Web201.41d Web Extremes – Flexible v Stiff
***201.41d – Web Extremes – Flexible vs Stiff
06 Slides Duration 02.35 v 15.04.28
201.41d.01 – Title Slide
Welcome to Web-Handling. My name is Dave Roisum. In this fourth clip in a series we discuss how web modulus affects certain issues in web handling and converting.
201.41d.02 – What is modulus?
So what is modulus? The layman might think of low modulus products as having a large stretch. This is not quite true even though there tends to be a correlation. Rather, low modulus products have stretchiness. So instead how much something stretches, it is howeasily it stretches. More technically, it is the slope of the stress-strain curve at modest loads.
201.41d.03 – Modulus – Grading a Grayscale
We can measure modulus with a tensile tester. Like always, material properties vary on a continuum. The most flexible web products, certain nonwovens, are even stretchier than rubber. At the stiff end we have metals. There is more than a three order of magnitude difference between stretchy and stiff in the web-handling world.
Modulus affects nearly every web-handling behavior to one degree or another. Still, in the next two slides we will only highlight some of the most troublesome issues.
201.41d.04 – Modulus – Stretchy Issues
At the stretchy end, we have immense difficulties in holding geometrical tolerances for length, width and thickness. What this means as one example is that we can expect and even calculate the resulting length and width variations given tension control variations; if we know modulus and Poisson’s Ratio respectively.
In the winding world it is way too easy to get tightness, in fact, crushing tightness.
201.41d.05 – Modulus – Stiff Issues
At the stiff end, we can have immense difficulties in draw and path control.
Also, as should be anticipated, it is very difficult to get wound roll tightness; even when all the winder knobs are cranked to maximum.
201.41d.06 – Questions?
Thank you so very much for watching this module in my plant practical video clips. Stay tuned for more extremes of web handling.