We recently encountered customer complaint regarding roll telescoping. Presently, we have the same tension settings for two different types of foil that have different roughness values. Would you recommend a higher or lower rewind tension for smoother foil surface (less roughness value)?
While roughness and COF often trend together, it does not necessarily follow that smoother surfaces are slipperier. Besides, COF is what matters. The exception is that at higher speeds (over a few hundred FPM), air entrainment is increased and the effective COF will decrease. Keep in mind that with some products (paper, film) it is possible/common to be able decouple smoothness and COF by chemistry.
In any case, let the winding roll tell you what is needed. If it does not telescope (or have other identifiable defect), no tension change need be made. If it telescopes, you must increase the starting tension and/or decreasing the tension at the finish (i.e., increase taper though I abhor the term for reasons I’ve written about on many occasions). These moves must be made until you either kill the telescope or that you run into some other limit of web (tension rarely can run outside of 10-25% of yield), wound roll defect, or machine limitation. This discussion presumes (and we all know what ASSUME stands for) that you have a Type 1 telescope. Unfortunately, people use the word ‘telescope’ for too many things. (Pictures would really help here). So, if you called a telescope the loss of roll edge quality at the top of the roll (at the latter stages of winding), then our strategy would be completely different: reverse taper.
I have attached an introduction to winding from my Web101 series that has a few slides on the common type of telescoping. You could also go to school where things like this can be better explained. I teach Web Handling and Winding in Chicago at the end of March.