simpler extrusion tube

Has anyone tried just dousing a metal extruder in spray-on PTFE instead of inserting a PTFE tube into a metal support?
This stuff
[www.dowcorning.com]
[www.amazon.com]
Claims up to 450*F/240*C, which is basically high enough.

Edited 1 time(s). Last edit at 02/14/2011 10:04PM by makeme.

Those lubricant sprays would not last, they would be pushed out by the plastic. An actual baked on teflon coating might work though.

The amazon one you linked is a lubricant with PTFE, not really PTFE-only coating. I don't think that would work out well.

The second one is recommended for "Rubber guides, sliding doors, furniture hinges, small mechanism in office machines and sunroof seals" which sounds like just what we're looking for. I couldn't find a price though, you'd have to call you local dow corning distributor and ask.

Somebody referenced a spray-on PTFE coating sold for refinishing guns. Should also be a very durable finish, IIRC was around $35 a can.

However, according to nophead's research on the subject, the transition zone (melt zone) needs to be either short, tapered, OR slippery. I think that getting two out of three should be enough to get a rock-solid reliable extruder no matter which plastic you push through it. Getting all three would be a bonus, and I don't think can be done without some sort of spray-on coating like this. It'd be hard to get it all over the inside of an extruder barrel, but I'm sure it could be done well enough.

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I'm building it with Baling Wire

What about this stuff?
[www.moldreleasenanotechnology.com]
[www.mouldrelease.com]
[www.nanomoldrelease.com]

That looks really nice. Good to 450C, recommended for thermoplastics. Drying time is quite high (8-12 hours) so should be easy to work with.

Costs $47 though. You could do a lot of extruder barrels with that, but very pricey for an individual.

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I'm building it with Baling Wire

I'd be curious to try Teflon ENP plating on metal extruder parts: [www.reliableplating.com]

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