By Dr. Charles Bishop
From AIMCAL's Vacuum Web Coating Blog

I was discussing winding recently and was surprised to find out that web breaks were more common than I had thought. Web breaks had largely disappeared from my radar as over the years the tension and winding controls had been improved and the occurrence of web breaks had reduced to being infrequent.

So what has changed? Where before the web was being simply metallized and sent on now there are a significant number of vacuum processes that require multiple processing steps. This increase in handling has resulted in some rolls being damaged either by other processes not winding the web well or during transit. As for each process there is a loading and un-loading step where the roll has to have chucks fitted or removed. Between processes the roll is likely to be put into storage.

Thus if web breaks have become a frequent event it may be worth reviewing the whole manufacturing process including how the roll is handled throughout. Most web breaks occur through edge damage that starts a tear that spreads across the roll. This may be exacerbated by uneven tension and so poor quality web profile, or curved film, are more likely to be at risk of web breaks if handled poorly. When handling rolls it may be worth considering using temporary cheek plates to prevent accidental edge damage. This does not mean that using temporary cheek plates is an excuse to then not review how the rolls are lifted and located into storage racks and for operators not to be better trained in how much care is needed to preserve high quality edges.
www.aimcal.org

Wed Nov 19 16:35:00 CST 2008