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| Author | Topic: Compression Ratio |
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bighead Member Posts: 4 |
posted June 20, 2007 05:40 PM
  
Is there any reference information related to compression ratios of extrusion screws vs. compounds? Thanks IP: Logged |
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Tom C Moderator Posts: 861 |
posted June 20, 2007 10:22 PM
A natural compression ratio is something like 2:1 (Bulk specific volume:Melt specific volume). Slightly higher compression than that helps to assure proper pressure generation and melting rates. Generally those compounds which have poor feeding characteristics require high compression ratios. Deep feed section help to feed these types of resins, but at a conventional compression ratio of 2.5 to 3:1 the metering section would be too deep. Poorly feeding materials are nylons, PP, HMWPE, POM. Additionally some reclaim extruders use high compression ratios becasue the scrap is low density and does not feed well. Compression ratio somewhat becomes a moot point when using barrier screws. Barrier screws can be designed for proper feeding melting and pressure generating characteristics with geometry which is independent of other screw sections. Barrier screw are also much more stable and more versitile than conventional screws.
Tom Cunningham [This message has been edited by Tom C (edited June 20, 2007).] IP: Logged |
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bighead Member Posts: 4 |
posted June 21, 2007 09:21 AM
Thank you very much for the information IP: Logged |
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Steve H Moderator Posts: 406 |
posted June 23, 2007 08:26 PM
Hi Bighead Welcome to the single screw forum. Here's some links that you may finf useful: Extrusion Screws For TP Composites Why screws are designed the way they are Melt Extrusion:The Basic Process Steve ------------------ If at first you don't succeed, skydiving is not for you. IP: Logged |
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bighead Member Posts: 4 |
posted June 29, 2007 09:27 AM
Thank you Very helpful information IP: Logged |
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