Extrusion Know How
New Frontier for Single Screw R&D: Mixing & Melting by Extensional Shear
Extensional shear generally has been associated only with twin-screw extruders. However, I am now convinced it can be done with a single moving force (screw) by changing the geometry of the flow field perpendicular to the direction of flow.
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The Power-Law Coefficient
By referring to the power-law coefficient, the effect of barrel override in the metering section of many screws can be explained and anticipated.
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Mission (Nearly) Impossible: Estimating Extrusion Melt Temperature
Extrusion processors often ask screw designers to estimate the output and melt temperature of a new design in the works. Projected output of a new screw can usually be estimated fairly accurately. Melt-temperature estimate, however, is another story
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Get Smarter on Extruder Sizes
Processors tend to recommend a much larger extruder than what鈥檚 really necessary for the job and the capabilities of the downstream equipment.
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What’s the Deal With High-Speed Extruders?
If we are talking about extruder screw speed, how about 1800 rpm? That鈥檚 how fast some extruders are running today.
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Water, Oil, Air, or None?
There is no one 'best' barrel cooling medium, but there seems to be a shift in the industry toward air cooling.
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Well, It Worked on Brand X
You need to give your designer a lot more data than that to make sure you get a screw that's right for you.
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‘Wedging’ Can Cause Severe Screw Wear
In a column I wrote for the July 2011 issue, I discussed the value of conducting “forensic” examination of worn screws when they are removed for clues to design flaws.
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