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FLEXO Magazine : June 2011
Technologies & Techniques In order to form a more perfect seal, pressure must be maintained between the chamber and anilox roll during a pressrun. Under pressure, thinner blades flex, causing a wider contact area and edge slivering. See Figure 2 and Figure 3. Thicker blades (.008 in. / .010 in.) flex less than .006 in. • Pre-set angle as determined by the blade holder Ideal is 30 degrees – 35 degrees (Figure 4). STEEL vS. PLASTIC As discussed, a thin contact area will better meter ink and minimize the anilox ink film. Further, the rigidity of a .0 08 in. or .010 in. thick blade will resist flex better, resulting in less contact. In order to achieve the same rigidity value of steel, plastic blades must be three-to-five times thicker than steel. As a result, plastic blades have much greater contact areas, resulting in a much thicker anilox ink film. Simply said, plastic blades cannot meter as tightly as steel blades, making steel the better metering choice for all controlled ink transfer applications. Myth Buster...Some printers mistakenly think plastic blades are less likely to wear or dam- age an anilox roll’s surface and are safer to handle than steel blades. In addition to not meter- ing as precisely as steel, the edge of a plastic blade heats up and softens. Hard resin and hard pigment particles can lodge in the soft plastic edge (See Figure 5) and ride on the anilox roll’s surface. The hard particles can knock down cell walls. In addition, polymers from the blade can embed into the ceramic causing cell fill-in. These polymers can be very difficult to clean from an anilox roll. When it comes to safety con- cerns, used plastic blades can be just as cutting as steel and require the same safety precautions when handling. PERFORMANCE ENGINEERED Although plastic blades and composite blades are used for some printing with lower line counts, e .g . some types of corrugated boxes and laminating, steel is by far the most Figure 2: edge slivering. Figure 3: excess chamber-to-anilox roll pressure increases contact area and ink film. it produces edge slivering. Figure 4: ideal doctor blade set angle for Flexo. 44 FLeXO June 2011 www.flexography.org ELIMINATOR Introducing a New Standard of Label Metering Excellence • eliminates basic print defects including UV spitting • superior wear resistance • low friction against anilox • NEW AF TIP reduces break-in time • new alloyed material + dimension ...developed to meet the challenges of today’s high performance press room. R TM Printing Doctor Blades FLXON IS THE EXCLUSIVE DISTRIBUTOR IN CANADA - USA - MEXICO FOR +1.704.844-2434 www.flxon.com Performance Through Quality
Sustainable Spring 2011