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March 14, 2007
Spiraling Tape Needed?
I got an email from a fellow web handler recently saying they were visiting a plant and had just spent the better part of an hour removing spiral-wound tape from many idler rollers on a thin film laminator that were used to prevent wrinkles.
This web handler knew the theory that spiral tape has no spreading effect, but wanted to know how to battle the strong local opinion that the tape spirals were required to prevent wrinkles.
My reply:
What can I say about helically wrapped tape on rollers? I’m not a fan and yes, Ron Swanson of 3M proved (and presented a paper at IWEB in 1997) that there is NO SPREADING from spiral tape.
So why is it popular? It there something more happening than the pleasing and mesmerizing optical illusion? I think ridged rollers, either ridges formed by the gap between spiral tape bands or the ridges of one tape banded stepped on top of another, can have a wrinkle disturbing or wrinkle dispersing benefit. If the unwrapped roller is prone to wrinkles from the combination of traction, misalignment, diameter variations, baggy web in long spans, or other wrinkle sources, then the spiral tape can help by turning a tendency to form one big creasing wrinkle into several smaller non-creasing wrinkles.
Do I like spiral tape or recommend it? No, but it may seem like the easiest way forward.
My preferred plan of attack is the same as the person who sent this question.
1. Remove the tape and see what's up.
2. Diagnose where the wrinkles are forming, starting with the first, most upstream wrinkle.
3. Look for the tale-tell signs of shear wrinkles caused by poor alignment (diagonal troughs and walking wrinkles).
4. Measure and maintain alignment.
5. If wrinkles persist in a few locations (rarely do all rollers have wrinkles), try using masking or similar tape to create a concave roller with a percent diameter variations appropriate to the web strain.
6. If concave rollers don't work, feel free to try your favorite spiral tape pattern.
7. If you want to eliminate all tape on rollers, which is a great idea for contamination-sensitive products and for an operator-independent process, there is more hard work ahead, but it can be done. This harder way forward includes work towards optimized traction (wrap, tension, and traction coefficient), optimized span lengths, reducing bagginess, and tactical use of concave rollers.
The best argument against tape is contamination. If tape is left on a roller long enough, eventually you see small pieces missing. Where did they go? Off to you customer and won’t they be happy!?
tjw
For an update on this story, check the comment below:
Posted by Tim Walker at March 14, 2007 11:58 AM
Comments
Update on removing spiral tape...What happened?
1. The visiting engineer convinced the plant to remove the spiral or helical tapes the entire coater.
2. The operators complained (with colorful language) about doing it, saying they couldn't run the machine without the tape.
3. Started the coated. No problem.
4. They've been running fine for over a week without them, still without a problem.
5. Science 1, optical illusions 0.
-tjw
Posted by: tim walker at March 20, 2007 05:52 AM
