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June 30, 2005
One-Sided Contact Web Handling
I continue to run into applications where one side of a web can't be touched. Sometimes one side is freshly coated, another time the web is easily scratched, and recently, the web had a big part attached to it sticking out one side. It's hard to go over a roller with a big bump on your web.
The first choice in one-side contact is to design your line like a scroll. Place the unwind in the center of one side of the scroll and your winder in the other side of the scroll. If your roll loading is cantilevered (rolls go in and out sideways), you can form a pretty tight sprially path around the unwind, as many times as are needed for your tension, guiding, and processing plan. When your done with your unwind spiral, move over to the winder side and spiral inward as needed until you hit the windup (or sheeting, the more likely finale to the bumpy product. All rollers will rotate the same clockwise or counterclockwise direction.
For tension control, you can still have 2 or more zones, but driven rollers will likely have 90 degrees of wrap (and of course no nips). A rubber roller can support a good tension change with 90 degrees, but a vacuum suction roller can do even better (again use rubber for high friction, if possible). Tension feedback will likely be with a transducer roller, since most people prefer 180 degrees on dancer rollers.
Other tricks?
If you need to go further or a more complicated path, an front side air turn can be used to reset you angle of orientation without contact.
For a more creative approach, turn the web on a 45 degree turn bar, sending the web of 90 degrees from the initial centerline or use two turn bars to shift the web laterally, much like changing lanes on the freeway.
Anyone who's seen me teach knows how creative you can be with air turns, web paths, and limited contact. If you haven't used air turns, don't be afraid of them. Many, many processes use them every day.
There are more tricks out there, some I discussed in my June 2003 article for PFFC "Can't Touch This (Web) - Part 3".
Posted by Tim Walker at June 30, 2005 03:16 PM
Comments
Vacuum Drum Roller or Hug Drum:
I am looking for a supplier who we can purchase a vacuum drum to handle film at 50decimeters/min. The drum needs to be stainless and will be used to measure footage.
Posted by: Marcel at May 15, 2007 01:42 PM
