I noticed makerbot is selling PTFE coated nozzles. The idea being that the PTFE prevents plastic from sticking to your nozzle then breaking off after it balls up a bit. This sounds like a good way to improve print quality and make the machine less sensitive to bad skeinforge settings.

Is there a chemist or someone here who knows of a good no-machining (or minimal machining - read "hand held drill only") way to achieve this? I had a couple of thoughts, but I'm doubtful of producing consistent/working results.

First was to chemically dissolve the PTFE and dip the nozzle in it. Given the chemical resistance of PTFE, this seems tricky right from the get go. It has to dissolve PTFE, but not brass. Even if a suitable solvent could be found, it probably wouldn't lend itself to "at home" style experimentation very well either.

Second was to heat the nozzle and press it into a PTFE block. If the nozzle were roughed up, this might create a good bond, but you would have to press it in straight or you would end up with gaps between the PTFE and nozzle. A pilot hole would probably have to be drilled first. Keeping the nozzle at just the right tempurature while pressing it in might be tricky.

Third was some PTFE heat shrink, but I have no idea what size would work best or if such a thing even exists. Buying a bunch of different size ptfe tubes could get expensive quick. It might not seal tight against the tip of the nozzle either. If it didn't pull tight all the way around, it will probably make things worse.

... for highly corrosive atmospheres we use Parylene-coated sensors - this is made in vakuum and could be compared with a PTFE coating.

I think in high counts this could be a usefull addition, as the service is pricey ... so more suitable for shops or group-buys than for single DIY ...

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Viktor
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I had googled this and one of the things I was thinking about was this spray on, household oven cured, teflon coating that is made for guns:

[www.brownells.com]

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Tony Buser http://tonybuser.com * http://reprap.org/wiki/User:Tbuser#Projects

On its surface, that looks like a great solution. I'm not quite convinced enough to give it a try myself though. It seems to be getting mixed reviews as far as durability goes. At $33 plus shipping per can, I would like to hear from more people before trying it myself. The cost would be more acceptable if I knew I would have another application for it at some point, but nothing else comes to mind.

I don't see any kind of prolonged temperature rating either. It sounds like this paint contains a mixture of other materials, so it may not handle extrusion temperatures for hours on end. I'm reminded of the time I bought some refactory cement to cover my heater thinking "Rated to 1500F, this should work great!" only to have a pile of crumbs on my build plate 30 minutes after the first test.

If it did work for coating the nozzle, it might be interesting to try coating the inside of the barrel too.

I bought some 1mm thick PTFE plate, etched one side... I use silicon high-temp gasket maker to glue it on the outside of my resistor block... I gain some insulation, as well as the non-stick surface.

Al...

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[araspitfire.blogspot.com]