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FLEXO Magazine : June 2013
For solvent and UV inks, the chamber is best situated where the anilox roll enters from the bottom side of the chamber as the web travels vertically. While the ink simultaneously squeezes the air out of the cells. With water-based inks or coating, the anilox enters from the top into the ink chamber, because foam is less likely. Air is present in the upper part of the chamber and thus escapes more easily from the cells. If the web travels downward, less time is available to remove the entrapped air in the anilox cells. Pressure of the ink or coating is maintained at a constant rate. The operator raises the pressure, so that a wall of ink is created at the point where the rotating cells meet the blade. This prevents air-bubbles from entering, even when the press is working at full speed. A clamp allows the doctor blades to be slotted into position or released immediately, optimising changeover times. A range of chambered dual doctor blade systems is avail- able suiting different flexo printing and coating situations. • For paper, folding carton and film substrates, an ink volume of between 1.35l/m and 2.2l/m is advisable, suit- able for anilox diameters between 64 mm and 250 mm, web-widths up to 1,800 mm and printing speeds up to 500 m/min. • For label printing, a “closed cassette” variation is ideal, for situations where processes can be interchanged at each print station. Such a system may be capable of accommodating up to 800 mm anilox roller widths, and volume requirements as low as 0.2 liters. Thanks to the foam prevention characteristics of the cham- bered doctor blade, the flexo process is proving to be a reli- able, fast means of applying a coating layer at the final stage of an offset printing line. The coating station protects the offset print from being smudged without the need for an expensive drying operation, especially in the case of faster reel-to-reel situations. Chamber doctor blades for offset printing lines are designed to accommodate anilox roll widths of up to 1,600 mm width and speeds of up to 300 m/min. INK SUPPLY SYSTEMS An ink supply system, situated beside the printing press, circulates ink from ink bucket to anilox roller at a controlled viscosity, flow and pressure. Stable circulation keeps the ink at constant viscosity to ensure stable ink density on the printed substrate. Flow is measured by counting the pump strokes. The stroke volume of the pump is known and measured at an accuracy of +/- 2 .5 percent. Calculations in the software ensure that the FlexiPrint IMW Chamber Doctor Blade System E-Line, for water-, UV- and solvent-based inks and mid web flexo coating. 88 FLEXO JUnE 2013 www.flexography.org FTA’s 2013 Fall Conference & Tabletop Exhibit OctOber 14-16 | Kansas city, MO GOTDATA? NOWWHAT? Harness the Power of Your Data for Smarter Printing. Are you using the right methods of data collection (or none at all)? Do you have quality data, or is it trash-worthy? Do you know the easiest ways to analyze your data so that you can recognize trends, pinpoint areas in need of improvement, and quickly troubleshoot problems as they arise? With a virtual sea of data comes the challenge of making use of it. We’ll show you how. October 14-16 | Kansas City, MO Register today. www.flexography.org