festoon

A festoon is a pair of sets of rollers arranged vertically or horizontally that holds a loop of moving web material (paper, film, fabric, or metal). The web enters the first roller set, makes a U-turn or S-curve around idler rollers in the middle, and exits through the second set. This configuration creates a temporary reservoir of slack material, typically several metres long depending on the festoon's physical size.

The core function is decoupling. When two sections of a web line run at different speeds, rates of acceleration change, or need independent timing, the festoon absorbs the mismatch. Material builds up on the roller sets when the downstream section moves slower, and deploys when the downstream section speeds up. Without a festoon, tension spikes would snap the web or force synchronisation that wastes product.

Festoons appear in printing presses between the print unit and the dryer, in coating lines between applicators and ovens, and in converting equipment before slitting or cutting stations. The rollers themselves are often rubber-covered to provide grip and avoid marking delicate surfaces. Idler rollers at the loop's turning points are typically smaller and may have bearing cartridges that allow free rotation under load.

The weight of the looped material creates baseline tension, but active festoons include pneumatic or spring-loaded arms that press the roller sets together. Dancer rollers, a variant that mounts on a moving carriage or arm, feedback tension signals to motor drives upstream and downstream, allowing real-time speed correction without manual intervention. This closed-loop control is essential for holding web thickness and surface quality within tolerance.

Common problems include web wrinkling if tension is too loose, or web breakage if it is too tight. Uneven roller wear leads to uneven tension across the web width. Roller sagging under heavy loads, particularly in nip points, distorts the web and creates tracking errors. Rubber degradation from heat, solvents, or UV exposure reduces grip and consistency.