Partial PTFE hot end liner

Has anyone tried using a PTFE liner in just the top part of the hot end feeder tube - only going down to about the midpoint of the heat break? It would seem that this is the region where the problems occur with all-metal hot ends. (I've don't have too much experience with them myself.) If the hot end is at, say, 300c, even if the cold end were as hot as 100c, the mid-point wouldn't get hotter than 200c, which is OK for the PTFE. The PTFE then would help eliminate the friction problems with softened filament creeping too far up into the cold end.

Yes, E3D V6 is doing that. It's the magic sauce in their $80 hot end that they have sold tens of thousands of.. but it didn't eliminate the jamming according to hundreds of people on their forums.

E3D V6 Forums

Edited 1 time(s). Last edit at 06/29/2015 06:53PM by thetazzbot.

Quote
thetazzbot
Yes, E3D V6 is doing that. It's the magic sauce in their $80 hot end that they have sold tens of thousands of.. but it didn't eliminate the jamming according to hundreds of people on their forums.

E3D V6 Forums

Thanks for the pointer. From their Ed3 V6 promo video, it looks like the V6 is doing something similar, but the PTFE stop pretty high up in the cold end. I'm thinking about bringing the PTFE all the way down to the mid-point of the heat break so that if you do get the semi-melted plug up too high, it will be riding on PTFE instead of stainless.

The e3d v6 lite does it. PTFE actually runs to the tip.

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cat.farmer
The e3d v6 lite does it. PTFE actually runs to the tip.

Yes, the "lite" version looks like a more typical extruder with the liner running the entire length. What I'm thinking of is a high temp extruder (>250c) but where the liner runs down not all the way, but as far as you can go without exceeding its nominal operating temp of ~245c.

You don't even need the liner if you have enough polish on the inside of the stainless heat break. also a thicker walled stainless heat break would do the trick.

Look at the Pico B3. All stainless construction, up to 500c with special brackets instead of abs printed ones.

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thetazzbot
You don't even need the liner if you have enough polish on the inside of the stainless heat break. also a thicker walled stainless heat break would do the trick.

Look at the Pico B3. All stainless construction, up to 500c with special brackets instead of abs printed ones.

I guess this gets to the nub of the matter. Lots of people say all metal hot-ends with no PTFE liners at all can be difficulty to use, especially with PLA. Is this just because people are using unpolished stainless feeder tubes and if they were all polished properly, printing with PLA would not be an issue? PTFE will certainly have lower friction than even polished stainless, but is that extra margin of slipperyness really needed? I have no idea myself - I'm curious what experience other people have had.

I mostly print in PLA, but occasionally I would like to print with higher temp materials.

I´m using the makerbot MK8 all metall hotend without PTFE. Never noticed friction issues in my coldend, probably from good cooling?
When I pull out the PLA after a print, it looks like the lowest end is thicker. It has expanded upto the wall of the heatbreak.
All I notice is, it takes one or two skirt lines before the filament starts to extrude.
I have 3mm extra-extrude in my startcode, maybe a bigger value would help here too?
-Olaf

Edited 1 time(s). Last edit at 06/30/2015 02:43AM by o_lampe.