Is there any alternative to Teflon?

I've been at this for some time, following noophead, Q'bd, etc.

Basically, when you push filament through a hotend, it goes from solid, to tacky, to honey in consistency. During this transition, it goes from low friction to ultra-high friction to low friction again. As a result, pushing on a tacky, half-melted region of plastic causes the forces to go sideways instead of out, and you end up with a useless extruder.

By design, most extruders use polished stainless and a cooling fan. This is important. The cooling fan combined with low thermal conductivity stainless causes the melt transition region to become so much shorter, that SOME of the forces go sideways, but not all. For the forces that do go sideways, the polish helps reduce friction. In addition, a taper DOES not in fact help as I originally thought. Instead, it encourages filament to move "sideways" and causes clogging all the same. By contrast teflon has none of these problems.

I've tried alumina ceramic, kapton-coated aluminum, aluminum, stainless, wood, tapered metal holes, inverse tapered holes, and more. None of these work like the existing solutions.

So, what is so incredibly special about teflon that makes it work, without a cooling fan, and it completely resilient to getting stuck? Is it just the lower friction? What are the disadvantages? Does Peek work (as a lining material)? How about ultem? How about glass-filled teflon?

Why did people switch to all metal hot ends, and add a loud fan to the system, when teflon was working?

---

Measure once, Cut twice, Print 3 times.

teflon is slippery and chemically inert , PLA bonds strongly with PEEK which is why it isnt used

People switched to all metal hotend for a variety of reasons mainly because you can take them to some really stupid temperatures in relative safety, (personally i've gone as high as 560c),

however... people in general have also expected pretty much all the all metal hotends to still be a general purpose hotend eg can extrude everything and have really been spolit by the jhead (which is still the benchmark).

realistically certain materials and sizes are better suite to particular types of hotends




Simba Wrote:
-------------------------------------------------------
> I've been at this for some time, following
> noophead, Q'bd, etc.
>
> Basically, when you push filament through a
> hotend, it goes from solid, to tacky, to honey in
> consistency. During this transition, it goes from
> low friction to ultra-high friction to low
> friction again. As a result, pushing on a tacky,
> half-melted region of plastic causes the forces to
> go sideways instead of out, and you end up with a
> useless extruder.
>
> By design, most extruders use polished stainless
> and a cooling fan. This is important. The
> cooling fan combined with low thermal conductivity
> stainless causes the melt transition region to
> become so much shorter, that SOME of the forces go
> sideways, but not all. For the forces that do go
> sideways, the polish helps reduce friction. In
> addition, a taper DOES not in fact help as I
> originally thought. Instead, it encourages
> filament to move "sideways" and causes clogging
> all the same. By contrast teflon has none of
> these problems.
>
> I've tried alumina ceramic, kapton-coated
> aluminum, aluminum, stainless, wood, tapered metal
> holes, inverse tapered holes, and more. None of
> these work like the existing solutions.
>
> So, what is so incredibly special about teflon
> that makes it work, without a cooling fan, and it
> completely resilient to getting stuck? Is it just
> the lower friction? What are the disadvantages?
> Does Peek work (as a lining material)? How about
> ultem? How about glass-filled teflon?
>
> Why did people switch to all metal hot ends, and
> add a loud fan to the system, when teflon was
> working?

---

-=( blog )=- -=( thingiverse )=- -=( 3Dindustries )=- -=( Aluhotend - mostly metal hotend)=--=( Facebook )=-

the metal hot ends are still described as experimental.

where? ... not all of them

---

-=( blog )=- -=( thingiverse )=- -=( 3Dindustries )=- -=( Aluhotend - mostly metal hotend)=--=( Facebook )=-

You could try to experiment with nanocoatings. At least some of them are even oil repellend, which is similiar to molten plastic. Only if they can withstand the heat and how long the coating will last seems to be critical to me. But it wont cost much and you can apply the coating to any material fast and easy. Maybe there is a better suited coating for the high temperature purpose than this one here:

Nano Coating Video

Good luck!

Marcel

---

Blogs:
Meine 3D Druck Abenteuer
[3dptb.blogspot.de]
FLSUN Delta Drucker für Deutschland
[flsun-deutschland.blogspot.com]
Books on 3D patents:
[goo.gl] (english)
[www.amazon.de] (deutsch)

What makes PTFE so special is the fact that it has VERY low friction, low thermal conductivity, and can withstand relatively high temperatures (enough for ABS extrusion). It has all of the necessary characteristics of a hot end insulator. Hot end developers have yet to find a material that is a more effective than PTFE in this regard.

The only time PTFE is not used in hot end design is when we are trying to reach temperatures above ~240C to print Nylon/Polycarbonate as PTFE really starts to break down above this temp. This is why people have started designing "all-metal" hot ends.

Eric

PTFE is used as a non-stick coating for pans and other cookware, so if you find a pan that boast a different kind of non-stick coating then that might be an alternative to explore.

clever...
"where can I find a non stick coating, and heat"
: )

Edited 1 time(s). Last edit at 10/15/2013 11:08PM by Simba.

Teflon still has the problem of creep. Especially for ABS temperatures, teflon will slowly widen and create leaky holes at the junction between cold and hot. This will result in plastic leakage around your hot end.

Even in the J head design, the teflon liner can still get squished over time and create a gap between the liner and the nozzle taper. This in turn will cause your hot end to become less responsive to retraction and increase oozing.

This is why most people are switching to all-metal designs because in my opinion they have none of the problems of teflon. The fact that it seems difficult to control the heat traveling up through the thermal break is just a technical detail that will soon be overcome once people realize you need proper cooling on the "cold end" and none of these microscopic 2-cm fans that E3D has made popular.

Maybe you could even chemically coat the inside of a stainless steel thermal break with teflon in exactly the same process used to coat stainless cooking pans. That would be the best design.

destroyer2012 Wrote:
-------------------------------------------------------

> Maybe you could even chemically coat the inside of
> a stainless steel thermal break with teflon in
> exactly the same process used to coat stainless
> cooking pans. That would be the best design.


already looked into it, the cost is a little crazy

---

-=( blog )=- -=( thingiverse )=- -=( 3Dindustries )=- -=( Aluhotend - mostly metal hotend)=--=( Facebook )=-

Graphite loaded PEEK sold as Tekapeek by RS 297-0147, £11.88 for 300mm of 10mm dia. I have tried this in the liner of a hot end but it was not a success -possibly for a reason unrelated to the material. i will try again in the future when I am not firefighting just to keep the damn thing running.

Mike

Quote
JGR
destroyer2012 Wrote:
-------------------------------------------------------

> Maybe you could even chemically coat the inside of
> a stainless steel thermal break with teflon in
> exactly the same process used to coat stainless
> cooking pans. That would be the best design.


already looked into it, the cost is a little crazy

That's a pity Teflon coated SS would be the perfect thermal break. Have you tried coating the filament in Teflon as it enters the hot end? I am not sure if this would be very effective but it's worth a try.

Eric

Quote

In addition, a taper DOES not in fact help as I originally thought.

Yes it does if it covers all of the transition zone. It works like a mould relief taper. It prevents the rubbery part of the filament gripping the wall as any forwards movement causes it to part from the wall. Below the taper the filament is liquid and above it it is solid.

The all metal extruder I made (probably the first in the Reprap world) used stainless steel pipe which was not very smooth on the inside and certainly not polished. It worked well with PLA, ABS, PCL, PMMA and HDPE. It didn't work reliably before I added the taper.

---

[www.hydraraptor.blogspot.com]

RP Iron Man Wrote:
-------------------------------------------------------
>

Quote
JGR
> destroyer2012 Wrote:
> --------------------------------------------------
> -----
>
> > Maybe you could even chemically coat the inside
> of
> > a stainless steel thermal break with teflon in
> > exactly the same process used to coat stainless
> > cooking pans. That would be the best design.
>
>
> already looked into it, the cost is a little
> crazy
>

>
> That's a pity Teflon coated SS would be the
> perfect thermal break. Have you tried coating the
> filament in Teflon as it enters the hot end? I am
> not sure if this would be very effective but it's
> worth a try.
>
> Eric

it's on the todo list,

---

-=( blog )=- -=( thingiverse )=- -=( 3Dindustries )=- -=( Aluhotend - mostly metal hotend)=--=( Facebook )=-

nophead Wrote:
-------------------------------------------------------
>

Quote

In addition, a taper DOES not in fact help
> as I originally thought.

>
> Yes it does if it covers all of the transition
> zone. It works like a mould relief taper. It
> prevents the rubbery part of the filament gripping
> the wall as any forwards movement causes it to
> part from the wall. Below the taper the filament
> is liquid and above it it is solid.
>
> The all metal extruder I made (probably the first
> in the Reprap world) used stainless steel pipe
> which was not very smooth on the inside and
> certainly not polished. It worked well with PLA,
> ABS, PCL, PMMA and HDPE. It didn't work reliably
> before I added the taper.

Did it use a cooling fan?
Im on a mission against the cooling fan. They are too loud (try running 3 Up! printers side by side).

Quote
JGR
it's on the todo list,

Ok, be sure to post your results here when you do get around to it. If coating the filament in Teflon works effectively enough, the manufacturing of all-metal hot ends would be made much simpler

Eric

Yes it needed a small fan but it wasn't noisy compared to the rest of the printer.

---

[www.hydraraptor.blogspot.com]

Interesting. I found that too, you are right that a taper helps, and that you need a fan to see there is difference between tape and not.

mechanically, I'm not sure why a ~5mm transition region is okay, but a 10mm transition = a total failure. You would think if the diameter of the stainless piece is 2 mm, that the forces would be absorbed easily within a 1:1 aspect ratio, maybe even over only 2mm of length.

So in conclusion for this thread, are we all agreeing that we think teflon works because of the low friction...If this was a navier stokes equation, the no slip condition on the wall is really small...

Simba Wrote:
-------------------------------------------------------
> Interesting. I found that too, you are right that
> a taper helps, and that you need a fan to see
> there is difference between tape and not.
>
> mechanically, I'm not sure why a ~5mm transition
> region is okay, but a 10mm transition = a total
> failure. You would think if the diameter of the
> stainless piece is 2 mm, that the forces would be
> absorbed easily within a 1:1 aspect ratio, maybe
> even over only 2mm of length.
>
> So in conclusion for this thread, are we all
> agreeing that we think teflon works because of the
> low friction...If this was a navier stokes
> equation, the no slip condition on the wall is
> really small...

there are other complex factors around the effectiveness of retraction in ptfe lined and non ptfe lined hotends particularly with ooze, this is one of my latest nozzles

click here

bear in mind that photo was taken 30minutes after the filament was retracted 10mm and the hotend left running at 190c , this somthing i did to test how viable this nozzle would be in a dual extruder setup, this is somthing that has never worked with an all metal setup

Edited 1 time(s). Last edit at 10/16/2013 05:46PM by thejollygrimreaper.

---

-=( blog )=- -=( thingiverse )=- -=( 3Dindustries )=- -=( Aluhotend - mostly metal hotend)=--=( Facebook )=-

Could you repost that image?

Are you saying teflon is better for retraction?
That would agree with what I've found here, that metal has friction, its just lessened by fans, tapers, and polish... so if you try to retract the force on the walls should cause the retracted filament to just stretch rather than actually pull up.... interesting

When you retract the rubbery filament stretches lengthways and so pulls away from the walls and does not jam. This is why you can always pull PLA out even when it it not go forwards at all.

It is not a case of a bit more friction means a bit more force is required, There is a critical limit on the coefficient of friction and the length of the transition zone, above which it simply jams solid because of positive feedback. I.e. the more force you apply the more outward pressure you get so that multiplied by the coefficient of friction means you have an equal increase in grip, so it doesn't move.

---

[www.hydraraptor.blogspot.com]

And therefore the metal solution is to not change the coefficient of friction, but make this zone as short as possible?
Did the other printers (before darwin) use Teflon?


nophead Wrote:
-------------------------------------------------------
> When you retract the rubbery filament stretches
> lengthways and so pulls away from the walls and
> does not jam. This is why you can always pull PLA
> out even when it it not go forwards at all.
>
> It is not a case of a bit more friction means a
> bit more force is required, There is a critical
> limit on the coefficient of friction and the
> length of the transition zone, above which it
> simply jams solid because of positive feedback.
> I.e. the more force you apply the more outward
> pressure you get so that multiplied by the
> coefficient of friction means you have an equal
> increase in grip, so it doesn't move.

Printers before Darwin? Darwin was the first RepRap printer! It used PTFE for its slipperiness and good insulation. Unfortunately it also used it for structural strength, which was a mistake as it always fails due to creep. Hybrid PEEK / PTFE solved that problem.

As far as I can remember the only successful hot ends that have a long transition zone use PTFE. With any other material the transition must be short and that requires a fan or a big heatsink.

The Archol one uses a very thin wall stainless steel tube and that only has a small heatsink but possibly also needs a small fan and is very delicate.

Many combine the worst of both worlds and have stainless steel with a PTFE liner and a heatsink and a fan.

---

[www.hydraraptor.blogspot.com]

Seems like there is a whole world of high temp / low friction coatings:

http://industrialcoatingsworld.com/low-friction-coatings/


It would be interesting to experiment with some of these.

LoboCNC Wrote:
-------------------------------------------------------
> Seems like there is a whole world of high temp /
> low friction coatings:
>
> [url=http://industrialcoatingsworld.com/low-fricti
> on-coatings/]http://industrialcoatingsworld.com/lo
> w-friction-coatings/[/url]
>
>
> It would be interesting to experiment with some of
> these.

aside from cost most of them don't really have any temperature limits higher than ptfe tube anyway

---

-=( blog )=- -=( thingiverse )=- -=( 3Dindustries )=- -=( Aluhotend - mostly metal hotend)=--=( Facebook )=-

I still think with all the hype about metal hot ends the general user needs to know to stay away from them. all of them are still considered experimental. none of them have a 100% track record, and all of them require extra parts, fans, calibration that a new user will likely not be familiar enough to handle.

jamesdanielv Wrote:
-------------------------------------------------------
> I still think with all the hype about metal hot
> ends the general user needs to know to stay away
> from them. all of them are still considered
> experimental. none of them have a 100% track
> record, and all of them require extra parts, fans,
> calibration that a new user will likely not be
> familiar enough to handle.


a jhead needs a fan...

---

-=( blog )=- -=( thingiverse )=- -=( 3Dindustries )=- -=( Aluhotend - mostly metal hotend)=--=( Facebook )=-

It's borderline. If the heater block is well insulated to stop convection and the carriage has holes to stop it trapping heat it works without a fan. I think the MK4 was better than the MK5 as I never had any problems with PLA in that without a fan.

---

[www.hydraraptor.blogspot.com]

> Even in the J head design, the teflon liner can still get squished over time and create a gap between the liner and the nozzle taper. This in turn will cause your hot end to become less responsive to retraction and increase oozing.

What if there is a force down the pfte tube, if it creeps, the force just pushes the pfte tube further down. Thats the idea here, anyway. Of course, it would still widen, and so might the PLA which can cause problems retracting.(In the case of the j-head i use kapton/aluminium tape to limit the widening a bit. Also it helps that the walls become thicker; the inner radius expands less than the outer radius.)

Based on that i might try this idea.(I think it will probably leak though?)

Edited 1 time(s). Last edit at 10/17/2013 07:48AM by Jasper1984.