Duplo Offers Patented Image-shift Detection System
Many of the technologies I’ll be focusing on in this blog will be brand new, but there are some technologies, like this week’s pick, that are worthy of mention even though they’ve been around a while.
This week’s technology is something that I learned about when I was researching an article about high-tech folding machines, called Folders: Wired for Success.
The problem of image shifting
Unlike a traditional offset printing press, digital toner presses do not have a gripper shaft. As many of us know, the gripper shaft control on sheetfed offset printing machines ensures that the printed sheets are transferred precisely and reliably from one cylinder to another. Digital toner presses rely on a transfer belt for registration due to their small available printing space and other mechanics that exclude the use of a gripper shaft. Other than the transfer belt and friction drive rollers, there is nothing that ensures the sheet won’t move vertically or horizontally during the printing process. This movement is called image shifting, and it can be a real challenge. For example:
If the operator programs a guillotine to cut a 12×18-inch sheet into 2×3-inch business cards, he’ll get exactly what he programmed the machine to do. However, if there is a 3mm vertical image shift problem on some of the sheets from the press, the paper cutter cannot compensate for this error as it doesn’t have a visual system to detect the mistake.
Duplo’s solution to this problem was to develop and patent an image-shift detecting system. First implemented in 2000 on its DC-545 finishing machine, the main function of the image-shift detection is to compare the printed position of the input sheet to the master sheet (usually the first sheet of the stack) that is read by a CCD scanner. The scanner also conveniently serves as a barcode reader to recall job memory settings. Now, if you’re like me and you don’t know what “CCD” means, it is a Charge-coupled Device and converts images into high-quality digital data signals.