Holy PTFE! Why do we use it?

I am really sick of the warping PTFE scenario. I've had PTFE fail me on every *type* (Not manufacturer) of extruder I've had my hands on. I only extrude PLA so I use temperatures lower than people who do ABS.

Is there a system for which this is not a problem?

On designs that have a insulating tube that go all the way to the nozzle the opening of the tube shrinks until filament can;t be pushed through it. The filament starts out ok, but then I can see that after a while it swells from the heat and pressure and can't fit through anymore. Since this is happening just above the extruding orifice it seems unlikely that I could cool the filament enough that far down the extruder.

on Designs that have a PTFE barrel or Hybrid Barrel that connects to a much larger brass piece the opening that allows filament through eventually warps, I can file it out and get through another set of Prusa parts but then when it warps again it's pretty much done.

For people proud of their extruders, what design do you use and how much filament can you push through without maintenance? I want to be able to get through 10 pounds without dissassembling it.

thanks,
-Anthong

I have two extruders with PTFE that is totally constrained. One inside a copper tube with PEEK end cap and the other in Brian's hybrid PEEK cylinder. I run them at 250C 24/7, the copper one for more than a year now, and they are both totally reliable after extruding hundreds of kilograms of ABS. The PTFE has nowhere to go. It can't expand in any direction so remains stable, even though it must be quite soft at 250C.

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[www.hydraraptor.blogspot.com]

thanks, it's good to know that it can be achieved, I wonder if the ABS instead of PLA makes a difference on this.

My extruder hot end design (Wildseyed Simple Hot End) uses a 40-45mm PTFE rod (1/2 inch diameter) drilled out to 3.5mm. This seems to be the sweet spot for not binding warm PLA. Since half of the rod is captive inside the brass coupling, I re-drill the hole after screwing in the rod, just to make sure any compression induced shrinking is removed.

This set up works equally well with ABS and PLA. I've used temperatures in the range from 190C to 220C for PLA, and 230C to 260C for ABS. No problems.

PLA should be less stress on the PTFE because it runs at a lower temperature and is less viscous, so also runs at a lower pressure.

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[www.hydraraptor.blogspot.com]

The problem that PLA has is that it gets soft at temperatures much lower than its melting point, so it expands sideways as it is being pushed.

thanks jacabrer! I think you are onto something great. I want to make a big fat nozzle to put at the end of a fat ptfe barrel like that.