Which hotEnd?

I cant get any statistics by myself, but i assume that in general, the way the hot end fails, is because the M6 thread inside the PTFE fails. Is this correct or there are other ways it "dies"?

Hello,

Assuming normal use, yes, that is the way people have reported the failures. The M6 threads fail and the plastic leaks out. I am not sure whether or not the entire nozzle has popped out entirely for anyone.

(I don't have any statistics, either. I am just going by what I have seen reported in the blogs and on the boards.)

Regards,

Brian


NoobMan Wrote:
-------------------------------------------------------
> I cant get any statistics by myself, but i assume
> that in general, the way the hot end fails, is
> because the M6 thread inside the PTFE fails. Is
> this correct or there are other ways it "dies"?

Edited 1 time(s). Last edit at 04/12/2011 02:05PM by reifsnyderb.

YES, that is how it happens...

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

While that is not PTFE, I got the hint. I just sent you a PM.

Regards,

Brian


rhmorrison Wrote:
-------------------------------------------------------
> YES, that is how it happens...
>
> [www.rmorrison.de]

I want to try some different approach and a certain variation on the hot end subject.

Is anybody interested to really try or test alternative ways of doing the hot end? Or at least give an informed opinion.

I find that Stoffel15's design works very well.



Have printed 6 Kg of PLA with it over the last 3 months.

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

NoobMan Wrote:
-------------------------------------------------------
> I want to try some different approach and a
> certain variation on the hot end subject.
>
> Is anybody interested to really try or test
> alternative ways of doing the hot end? Or at least
> give an informed opinion.

Stoffel15's design looks really nice and I think future designs will be very similar.

Also, I sent you a PM.

Regards,

Brian

My current hot end is with the inside thread and the barrel, and i was thinking the same way about getting rid of it. I am currently waiting it to fail so i can replace it with what i prepared. What i am wondering about, is:

1) if it can work with only one big piece of ptfe alone, and
2) if it can work with same, only one big piece of peek alone.

I understand that peek had issues with friction but unless i am mistaking that was in the design with barrel. So i hope it might work with the filament being driven instantly in a "close to zero height" melt zone like that. Basically driving filament on the very top of 2 heater resistors. Cant see any issues with it, but i am still reticent and i hope it works at least one of the ways with either peek or ptfe at least, so i wouldnt have to bother any further.

In my experience: No and no.

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

I consider different ways to mechanically support it, including having the heater block fixed itself and the thermal barrier being free to expand in height, only 1-2 mm constrained to the sides. If the ptfe is free to move and only fixed in its thread point, i dont think it can ever fail at all, i see no reason for that. If thread fails, i can increase the thread to a M12x1.75mm pitch or maybe even higher.

I cant see anything going wrong with that. But again, thats just me and i am prone to failing aswell. I will make a more detailed wiki page and see what comes out of it.

I don't see how you hope to get a "close to zero height" melt zone with a long insulator. You will have a thermal gradient from hot to cold along the full length of it so it will be above the melting temperature in the lower half. If you have a long transition zone it has to be slippery.

The only way to get a short melt zone is with a short insulator and a heatsink.

If you support the end of the thermal barrier you have short circuited it with the supports, so they too have to be thermally barriers. That is basically how Adrian's latest design works, the hot end is supported by a peek block.

If you constrain PTFE by it ends it may swell in the middle and bulge. The way to ensurre it work is to completely enclose it in something stronger so it is totally constrained.

---

[www.hydraraptor.blogspot.com]

Thanks for the tip, i will have to keep an eye on the gradient and see how it turns out to be.

Dont take the expression per se, i said it like that because i meant it to be way shorter, but i dont exclude the situation where i think something wrong, as i did like that so many times in the past that, i'm used with being wrong.

I assume the ptfe thermal conductivity has about 0.20 W/k*m and the thread is M10 can so it gives roughly a cilinder surface of approx 10*10*pi() + one circle surface of the bottom 25*pi() thus total surface of ~393 mm2. I dont know how to calculate exactly how much heat will go, from thread to ptfe itself, trough that. Please help with that if possible. I would tend to neglect that for myself coz i can *really* insulate it either with special refractory asbestos or with pure asbestos fiber wire. I plan to test first without that anyway. I had in plan to do this stuff like in january but kept delaying it.

However looking at the picture above (which is assumed to work), in that case the contact area is quite a few times bigger, and also it contacts with peek which assumably has at least double higher thermal conductivity. So i believe the gradient of what i putted in picture is at least better. Beside that, if that one works, i have nothing to worry about myself, except maybe the thread, which i think at M10x1.5 can be rugged enough, but if not, i can always thread the other end aswell at M12x1.75 and just switch it around.

Atm one mechanical support version i am considering is to pass 2x M4 screws within the block and constrain them between some insulation plates. This can screw on its turn into the 2 existing vertical screws. The dissipation into the vertical screws should be very limited this way. The insulation materials are mostly available as plates anyways.

A second choice would be to have two metal plates like slightly U - shaped to hold the ptfe fairly close to the heater block, (but still at some range though), and use those to fix the vertical screws in. This way no other insulator is needed, the ptfe alone will act as one, assuming the distance to heater is good enough, and the metal plates will secondary help cooling the ptfe, a little. Better than the peek support in that regard. Still somehow free to expand on height towards the pich wheel, just not so much as before.

Edited 1 time(s). Last edit at 04/12/2011 10:12PM by NoobMan.

@others

About another thing: sorry if the top post was understood like i have items or stuff to give to anyway for testing. I dont, i only made those for myself as exchanges and for obligation i have. Not really interested to buy stuff as i barelly could scratch my wallet for that ones. I rarelly make myself understood, its my bad, again sry for that.

What i meant was if there are ppls interested turn their own materials into a stupid thing like that - and then test about the reliability of it or different impressions. Or if someone has a different version i could cut one of my stuff to try that idea if it seems better.

What do want, is to make a (more or less better) page for hot end topic, that would be aimed at other ppls like me and be mostly DIY. Well DIY, except the ptfe and peek, because we cant print with ptfe yet, but its not excluded if we would use an thermal barrier made out of PBI and if we could get hold of some ptfe filament, who knows, maybe even that can be done No clue if ptfe will stick to previously deposited ptfe though, as usually nothing sticks to it at normal temp.

And i made the page here [www.reprap.org] and putted my consideration there with the "experimental" warning x 3. Anyone, please feel free to edit and make changes as seen fit.

Edited 1 time(s). Last edit at 04/12/2011 07:05PM by NoobMan.

These are some examples (from back in the day) of what PTFE looks like when it fails.

However, if you get PTFE just right, you can get hundreds of hours out of it...there is just very little margin for error...