Posts: 1
From:Istanbul, Marmara, Turkey
Registered: Feb 2005

posted February 19, 2005 01:49 PM               

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We are the pioneer producers of PVC door and window profiles in Turkey. It has been always a question for us whether the Parallel screw extruders or the Conical screw extruders are better. Can anyone make a detailed comparasion. Another question is that we worked with conical screw extruders until now but we bought 2 paralel extruders. What should be the operating parameters (mass temperature, pressure, etc.) for those two when compared with the conicals ?

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Posts: 82
From:Silver City, NM, USA
Registered: Jun 2001

posted February 21, 2005 10:52 AM               

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Such a comparison is similar to comparing Ford to Chevrolet----both work very well, and each has their proponents.
Conicals have larger,stronger helical gears in the rear,and since output rate is a function of the front diameter,for a given RPM a conical can accept more material in the feed zone.Of course alot depends on screw design.
Parallels may have to be run at a slightly higher RPM to acheive equal output rates to conicals, but costs of barrel/screw replacement are less.
Running conditions would be similar on the same PVC compound---typically a "reverse" temp. profile,hotter in the feed zone tapering down to the metering zone,with screw oil temp about equal to metering zone temp.Material at the vent should appear "cheesy",partially fused so a good vacuum can be pulled.Exit melt temp.normally should be in the 380-390F (195-200C).

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