| next newest topic | next oldest topic |
| Author | Topic: air bubble in a rod |
|
john Member Posts: 1 |
posted August 27, 2005 11:42 AM
   
I got an air bubble problem with a .155 hdpe rod .the center of the rod always have bubbles.I try to dry the hdpe ,different barrel temperature ,hot or cold and different screw speed but nothing working.the extruder is a 2.5 inch with a new barrier screw ,no vent.the screen pack is 40-60-100. any suggestion? thanks IP: Logged |
|
Tom C Moderator Posts: 581 |
posted August 27, 2005 01:47 PM
John, What you have is a void, not a bubble. Plastic shrinks as it cools slowly. If you freeze the outside of the plastic extrusion very quickly it will take the shape of the extruded diameter. Since the molten center of the plastic extrusion continues to shrink as it cools slowly, it pulls a void in the center. A typical solution is to run a hotter (125-150F), longer cooling bath. Sometimes the problem is caused by directing very cold water at the extrusion right as it enters the bath. ------------------
Tom Cunningham
Extrusion Technical Services [This message has been edited by Tom C (edited August 27, 2005).] [This message has been edited by Tom C (edited August 27, 2005).] IP: Logged |
|
louis33 Senior Member Posts: 128 |
posted August 29, 2005 08:07 AM
And sometimes the problem is solved by using hot water. IP: Logged |
All times are ET (US) | next newest topic | next oldest topic |
  |
|
Contact Us | Feed Screw Designs
Powered by Infopop www.infopop.com © 2000
Ultimate Bulletin Board 5.45a
