Posts: 1
From:N. Canton, Ohio USA
Registered: Aug 2003

posted August 14, 2003 11:10 AM               

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How do you figure the compession ratio of a 2.5 " 33:1 single screw extruder. I'm not clear on the formula. Do I take the barrel diameter in consideration, or just the measurement of root diameters? Is there a industry standard formula?

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Posts: 58
From:Nottingham, Notts., U.K.
Registered: Jun 2001

posted August 14, 2003 11:43 AM               

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The simplest definition of Compression Ratio is Depth of Feed Channel ÷ Depth of Metering Channel.

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Peter P.
pepe@polytech.co.uk
www.polytechconsultants.com

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Posts: 14
From:Canada
Registered: Jul 2001

posted August 14, 2003 03:46 PM               

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Possibly a better formula is the cross sectional area of the feed channel divided by the cross sectional area of the metering channel. This will account for flight pitch change. Compression ratio is not a good descriptor of feed screws because a shallow channeled screw and a deep channeled screw can have the same compression ratio but they would perform very differently.

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Posts: 230
From:New Zealand
Registered: Jun 2001

posted August 14, 2003 06:09 PM               

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Hi Eric

Welcome to the single screw forum

Felix is right, the Volumetric Compression Ratio is much more descriptive.

The measurements are based on the screw.

Steve H

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