Stationary Gauge Effect Occurring Randomly Across a Wound Film Roll

Q: I have an issue with a gauge band in my wound roll that causes a baggy lane in the film. The gauge band can occur anywhere across the roll, yet it doesn’t move across the web when the film is unwound. I have an oscillating nip and back-to-back winders. The gauge range is typically within ±10%. I have changed out shafts and increased my core thickness, but they make no difference.
What else can I try?
–Ohio film processor

A: Since you have a stationary gauge effect that occurs randomly across the wound roll, I would suggest you check the oscillation speed of your hauloff. The film buildup is greatest near the core. So a thick spot on the bubble accumulates as a high-gauge band at the core if the film is not randomized quickly enough. Since the film at the core is the foundation for the rest of the wound roll, that high-gauge band will stretch the film that builds on it, causing the baggy lane. Because the thick spot on the bubble is being randomized (albeit slowly) by the oscillating hauloff, it can create the gauge band anywhere across the core as a function of where the thick spot is at the time of cutover. Slowly increase the oscillation speed until the problem goes away.

–Bill Hellmuth, product group director, blown film
Gloucester Engineering Co., Inc., Gloucester, MA
(978) 282-9290 • gloucesterengineering.com