Posts: 6
From:quebec
Registered: Aug 2005

posted March 18, 2006 09:28 AM               

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i run LDPE on 2.5 extruder at 80 rpm .after the start up in the morning the output go down in the first two hours and does not move after that.I know on pvc , a little bit of cooling on the screw helps a lot but on ldpe ?It's a knew screw and barrel .I take the screw out two times and its clean.
Feed cooling is on.
barrel temp
zone1 350
zone2 365
zone3 385
zone4 385
die 385

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Posts: 4
From:Dover, OH USA
Registered: Nov 2005

posted March 20, 2006 12:05 PM            

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I've never ran anything but PVC so I may be way off here, but if everything else is the same, a hotter screw will have a higher throughput than a cooler screw. Vice versa for the barrel. Do you have zones in your screw as well?

Slip on the screw and stick to the barrel.

Did you introduce larger particle size regrind into the mix after making some the first two hours? That would slow your feed down.

Do you have screens in the machine? Maybe they need changed?

I don't know much about LDPE but the back end of the barrel seems hot enough to impact the feeding.

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Posts: 19
From:Penfield, NY, 14526, USA
Registered: Apr 2003

posted March 21, 2006 09:38 PM               

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John--
Try running the solids conveying zone #1 near the melting point of the LDPE, 260 F. The idea is to have the polymer just melting on the barrel to promote stick there, but not melting on the screw so it will slip there.

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Steve Derezinski
Extruder Tech, Inc.
585 248 9343

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