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FLEXO Magazine : June 2014
Less Is More Lower Your Linescreen & Cell Volume for Better Anilox Performance John Rastetter and John Bingham I t sounds counterintuitive to consider lowering anilox linescreen to improve a roll’s performance. For years, anilox producers have been recommend- ing that printers increase the anilox linescreen to improve print reproduction. The thought is that by increasing the anilox linescreen, more support is giv- en to the printing plate, producing cleaner print. Increasing linescreen does insure that more cell walls contact the plate, but what it primarily does is reduce the percentage of cell volume that is transferred to the printing plate, creating a thinner ink film. A thinner ink film produces cleaner print. However, there are negative side effects to increased anilox linescreen: • Plugged cells • Scoring • Premature wear There is a better way to achieve the same or better end result with improved ink transfer consistency and better anilox durability: De- creasing anilox cell count and cell volume creates an anilox engraving that produces a thinner ink film, more consistent ink transfer and an engraving that is more durable. ANALYZING ANILOXES Today’s anilox technology utilizes fiber optic, multi beam thermal engraving technology. Instead of using a blend of gases, mirrors and tubes to produce a single laser beam, a crystal creates a short pulse length beam that is so powerful that a single beam is split into as many as four smaller ones. The splitting of the beam is what currently enables anilox cells to be “multi pulsed” or “multi cycled.” The end re- sult is a great deal of heat and energy directed into the cell of an anilox within a very short timeframe. The benefit of fiber optic technology is the ability to produce a wider range of linescreens—from 35 lpi all the way up to more than 2,000 lpi—increase cell depth and volume per linescreen, and have cell bot- toms that are flatter, shallower and smoother than a comparable CO2 engraving. New cell shapes like elongated and hourglass structures are also now available. The downside of this technology can be cell durability—resistance to scratching, scoring and premature wear. Older CO2 technology typically burned cells with a single pulse and at a pulse length that, by comparison, is much longer than fiber optic technology. CO 2 technology does not vaporize as much of the ceramic that is burned to form the cell and leaves a rim of melted Image 1: On the left is the elongated cell technology and the right the hourglass cell. Note the clean sharp cell formation created by fiber optic laser technology. 58 FLEXO | JUNE 2014 TECHNOLOGY & TECHNIQUES Anilox Roll, Doctor Blade, Ink Selection Guide