Hello,

A member of the MakerGear Google Group suggested making a PTFE thermal barrier supported by PEEK. I took a total of 3 PEEK insulators, bored them out and pressed in a PTFE liner. The PTFE liner makes contact with the heater barrel. So, the result is a hybrid thermal insulator that should have the strength of PEEK and the slipperyness of teflon. (In theory.) It may even work fine with PLA.

The problem is that I don't have a MakerBot, RepRap, McWire, etc.

Thus far, I have two beta testers who are planning on trying out this insulator to see how well it works. Since I have made a third insulator, I am looking for a third volunteer. All you need to do is test it ASAP and let everyone know how well it works....or doesn't.

Pictures are attached.

I'll also include a heater barrel and nozzle. Parts are free and shipping is on me.

Regards,

Brian

Edited 3 time(s). Last edit at 02/14/2010 01:04PM by reifsnyderb.

Hey, looks good. I have already tested this design since Bits from Bytes uses this system on their extruders. Only difference is that their PEEK tube is only half length, the other half is aluminum.

if i was that far i would be a willing subject, but i am no where near there yet.

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[mike-mack.blogspot.com]

I'm also using this teflon tube in PEEK, but with the Bowden setup. It doesn't have a lot of run time though (It's my second extruder and I'm having a BfB software problem with this Darwin). PLA didn't work with it in initial tests (got too soft higher up and forms a hard-to-push through plug).

Your design is quite similar to what I currently have. I super glued the tube into it after drilling it out to where the brass starts. I made the outside of the tube rough, super glued it there and the connection seems really good. I could put a lot of force on it (wich is important for the Bowden extruder)

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Regards,

Erik de Bruijn
[Ultimaker.com] - [blog.erikdebruijn.nl]

I wonder if the teflon expands inwards, as it heats up, instead of outwards. Since it can't expand outwards due to the PEEK. This would restrict the filament travel.

Do you mean that the PLA formed a plug? I was thinking that the teflon plugged it.


ErikDeBruijn Wrote:
-------------------------------------------------------
> I'm also using this teflon tube in PEEK, but with
> the Bowden setup. It doesn't have a lot of run
> time though (It's my second extruder and I'm
> having a BfB software problem with this Darwin).
> PLA didn't work with it in initial tests (got too
> soft higher up and forms a hard-to-push through
> plug).
>
> Your design is quite similar to what I currently
> have. I super glued the tube into it after
> drilling it out to where the brass starts. I made
> the outside of the tube rough, super glued it
> there and the connection seems really good. I
> could put a lot of force on it (wich is important
> for the Bowden extruder)

Edited 1 time(s). Last edit at 02/15/2010 09:59AM by reifsnyderb.

This is still available.

Brian, I can test it for you if you are willing to post it to the UK.

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[www.hydraraptor.blogspot.com]

PM Sent!

nophead Wrote:
-------------------------------------------------------
> Brian, I can test it for you if you are willing to
> post it to the UK.

Brian I really like your ideas and work.

Not that I have anything anywhere near as reliable as nophead(thank you for your great blog), but I have played with different combinations of PEEK and PTFE and have some pictures you may want to look at @ [ultimachine.com].

The 0.2 is sort of a hail mary play. The PTFE has a little sleeve inserted into the heater hoping the internal pressure forces the PTFE outward and seals it. Untested at this point and highly expected to fail.

I have some fascination with clamping instead of threading my heater together, and mostly have problems with clamping it too hard or not hard enough and the trying to get the PTFE to stay where I want it without leaking PLA everywhere.

I wonder about the glass filled PTFE that stock that is readily available and will probably try something with it next time shopping for that type of stuff. Supposedly more rigid.

If you make more of these Hybrid insulators I would be interested in purchasing one to try. I pretty much only use PLA since I have plenty here

BTW would you be interested in selling your extruder parts on my store ultimachine.com. PM welcome if preferable.

PM Sent.

johnnyr Wrote:
-------------------------------------------------------
> Brian I really like your ideas and work.
>
> Not that I have anything anywhere near as reliable
> as nophead(thank you for your great blog), but I
> have played with different combinations of PEEK
> and PTFE and have some pictures you may want to
> look at @
> [ultimachine.com]
> truder.
>
> The 0.2 is sort of a hail mary play. The PTFE has
> a little sleeve inserted into the heater hoping
> the internal pressure forces the PTFE outward and
> seals it. Untested at this point and highly
> expected to fail.
>
> I have some fascination with clamping instead of
> threading my heater together, and mostly have
> problems with clamping it too hard or not hard
> enough and the trying to get the PTFE to stay
> where I want it without leaking PLA everywhere.
>
> I wonder about the glass filled PTFE that stock
> that is readily available and will probably try
> something with it next time shopping for that type
> of stuff. Supposedly more rigid.
>
> If you make more of these Hybrid insulators I
> would be interested in purchasing one to try. I
> pretty much only use PLA since I have plenty here
>
>
> BTW would you be interested in selling your
> extruder parts on my store ultimachine.com. PM
> welcome if preferable.

Hi Brian,
It was working well for a few days but then suddenly got impossible to push filament through, even with the nozzle removed. Turned out the PTFE liner had slipped upwards leaving a gap for soft but not molten plastic to grip.



I thought the extruder would hold it down but I must have not pushed the PEEK in far enough. I also thought the bolts I put through would nick it but they missed.

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[www.hydraraptor.blogspot.com]

Well I thought that is what had happened. I have just stripped it down, cleaned it and reassembled it. I can't get the PTFE quite flush again. I am sure it was when I received it. It seems like it must have swollen.

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[www.hydraraptor.blogspot.com]

reifsnyderb Wrote:
-------------------------------------------------------
> This is still available.

anymore available? Can work this into my projects.

Nophead,

This confirms the problem with the old hybrid thermal barrier design. Pressing the PTFE in does not work. PTFE deforms too easily and will not stay pressed in over time. Once it starts to move, it's game over.

I have a new design out that has a snap ring installed. The snap ring prevents the PTFE from backing out.

Another change has been made from the old design. Since tightening the barrel down could force the pressed-in PTFE out of the PEEK housing, I had about 2mm of incomplete threads inside in order to stop the barrel from exerting pressure on the PTFE. This greatly contributed to gap formation that has happened to other beta testers. The new design has the threads at full depth all the way through the PEEK in order to properly snug the heater barrel against the PTFE.

Nophead, I'll send an updated version to you tomorrow. Thanks for the great update!

Regards,

Brian

Edited 1 time(s). Last edit at 03/28/2010 04:29PM by reifsnyderb.

Hopefully someone is still watching this forum list.
Our Mendel is in the last stages of assembly, I need to get the extruder built. I have all the material (3/4" pek rod to lathe down, 1/4-28 brass screw to late and drill out) and I remembered this hybrid question. Is there really that much difference in drag between peek and PTFE for the 3mm line? If your extruder motor has a good grip on the imput material, is the drag enough to slow down the process? I also have some PTFE rod that I could create an insert, and lathe in a snap ring groove to hold it in place, but wasn't sure if this is only an issue if you are using PLA. Right now we have both ABS and PLA, but thought we would start with the ABS. I am also planning on putting mounting screws instead of gluing the PEEK into the body, so I can swap out different extruders to experiment with different nozzle diameters without swapping out a complete unit or trying to unscrew the brass from the peek. I have seen evidence that this method has been used, (Nophead's pictures showing a mounting screw in peek) anyone have feedback, pictures, horror stories, things to watch out for?

My experience is that PTFE is much more slippery than PEEK and also a better thermal insulator.

I think you will struggle to extrude PLA through a PEEK only insulator. I have never managed it. It extrudes easily through the hybrid, but when I used it above a heated bed it go too hot at the entrance and the PLA softened and jammed on the taper at the top. ABS is much easier as it doesn't soften till about 90C rather than 50C for PLA, and is less grippy than PLA.

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[www.hydraraptor.blogspot.com]

I was just wondering about a variation on the brass studing/mig welding tip. If the metal tip slowly works its way out of the thermal barrier, then perhaps a larger hole should be drilled, the threads slide all the way through. A second, larger hole from the other side to pass a nut to thread onto the internal end of the nozzle. This nut will then take all the pressure of the plastic filament, an prevent the nozzle from slowly slipping out. Then you will need to insert a liner to narrow the opening in the back from being big enough to pass the nut to just larger than the 3 mm plastic. This would be a good way to use a PEET outer thermal barrier and a PTFE inner lining to provide less friction.

Mike

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Team Open Air
Blog Team Open Air
rocket scientists think LIGHTYEARS outside the box!

Anyone have magic numbers they used for relative diameters and length of peek and ptfe for the Hybrids? if the OD of the Peek is to be 16mm, the OD of the hole through the center is 3.5 mm, splitting the difference makes the PTFE section OD about 10mm? are people making Hybrids putting the PTFE section just in the upper 20mm section, so the brass barrel bottoms out onto the teflon?

Hello,

Here are the dimensions I use for my hybrid thermal barriers:

PEEK housing is the standard 5/8" x 35mm
The side, that the PTFE sides into, is bored out to 3/8" for 3/4" and has a flat bottom.
The snap-ring is installed 0.025 from the edge and the groove is bored out to 0.400
The groove is about 0.025 wide

The other end is drilled out to 5mm and threaded to m6x1.

The threads go all the way through so that the barrel can make contact with the PTFE.

The PTFE insert is 0.700 long and has a 0.35mm hole drilled through it. A 60 degree center drill is used to make the taper in the outer end.

Regards,

Brian

Hi Brian,
i wanna build my `Hammerhead-Nozzle`.



The big threaded rod cut at 30mm and the cap-nut hard soldered with the brass rod.
A longer m6 rod drilled only 2,9-3.0 max to cool it down, because the heat is concentrated only near the cap nut.Heating-wire turned around the big rod.
Isolated by two PEEK-tubes and the termistor in a whole in one side.
Not yet tested!!!.
Erich

Edited 1 time(s). Last edit at 04/21/2010 04:18AM by chris-nobody.

Hi Erich,

... with such a gigantic 'thermal mass' you'll get very long startup times until reaching the extruding temperature

OK, I have built my Hybrid extruder, snap ringed in a PTFE inner section (Thank you reifsnyderb for the details on size, etc) and am wrapping the Nicad wire. I am using clad nychrome from wiretronics rather than fiberglass, we have used this clad wire (I think the cladding is similar to Kapton material) for heaters before, seems to work well. Thanks as well, Nophead, for your explanation as to why PEEK alone would be a problem insulator. My question is an odd one. I know people are using Hybrid or Peek only insulators for strength, What kind of strength are we talking about? Flex strength? strength for the threads to mount the brass barrel? What "failure modes" have people experienced with PTFE that the PEEK solved?

Secoind question. Has anyone had real success bolting the thermal barrier in to place instead of epoxy gluing?? This would allow unbolting the barrier and cleaning it, rather than trying to unscrew the barrel. I know people have tried it, wondered what success there has been
Thanks
Idaholion

The force to extrude is typically tens of Newtons. You really want an insulator than can take at least 100N for some margin.

PTFE goes soft and lets go of the thread in my experience. It will work for some time, but if you have any sort of problem with temperature or a blockage, it swells and lets go of the thread.

I have never tried glueing the insulator. I drill a couple of holes through it and put pins through. On Wade's extruder there are two M3 holes that you can drill through and fit M3 bolts. I wish Adrian had done the same on the official extruder.

Vik uses a single self tapper, which I have also tried. It does work but has to be just the right length. I prefer two bolts or pins.

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[www.hydraraptor.blogspot.com]

Here's a list I got from [www.amsler-frey.ch]), which compares the physical properties important for a thermal barrier of PTFE and PEEK variants. For comparison I also added ABS. PEEK mod. ist PEEK with 10% PTFE, 10% carbon fiber, 10% graphite. Note that heat conductivity is about the same for all. Coefficient of friction is to take with a grain of salt, as it is temperatur/material/(static friction|kinetic friction) dependant.

                            PTFE    PEEK      PEEK mod.  PEEK 30%GF    ABS
Coefficient of friction     0.05    0.30      0.11       ?             0.5
aggainst Steel
yield Stress N/mm*mm        10      100       120        156           45
Elasitc modulus N/mm*mm     500     3900      7800       9600          2400
(stiffness)
heat conductivity W/(K*m)   0.23    0.25      0.24       0.43          0.17
Coefficient of thermal      16.5    4.7       2.2        2.2           9
expansion 1/°C x 1.e-5
working temperature         300     300       300        300           100
short time Celsius
working temperature         260     250       250        250           80
long time Celsius

Hi Markus,

... i was interested in the properties of POM, as it's much cheaper and i have it at hand - so i updated your list:

                            PTFE    PEEK      PEEK mod.  PEEK 30%GF    ABS 	POM-C		POM-H
Coefficient of friction     0.05    0.30      0.11       ?             0.5	0.25-0.32	0.25-0.32
aggainst Steel
yield Stress N/mm*mm        10      100       120        156           45	70		75
Elasitc modulus N/mm*mm     500     3900      7800       9600          2400	3000		3200
(stiffness)
heat conductivity W/(K*m)   0.23    0.25      0.24       0.43          0.17	0.31		0.31
Coefficient of thermal      16.5    4.7       2.2        2.2           9	11		10
expansion 1/°C x 1.e-5
working temperature         300     300       300        300           100	140		150
short time Celsius
working temperature         260     250       250        250           80	100		90
long time Celsius

Edited 1 time(s). Last edit at 04/29/2010 10:03AM by VDX.

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

adding [ code ] [ /code ] around the list helps greatly

... yes, found this too - in the preview it was in correct alignment, posted it was a mess

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Would be useful info to see on the wiki.

/me takes off Sebastien hat.