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Single Screw Control

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Topic: Single Screw Control

XtruDR
Member

Posts: 2
From:MN USA
Registered: Feb 2007

posted September 05, 2007 05:09 PM

Have been investigating ways to decrease output (dimensional) variation using closed-loop control for profile extrusion.

Primary material is rigid PVC, so melt pumps are not preferred.

Seems to be three approaches currently out there in industry:

1. Melt pressure (by RPM) and temperature control (per Holton Harris in "Extrusion Control").

2. Gravimetric control of either throughput (by RPM) or weight per length (by puller speed).

3. Dimensional control with laser or ultrasonic measurement (by puller speed for OD and RPM for x-sect. area).

Which is preferred when?

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Stephen J. Derezinski
Senior Member

Posts: 79
From:Penfield, NY, 14526, USA
Registered: Apr 2003

posted September 08, 2007 09:58 AM

It might be feasible to use a metering extruder (instead of melt pump) to provide the precise flow. A metering extruder has a screw of constant channel depth with the speed precisely controlled at a constant rpm. The pressure difference across the metering extruder is maintained by feed back controlling the speed of the plasticating extruder screw. Excellent flow control is possible.

------------------
Steve Derezinski, Ph.D.
Extruder Tech, Inc.
steve@extrudertech.com
www.extrudertech.com

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