The Unsupported
Web
You must have enough idlers to avoid long areas of unsupported
web. However, there is no special formula to tell you how many.
Too little support can result in bagging and wrinkling. Too many
idler rolls can result in unwanted drag and excessive tension.
Unsupported webs are also susceptible to other environmental factors,
such as the drafts of a nearby motor or normal plant ventilation.
We've seen examples in which an open door caused enough draft to
result in wrinkling. As so often is the case, the strength and weight
of the web will have a lot to do with the number and location of
idlers needed.
We encourage customers to send an elevation side view indicating
roller locations and where the wrinkling occurs. A Webex applications
engineer can use this to help troubleshoot your problem. If there's
a short span between rolls where it's wrinkling, we explore alignment
first. If there is a long span, we investigate support solutions
or additional idlers. When evaluating whether your span is short
or long, consider the width of the web. A tentative rule of thumb
is:
short = less than the width of your web
long = 3x the width of your web
|
