Purpose: Material storage to supply the feed while the unwinder accelerates to line speed. To absorb and store material while the unwinder decelerates after the feed stops; storage requirement is based on speed and feed length-vs.-acceleration rate of the unwinder.

The amount of material stored is equal to the total slack length minus the straight line length. Storage is increased by greater depth not length. Rule of thumb: 2 to 3 times feed length in slack for best operation. Types of Slack Loops include Horizontal, Overhead and paddle.
 

If the material is straightened prior to the loop then the radius of the loop cannot be smaller than the Minimum Bend Radius for the heaviest material that will be run on that line.

Minimum Bend Radius (MBR) is the minimum radius that material can be bent into and still spring back flat. If material is bent beyond its MBR it will retain set and cancel the effect of straightening. MBR is based on material thickness and composition. Rule of thumb: MBR = 360 times material thickness for mild steel.

The loop must be supported into and out of the loop by cascade rolls at both ends. Without support the weight of the loop will induce set in the material as it's pulled out of the loop.

The depth of a loop determines the length required and the amount of material stored.
Additional loop length doesn't increase the amount of material storage. Only greater depth increases storage.
 

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