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 12x18-inch sheet into 2x3-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.
The CCD scanner on the Duplo machine translates the image position into numerics by reading a registration mark printed on each sheet. It uses this data to make minor on-the-fly adjustments automatically to the cutting, slitting and creasing positions. As the image position changes from sheet to sheet, the adjustments are calibrated automatically, ensuring that not only the finished document is to the exact physical dimension programmed, but that the image position is consistent from sheet to sheet. The Duplo DC-645 CCD scanner scans a document
with a barcode for job recall, and a registration mark
for image-shift compensation.
Duplo currently offers this technology on its Slitter/Cutter/Creaser product line and nearline SCC Bookletmaking systems. It’s standard on the DC-645 and on the Bookletmaker, but optional on the DC-615, which is a light production model similar to the DC-645. The technology is not offered with any other Duplo solutions today, and cannot be retrofitted to other Duplo machines.
Si Nguyen of Duplo states, “The image-shifting feature is one of the main reasons why our clients place their investment in Duplo. Customers that use the feature are hooked on it, as it ensures peace of mind that the finished product is consistent.” He also added, “Look for future Duplo Slitter/Cutter/Creaser models with improved speed and additional capabilities in 2010.”
OK, so it’s awesome, but there must be a drawback somewhere. I asked, and the only drawback is that productivity is decreased slightly, as it takes a split second longer to verify image registration from sheet to sheet. That makes sense. I guess given the potential savings on time and materials from reprints and quality issues, it’s worth the wait.
Now that I know about this image shifting problem, I’m curious to know what other finishing machine manufacturers are doing to address the problem. I guess you’ll have to watch my blog for the answer.
To learn more about the Duplo DC-645, DC-615 and nearline SCC Bookletmaking systems, please visit http://www.duplousa.com/