posted August 26, 2003 11:49 PM               

I want to extrude PA11 hoses (diameter 5-16mm). I have extrusion experience but know almost nothing about PA extrusion. I know that some companies uses extruders with barrier screw AND grooved feed bush (for bigger pipes), others avoid this because of smearing and use a normal 3-zone screw.

Therefore I have following questions:
1) How should the feed section looks like ? Also cooled ?
2) Screw design: Is normal 3-zone screw okay ? Any other design suggestions ?

3) Calibrating: I want to use a small disc calibrator and vacuum tank ? Is it okay ?

I want to hear your suggestions first before I contact the machinery supplier. One further question: Which manufacturer can you recommend for such extruder and downstream equipment ?

posted August 27, 2003 08:01 AM               

Nylon has a tendancy to slip in the feedsection, and as a result many use a modified grooved feed section to assist feedrate and thereby extruder output. My own advice would be to use a modified grooved feed, say 4 to 6 grooves approximately 0.060" deep X 3/16" wide X 1 1/2 diameters in length. As well, I'ld steer clear of the barrier design and consider a short transition design; something on the order of 3 to 4 diameters at most. I've come across those who, w/ longer transitions, have experienced voids or "canoes" on their pipe due to entrained air (presumably due to the rapid phase change of the highly crystalline nylon).

tom black

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Thomas Black
PPS, Inc.

posted August 27, 2003 09:48 AM               

I don't think there is a lot of design experience in Nylon 11 available to pull from.

The design proposed above is typical of nylon design, but I think Nylon 11 is a different animal. The poposed design will work if run slowly.

I have the tools available to explore design options for you project. Please email me if you are interested in discussing them further.