An Update on 'That Vision Thing'
Way back in 2012, I wrote a blog about vision systems in the bindery. Well, it’s late 2016, and I’m feeling this needs a refresh. If I could name one technology that wasn’t around in finishing 30 years ago, but is now (in a big way), it would be machine vision.
Because digital print is essentially data-driven, there is both a need to verify that all of the intended print elements are there, and to follow the integrity and control process through the finishing chain. The ability to apply print quality control in the print process via vision inspection is huge. Many digital presses now include vision systems as part of the press package. These press systems inspect the printed sheet or web in real time to alert the operator of print defects.
On the finishing side, because digital print can include variable data on multiple printed elements, cameras or barcode readers are needed to verify the “match” of these pieces, and to report back to a database file that the pieces were processed successfully (or not).
Since high-speed digital print is mostly continuous web, barcodes, or printed cut marks are used by the web cutters for accurate web cutting and for sheet perforation units. The same sheet barcode may be used by the follow-on finisher, be it a saddle-stitcher or perfect binder. The barcode can tell the binder or stitcher how many sheets or signatures are in each book, and that they are in the correct order. They can tell the binder the thickness of each book block. In addition, barcodes can trigger additional devices such as stackers, perforation units, punches, or divert systems. And for perfect binders, a cover barcode can inform the three-knife trimmer of each book’s unique trim values.
When a match between multiple finished pieces such as covers, loyalty cards, or inserts is needed, cameras can instantly determine (at high speeds) that the finished piece has been properly assembled. Database files are updated on-the-fly. Most importantly, the camera will determine the absence of a component (such as a plastic card), and it’s proper alignment on the media.
There is no doubt that vision systems have become an integral and essential part of digital print and finishing. Without them, digital would simply not exist in its current form. And when planning your digital finishing system, you would be wise to to read up on the current state of vision systems and how they will be deployed in your operation.