Unique Press Design
The Presstek DI presses use Presstek’s Zero Transfer Printing (ZTP) process. With ZTP all four colors are laid down onto the sheet without any sheet transfer between colors. ZTP provides:
» First sheet register
» Precise registration, sheet-to-sheet, job-to-job
» Sellable color within 20 sheets
» Excellent ink coverage and reduced waste
A satellite V-shaped 5-cylinder system consists of two sets of double-diameter blanket cylinders and plate cylinders which rotate around a triple diameter impression cylinder. Each sheet is tightly held by the impression cylinder grippers and rotated twice without being transferred for precise four-color printing. The large diameter of the impression cylinder reduces paper curling as well as damage to the substrate.
A. Presstek DI presses use waterless offset inks. The ink train has four form rollers; three chilled rollers cool ink, eliminating toning.
B. Ink keys are preset during ripping, based on color profiles and exposure area for each color in a specific job. Auto start-up pre-inks plates before sheets move through the press.
C. ProFire Digital Media inside each double plate cylinder is automatically dispensed; plates are then tensioned. The press declutches, freeing plate cylinders to spin at 300 rpm during imaging.
D. Presstek’s ProFire Excel imaging unit simultaneously images all four cylinders at 2540 dpi in 4.5 minutes.
E. ProFire Digital Media spools contain enough material for 28 (DirectPress and Presstek 34DI) or 45 (Presstek 52DI) full size printing jobs; used plates are automatically transferred to a take-up area.
F. Once imaging has been completed, a two-step automatic plate cleaning is initiated. A vacuum then removes any remaining debris from the plate.
G. The DI press features double-plate cylinders, with matching double blanket cylinders beneath. The bearer design assures consistent impression pressure. A V-shaped configuration radiates from a common impression cylinder.
H. The triple-sized common impression cylinder holds two sheets tightly, eliminating potential for misregistration because there is no gripper change. A sheet picks up four colors in two revolutions
I. Register board/push guide precisely shuttles stock to ensure accurate infeed. Proven feed systems accommodate a wide range of standard stocks, or even plastics, envelopes, Tyvec and other specialty stocks, in calipers from .0024"–0.02" (0.06–0.5 mm).
J. An infrared dryer expedites curing of waterless inks. An autoclean cycle prepares ink rollers, blanket, and plate cylinders for the next image. Total changeover takes about 10 minutes