Web201.41e Web Extremes – Slippery vs Tacky
***201.41e – Web Extremes – Slippery vs Tacky
06 Slides Duration 02.46 v 15.04.29
201.41e.01 – Title Slide
Welcome to Web-Handling. My name is Dave Roisum. In this continuation of a series we discuss how the coefficient of friction affects certain issues in web handling and converting.
201.41e.02 – What is COF?
COF or Coefficient of Friction is not a material property. Rather, it is a property of two materials with flat surfaces. There is a static and a dynamic COF, but we will not discuss them here because their differences are minor. There are many instruments to measure these two COF’s.
COF has some pretty big effects in web-handling and winding. In fact, it is probably the single most neglected property. Still, there are a few who intentionally control COF by chemistry solely to improve web-handling, winding and converting.
201.41e.03 – COF – Grading a Grayscale
COF’s vary about an order of magnitude from slippery PET against itself to textiles and tissue against their selves. Most web-on-rollers COF’s are somewhere in the middle.
Beyond this we can get into true tackiness where no normal force is needed. Mild examples include merely wetting two smooth materials. Adhesives are more aggressive and hook-and-loop products are even more aggressive still.
201.41e.04 – COF – Slippery Issues
The biggest challenge with slippery materials in web-handling is the possible loss of traction on driven and undriven rollers. We covered this in great detail in module 3 of Web101 and we even have an AbbottApp to do the calculation.
In winding we tend to get loose type complaints such as out-of-round, loose cores and two of the six types of telescoping. This we covered in great detail in the winding modules of Web101.
201.41e.05 – COF – Grippy/Tacky Issues
On the other hand, we can have troubles if COF’s get too high, particularly when we have tackiness. In web handling, we can have troubles with roller release. In winding, we can get blocking and vibration. Curiously, we can get out-of-round complaints with high COF’s just as we did for low COF’s, but for different reasons and mechanisms.
201.41e.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.