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Author
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Topic: air entrapment in clear PVC
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josh
Member Posts: 1
From:MN USA
Registered: May 2003
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posted May 19, 2003 04:34 PM
  
Do you know anyone who deals with air entrapment in the winding process of
plastic film extrusion? We have a problem of air entrapment in our clear PVC
film and can not solve this problem.IP: Logged |
Steve H
Moderator Posts: 181
From:New Zealand
Registered: Jun 2001
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posted May 19, 2003 08:09 PM
What exactly is your problem Josh, maybe someone who is a member here can help.Steve H IP: Logged |
zabielski
Senior Member Posts: 149
From:McHenry, IL USA
Registered: Nov 2002
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posted May 20, 2003 07:04 AM
The air entrapment you describe sounds to me that it is due to inconsistant gauge (thickness) control.As the roll builds, you'll see small area's where you can see almost clearly to the core (if it iis a clear PVC). That is what you want it to do. So, from left to right or vice-versa. Find that area of air entrapment and measure the gauge. You'll be supprised at what you'll find. Take several readings by different people to validate the gauge mesurements. Now you'll understand why the air entrapment occurs. The problem is in die adjustments to contro gauge uniformly throughout the width (transverse direction fluctuations) can only be corrected by correct die adjustments. What is the thickness and line speed? IP: Logged |
Bob Cunningham
Senior Member Posts: 41
From:Amesbury, Mass
Registered: Nov 2002
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posted May 20, 2003 07:26 AM
How much technology do you have in the winder? I assume you can control layon force, winding tension, etc. pretty accurately? Do you use a surface winder, center/surface, center-driven winder, etc.? Also, tell us more about the film. What is the application? What thickness? What modulus? What type of cores do you use? Thickness variation can certainly be an issue, as zabielski said. (A general rule of thumb: When looking to fix a problem downstream, make sure everything upstream is working right first) -Bob Cunningham [This message has been edited by Bob Cunningham (edited May 20, 2003).] [This message has been edited by Bob Cunningham (edited May 20, 2003).] IP: Logged |
joshc
Member Posts: 1
From:Sauk Rapids, MN
Registered: May 2003
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posted May 20, 2003 03:22 PM
I am the orignal poster, now that I am registared I can explain my problem. We are runnig a clear PVC film in a cast film process. We are generally running guage of about .032"-.040". Because we run a cast film operation we are able to hold very tight tolerances. I do not believe the problem in a guaging problem because the air is in little bubbles all over the film. The film is flexible, but somewhat tacky. I have been told to run a lay on roller on our winding process, but this did not help. I thought it could be gases being released after the winding operation, so we chilled the plastic as cold as we possiby could, this did not help. We have tried slip agents or lubricants in our formulation, this did not make any difference. IP: Logged |
Steve H
Moderator Posts: 181
From:New Zealand
Registered: Jun 2001
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posted May 20, 2003 03:27 PM
Hi JoshCheck the adjustment of your Air Knife, if you haven't had it apart for awhile, give it a good clean. This could be a cause of your problem. Steve H IP: Logged |
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