Gravure Publication Presses
Publication presses are designed for high speed printing high quality color publications. Typical products include magazine, Sunday newspaper magazines, catalogs, newspaper inserts, and advertising printing.
The product requirements of publication gravure are:
• Multiple printed sheets must be folded and assembled into complete publications on the press, or delivered as folded signatures to the bindery.
• Variable cutotfs.
• High speed production.
• Versatile in-line finishing.
• Color consistency throughout the entire press.
• Adaptability to lower cost substrates.
• Lower start-up and running waste.
The overwhelming majority of U.S. publication gravure presses have either 8 or 10 print units. New gravure presses tend to be the 96 to 108-inch web width range; most other presses range in width from 70 to 92 inches. The same press can produce from one to six different products, with pagination of the signature from 8 to 128 pages.
Because of the width and speed of these presses, gravure publication plants use an enormous amount of paper. This requires sophisticated materials handling technology and a high degree of automation in loading paper rolls and splicing the new paper roll to the expiring roll when printing at high speed.
Characteristics of Publication Presses. Modern gravure publication presses are generally equipped with only one unwinder for eight printing units. The use of wide webs has led printers to run only one web per press, and larger diameter paper rolls, minimizing roll changeovers and related waste.
The roll of paper is transported, usually by automatic or motorized means, to the unwinder.
Publication press unwinders have automatic controls for roll changeover.
Web preconditioning units consist either of a hot air chamber or of heated drums, used to bring the paper to optimum temperature and moisture conditions before printing.
Reversible printing units are equipped with two doctor blade groups, to permit printingof a web that travels from left to right as well as of a web going from right to left. The doctor blade is typically locked in a doctor blade holder, which may be integral to the press.
Publication gravure presses often add a cloth-covered pre-wipe roller to the ink fountain to improve ink application to the print cylinder. On presses with variable cylinder sizes, the depth of cylinder immersion in the ink fountain is adjustable.
For wide web presses, the impression roller is equipped with deflection compensation, which applies force not only on the journal ends of the roller, but also in intermediate positions on the roller length, to provide pressure uniformly across the web. A printing unit for publication gravure press, with auto loading of print cylinder, is shown in Figure 4-2.
Electrostatic Assist systems facilitate transfer of ink from the cylinder engraving to the web. These systems charge the web, or the rubber, or the side of the impression roller, attracting ink electrostatically to the substrate.
Wide web presses are generally equipped with a rehumidifying system (steam bars) to raise the level of moisture in the paper when shrinkage occurs.
Publication gravure presses are connected to a wide variety of complex slitting, folding and finishing machines. These in-line operations include:
• Folding
• Stitching
• Auto stacking
• Inserting cards and couppons
• Gluing
• Perforating
• Flexo imprinting
• Letterpress imprinting
• Coating
• Trimming
• Rewinding
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