Posts: 2
From:new zealand
Registered: Sep 2001

posted September 26, 2001 05:19 AM               

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HI dudes
Can u please help urgent!
we are running white ABS on a vented barrel and a 6inch screw at 35 rpm.
we are finding that we are venting material and the material is degrading to the point of browning. we have been told to run barrel temps at around 200^ to 220^ ??
but we are not having any luck

Can you please help
Thanks ..

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Posts: 386
From:Christchurch,New Zealand
Registered: Jun 2001

posted September 26, 2001 04:56 PM               

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Are you predrying the ABS at all?- I suspect the material residence time is too great at 35RPM. What melt temp are you getting with your settings?
We run ABS with barrel profile of 190-240C, 220 through adaptors/screencahanger and 210C across the die.

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Posts: 386
From:Christchurch,New Zealand
Registered: Jun 2001

posted September 28, 2001 10:47 PM               

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Are you adding regrind? the fact that regrind already has two or three "heat histories" plus the fact that because the surface area
to weight ratio of regrind is higher than pellets (of the same material), regrind absorbs heat faster and degrades sooner. And given its heat history, this could be giving the discolouration you describe.

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Posts: 146
From:Allentown, PA - USA
Registered: Jun 2001

posted October 10, 2001 02:17 PM            

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If you are "Venting" material, then eighter the screw is not designed for the material, or you have the temperature profile messed up or too much pressutre at the screens (Regrind or . . . ?)

Let us know . . .

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