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Mar 1, 2010 12:00 AM
Recently I have had the opportunity to work on a number of new presses that incorporate the latest technology for inspecting print defects, as well as some with automatic color control.
We have had web offset press color control for years. The first on the market was GMI (now owned by AVT), with its Color Quick system. This system, mounted in the web, would control color automatically +/- 0.06 D. At the time, that was just amazing. Today, there are numerous systems on the market for the web printer, and we have seen the acceptance of this technology.
In sheetfed, automatic color control units that read the sheet in the press are coming into the market. I tested one of these on a new installation, recently, and was extremely impressed. I observed a job running at 15,000 iph and holding color at 1.0 delta E, with a fairly new crew on a large-format press. On a half-size sheetfed, I watched a 4/4 run at 12,000 iph hold black at a delta E of 0.7, cyan and magenta at 1.0 and yellow at 0.4.
In my opinion, this is a technology that cannot be overlooked when considering the purchase of a four or more color press. A delta E of 1.0 is at the limit of variation the eye can see. One of the systems on the market gives you register control, as well, with the unit. Think of it this way: A good press operator can deliver virtually perfect color consistency with little or no effort.
Today we are seeing defect inspection units coming on the market that can spot the hickies or scratches our buyers do not want. Their value to you depends on your needs. I have seen a number of these in the field with mixed success. The key point is how small a defect you wish to see. A web inspection device that I saw working would detect to 0.010 inch and a sheetfed device to 0.026 inch. Now, you may say whether those numbers are fine or not. If you wish to tag large defects, then this might be something to consider. If you need to spot 0.002-inch small specks, then the technology might not be there for you. Most of the units will not see defects on metallic sheets. The highest resolution camera currently sold is 275 dpi, and it can compare the PDF file to the current sheet. This comparison is a great idea. It enables you to see small blanket smashes. Pharmaceutical and label printers have been the first to purchase such units.
Many of these systems on the market tag the bad sheet — I would question this practice from a productivity standpoint. Why tag bad sheets and then have to repile and sort loads by hand? That is an extensive amount of labor. Plus, tags fall out. To me, a better solution is to have a sorting delivery or double delivery on press. With this, you need no additional labor.
As with all technology, life does get better. Keep a careful eye on developments. Our customers are asking for more consistent quality.
Raymond J. Prince, NAPL partner consultant, is a leading expert in pressroom technical and operational issues. Contact him at (605) 941-1492 or firstname.lastname@example.org.