A small-diameter (typically G:H inch) steel rod used on some flexographic presses in place of a conventional impression cylinder. In some cases, the substrate to be printed is porous enough to allow significant strike-through of ink, which then can collect on the impression cylinder. Ink buildup can result in a variety of printing defects or in damage to the plate. The use of a stationary steel bar eliminates the problem of ink buildup since, as it does not rotate, the substrate is constantly wiping the bar clean. A flexo impression bar is also known as a tympan bar. (See Impression Cylinder and Flexography: Printing Unit.)
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