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| Author | Topic: grilamid processing issues |
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paddy66 Member Posts: 3 |
posted February 02, 2007 07:40 PM
  
we are curently having a lot of difficulties processing grilamid L25 in a 3/4 inch extruder, unstable melt pressure,m/c amps erratic and inconsistant feed leading to tubing with unstable od, have tried various different screws,melt and throat temps, speeds etc without much success, any advice would be appreciated. IP: Logged |
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Steve H Moderator Posts: 401 |
posted February 03, 2007 12:24 AM
Welcome to the single screw forum. What LD is your extruder, screw geometery? are you running screen packs, what melt pressure are you getting. ------------------ If at first you don't succeed, skydiving is not for you. IP: Logged |
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paddy66 Member Posts: 3 |
posted February 06, 2007 06:06 PM
hey steve, extruder ld 24, various screws used e.g standard 3:1 metering, pebax mixer, low volume with deeper feed section than standard metering screw, generally up to 200 mesh used, melt pressure varies depending on tooling in head but generally 1500 to 3000 is ideal on this extruder,have ran other nylons sucessfully to a tight tolerance on this extruder cannot understand what the problem with grilamid is, thanks for your interest. IP: Logged |
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Tom C Moderator Posts: 834 |
posted February 08, 2007 09:26 AM
Sounds like a feeding issue. Try this; Set the first zone to as cold as possible and the throat water full on and let it stabilize for at least 4 hours. Turning the screw slowly, add the resin. See if you get a steady strong output. If not, slowly raise the first zone until you acheive steady output. Record the zone temperature that you get the highest amps draw. Start with the above procedure again with the extruder stopped and the first zone cold again for 4 hours. Start the extruder at the desired RPMs. Set the first zone to the above established temperature and wait for the first zone to heat up. The process should run well when the first zone temperature is acheived. You may find that after some period of time the process begins to become erratic. If this occurs, then you need screw cooling up to the end of the first zone. If none of this works, send me an email. ------------------ Tom Cunningham www.ExtrusionTechnicalServices.com IP: Logged |
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paddy66 Member Posts: 3 |
posted March 15, 2007 05:49 PM
Thanks for your suggestion, feed has improved slightly but still very erratic which is very puzzling as nylon 11 (vestamid) and grilamid compounded with a small percentage eva lubricant both run very well easily holding tolerance of +/- 0.02mm. I was wondering if there is any particular design of throat section or screw that is helpfull when processing this material, any thoughts you have would be appreciated. IP: Logged |
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Tom C Moderator Posts: 834 |
posted March 15, 2007 07:37 PM
I really don't know anything specific about this material. I'm just giving you basic extrusion troubleshooting tips. Melting point is 352F How do your amps look?
Oh yes, and what is the size of the pellets relative to the depth of the screw in the feed section? ------------------ Tom Cunningham [This message has been edited by Tom C (edited March 15, 2007).] IP: Logged |
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Stephen J. Derezinski Senior Member Posts: 64 |
posted March 23, 2007 08:38 AM
Feed hopper bridging, perhaps? Try a wide range of feed hopper levels. ------------------ IP: Logged |
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alpertl Senior Member Posts: 55 |
posted March 27, 2007 03:01 PM
quote: Try a low compression type screw, maybe 1.5:1 with a deep feed section, if you have one. IP: Logged |
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