Run-ahead is a problem that occurs on printing presses where the paper rolls are braked by metallic bands applied to their periphery. Run-ahead occurs when the web in contact with the band decelerates faster than the roll, or when the web stops completely but the roll continues to rotate. This leads to a bubble, or bunching of paper layers, on the ingoing side of the bands. This breaks the web. A model has been developed to characterize run-ahead that takes into account press operating conditions, as wel as paper and roll properties.
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