Bending With The Punches

Pity the unsung punch. Compared to the star appeal of a shiny new press or high-speed finisher, the precise placement of holes into sheets of aluminum rarely gets a leading role. Yet many printers struggle with misregister caused by inaccurate punching.

At drupa, advances in punching were seen in the newest large-format platesetters—for example an 81´´ device—which can now simultaneously expose plates two- or three-up for smaller format presses. In some cases, variable punching is built in. As one example, the Kodak Magnus VLF platesetter can be equipped with internal punches that compensate for temperature-related plate expansion and contraction.

One hiccup in CTP punching: The accuracy of three-point register systems depends on perfectly trimmed plates. “CTP platesetters are very accurate, but there may still be registration problems when the shape of the plate is less than square,” says Stefan Kreitczick, managing director at BEIL Registersysteme. “With optical scanning, the distortions of the plate cut are eliminated.”

Plate punches and benders are increasingly equipped with optical registration systems, utilizing video cameras to detect and align cross-hair targets exposed onto the plate. These systems guarantee that the punch holes and plate bend are positioned in concert with the plate's image, rather than its edge. BEIL-America, based in Cincinnati, offers video registration on its automated high-line punches, with video or manual “magnifier adaptation” optical registration options on its more affordable easy-line and comfort-line punches.

“For commercial printers, most plate punching is now done within the CTP exposure unit,” notes Claus Alber, sales manager for German plate handling vendor 2B, which works with BEIl. “However, our customers that own a variety of different presses often find their platesetter cannot accommodate more than a few different punch systems.” To meet this need, 2B developed the Imagefinder multiformat punch/bender, with register-mark recognition as well as compatibility with their Tele-Service remote diagnostic system, Plate Organizer, Plate Tracking and Plate Quality Control System.

“The call for automation is everywhere,” says Katharina Gruber, NELA marketing manager. “Whatever the customer needs, we try to design it—from plate distribution systems to barcode readers and quality-control systems. We even offer a device to put slip sheets back onto the plates after they are developed and punched.”

NELA's Plate Quality Measurement (PQM) system provides a sophisticated analysis of image quality, compatible with both AM and FM screening workflows. Using two USB2.0 microscopes, PQM performs image analysis on tint screen areas as small as 5×5 mm. Data gathered from these images can be used to trigger a warning if a specific plate is out of tolerance, and all data is logged for quality-tracking purposes. Data is gathered from a small target that is imaged in the plate-bend area, providing feedback on the platemaker's exposure curve, laser power and focus, plus plate fogging and development.

OFS Group's Plate Quality Control System (PQCS.NET) is a multilingual application based on an SQL database that can be securely accessed over the Internet via a web browser. Alerts and warnings can be specified via the Client Notify Agent, with the ability to report statistics in XML format or as JDF data. OFS licenses this application for resale by several manufacturers, including Glunz & Jensen.

“By scanning 16 different patches within a compact 6×4 mm plate exposure target, we can assure consistent results,” says Al Brunner, VP sales for Glunz & Jensen. His firm has introduced the PlateLink Manager to centralize communication tasks across a variety of equipment sets, including G&J's plate loaders, CTP processors, punches and benders.

Another of the many plate punch vendors that hail from Germany, Berth Maschinenbau GmbH, calls its optical registration system “True Point Positioning.” This feature is available in Berth's OP equipment series, including the OP+ACM model that can precisely cut oversized plates into multiple smaller plates. NELA and Glunz & Jensen also offer plate shearing equipment that can split multi-up plates or provide a “clean-up trim” to ensure plate edge squareness.

ONLINE: Reach the author at hal@halhinderliter.com