Poor Roll Geometry
Idler rolls that are not cylindrical in shape will cause the web
to naturally turn if the roll is bigger on one side than the other.
A roll with poor geometry will skew the web and then the next roll
will attempt to correct its own entry angle by trying to turn the
web back the other way. This usually results in a wrinkle.
Poor roll geometry can come from poor craftsmanship in the manufacturing
of the roll, from excessive surface wear, or from inadequate design
specifications leading to roll failure or diminished performance.
Even poorly wound parent rolls represent a type of cylindrical
geometry on the line that can cause web-handling problems. Excessive
parent roll run-out or taper can translate into vibration and web
flutter. In other words, the condition of the material itself, as
a poorly wound parent roll, can end up creating wrinkles through
the whole process. If poorly wound rolls can't be avoided, a good
tension dancer system can help adjust for much of the web tension
variance coming off the parent roll.
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