What’s Your Game Plan?

Wear and tear

In compensating for ink leakage, an over-pressured doctor blade only solves one problem by creating another. When too much pressure is placed on an anilox roll, it causes scoring on its surface. “[Cosmetic score lines appear] on the anilox roller, but disappear after cleaning. [Severe score lines appear] on the surface, but are the result of actual damage to the cell walls,” explains Stamey. Scoring can be caused by unwanted particles from new anilox rolls, unkempt systems, or hard ink that becomes lodged between the roll and the doctor blade or mixed with the ink, he says. “Normally, these items individually would not cause scoring/anilox wear, but when mixed together, these particles form minute balls of very hard matter,” Stamey explains. “When doctor blades have been pressed against the anilox roller with excess pressure, the tip or edge of the blade bends and allows hard particles to be trapped between the anilox roller and the doctor blade. These particles stay trapped until they finally work their way out from under the blade. By this time, damage, either cosmetic or severe, may have already occurred.” And that damage becomes apparent on the substrate. Hard particles can damage cell walls and create grooves in the roll’s surface, which carry extra ink and can create streaks in the print area, says Foley. He recommends using steel blades with clean, “inclusion-free” structures and small, spherical carbides. “Poorly refined doctor blade steel is often laden with unwanted amounts of phosphorous, sulfur, and excessive carbon,” he says. “While the price may be attractive, the overall cost (of replacing or re-engraving an anilox roll) is eye-opening.”