fluids and stainless-steel doctor blades to keep coating rollers residue-free. Touchscreen controls include a roller pressure indicator that is said to simplify the task of pressure setting during makeready. The i-series coater shown at On Demand can apply full-bleed coating to sheets from 51/2" x 81/2" to 211/2" x 26" at speeds up to 5,000 sph with optional integrated automatic feeding. The machines also will be shown at drupa and at Graph Expo later this year.
Prisco (booth 518) UV roller coating systems. Prisco (Printers' Service) delivered its first offline UV coater more than 15 years ago for a plastic printing application. It comes to On Demand representing a line of equipment that is designed, the company says, for easy, modular upgrades; low initial cost of entry and fast ROI; and precise control of all coating parameters in any digital or offset pressroom. Prisco also promises single-source support as the supplier of a broad line of UV coatings. The coaters are available in models for each of three maximum sheet sizes: 19" x 251/2", 30" x 30", and 40" x 40". Standard features include a closed-loop recirculating UV dispensing system; vacuum sheet hold-down throughout; precision adjustment of coating metering; digital variable-speed control; and numerous safety features. Manually-fed systems can be upgraded to fully automatic feeding and stacking for throughput up to 4,000 sph.