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News Release from: Spirex Plasticating Systems and Solutions | Subject: Barr ET and VBET screws
Edited by the Engineeringtalk Editorial
Team on 29 September 2003
Screws aid efficient injection moulding
Spirex Corp has signed an exclusive agreement to manufacture and market the Barr Energy Transfer screw and the Barr Variable Barrier Energy Transfer screw to the injection moulding industry.
Spirex Corp has signed an exclusive agreement with Robert Barr to manufacture and market the Barr Energy Transfer (ET) screw, and the Barr Variable Barrier Energy Transfer (VBET) screw to the injection moulding industry According to Paul T Colby, President of Spirex: " Adding the Barr ET screw and Barr VBET screw to Spirex's comprehensive screw line brings our customers even more options in maximising production rates at lower temperatures and minimising wear while consuming less energy"
This article was originally published on Engineeringtalk on 9 May 2003 at 8.00am (UK)
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The Barr ET screw (US Patent No 4,405,239), features a patented low shear mixing geometry in the metering section.
Approximately 70 to 80% of the polymer is melted by the high shear, and the remaining solid is melted in the ET section.
Using the natural drag force of screw rotation, the remaining pellets are continuously mixed with the hot melt.
The mixing is achieved by low shear without developing undesirable shear or pressure.
The remaining pellets melt by the heat conducted from the hot melt by "conduction melting mechanism".
This allows a much lower melt temperature and higher energy efficiency.
Another advantage of the ET screw is better cooling.
The ET geometry gives better heat transfer from the melt to the barrel since the entire hot melt is continuously exposed to the barrel as a thin film while the melt flows from one subchannel to another.
The Barr VBET screw (US Patent No 6,599,004) features a unique patented geometry which significantly increases conductive melting and mixing at higher throughput rates.
This new low shear design does not use a barrier section but uses almost half of its length as ET sections, thereby achieving an increase in conduction melting of almost 30%.
In addition, processors have found that the Barr VBET provides increased rates, lower melt temperatures and a more uniform melt temperature distribution on all resins run in production.
The VBET has been used successfully in many blown film, sheet, blow moulding and injection moulding applications.
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