Maschinenfabrik WIFAG, a 92-year-old Swiss press maker, introduced two shaftless presses at NEXPO: the conventional-offset OF370 GTD and the keyless-offset OF570 GTD. Both feature gearless-transmission drives and flying plate-changing units, and the OF570 also features an ultra-short inking system.
Gearless-Transmission Drives
Unlike traditional presses, the new WIFAG presses do not have a central shaft to drive all of its units. Each printing nip has its own drive motor, as does each folder, RTF, nipping roller, infeed unit and driven roller. Optical readouts fed through fiber-optic cable replace the common driveshaft in synchronizing all the cylinders involved in a press run. The angular position of the cylinder is registered opto-electronically and processed in real time by computer.
Because each impression is driven individually, functions such as starting, plate changing, pre-inking, pre-dampening and washing blankets are totally independent. Each couple can be stopped, started and synchronized with extreme precision.
Plate-Changing Unit
The flying plate-changing unit permits plate changes for any reason such as zoning or edition changes. This can be accomplished without stopping the press. For example, if you have a four-high tower unit and need to use only the top two levels for printing a zoned edition, the bottom two levels could be plated for the next zoned edition. The web would travel through all four levels, but only the top two levels would print.
When the current edition was almost completed on the top two levels, the bottom cylinders would be brought up to speed. At precisely the right moment, the lower cylinders would engage and begin printing. At the same time the top cylinders would disengage and come to a standstill to plate-up for the next edition.
Plate-Changing Unit Plus
The PCU+ option allows changing the size of the product with minimal downtime. This is accomplished with a special autopaster that allows rolls of different widths to be switched over during production. For example, while a full roll is running, a half roll could be in the ready position. At the proper time, the half-roll paster would fire and its cylinders would engage and began printing.
Ultra Short Inking System
The OF 570 model features an ultra-short inking system that improves color printing, eliminates ghosting, has 60 percent fewer rollers than conventional designs and allows for page-by-page ink metering. It includes:
Frank Balentine is NAA's press manager. E-mail, balef@naa.org; phone, (703) 648-1217; fax, (703) 648-1216.
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