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  Solid HDPE Extrusion

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Author Topic:   Solid HDPE Extrusion
alanv
Senior Member

Posts: 13
From:UK
Registered: Apr 2005

posted July 06, 2005 12:28 PM     Click Here to See the Profile for alanv   Click Here to Email alanv     Edit/Delete Message   Reply w/Quote
I have ben asked if we can produce an 18.2mm solid HDPE tubular extrusion in a single pass. No special tolerances to be met, but not sure if a single pass is feasible. Any thoughts on this???

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Tom C
Moderator

Posts: 553
From:Brodheadsville, PA USA
Registered: Jun 2001

posted July 06, 2005 02:57 PM     Click Here to See the Profile for Tom C   Click Here to Email Tom C     Edit/Delete Message   Reply w/Quote
AlanV,

What problems would you expect? What does a double pass operation look like?

The normal problem with thick extrusions is a shrinkage void in the middle caused by rapid and extended cooling of the exterior wall.

------------------
Best Regards,

Tom Cunningham

Extrusion Technical Services

www.ExtrusionTechnicalServices.com

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alanv
Senior Member

Posts: 13
From:UK
Registered: Apr 2005

posted July 07, 2005 02:50 AM     Click Here to See the Profile for alanv   Click Here to Email alanv     Edit/Delete Message   Reply w/Quote
the double pass is a basic two stage build up, but we hope to run 4 or 5 continuous lengths of about 11,000 metres each. The problem being is the excessive time scale on double pass.

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Tom C
Moderator

Posts: 553
From:Brodheadsville, PA USA
Registered: Jun 2001

posted July 07, 2005 07:26 AM     Click Here to See the Profile for Tom C   Click Here to Email Tom C     Edit/Delete Message   Reply w/Quote
Alan,

Why won't it work in the single pass operation? I would think one of the requirements would be a grade of HDPE with sufficient viscosity to hold its shape outside of the extruder. Also you will need and extruder big enough keep the output velocity reasonably high.

------------------
Best Regards,

Tom Cunningham

Extrusion Technical Services

www.ExtrusionTechnicalServices.com

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louis33
Senior Member

Posts: 124
From:Allentown, PA - USA
Registered: Jun 2001

posted July 07, 2005 08:01 AM     Click Here to See the Profile for louis33     Edit/Delete Message   Reply w/Quote
I would thuink voids will be the biggest problem to overcome in a single pass, thus the need to double pass and build in layers.

You could of course run it into a coated pipe die where the pressure of the extrudate packs the material in and moves it forward as it cools. Still, your concern about line speeds and output of finished product per unit of time would limit your choices.

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alanv
Senior Member

Posts: 13
From:UK
Registered: Apr 2005

posted July 12, 2005 06:48 PM     Click Here to See the Profile for alanv   Click Here to Email alanv     Edit/Delete Message   Reply w/Quote
thanks for the advice folks, had to finish up doing a double pass. Lots of extra time, but good results.

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louis33
Senior Member

Posts: 124
From:Allentown, PA - USA
Registered: Jun 2001

posted July 13, 2005 12:13 PM     Click Here to See the Profile for louis33     Edit/Delete Message   Reply w/Quote
Glad to see that it worked out!

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