[MakerBot] Extruder Nozzle Material: Why Brass?

[Brent Crosby]

Is there a specific reason brass is used for most nozzles?

I was looking up the thermal conductivity of materials (ref
http://www.engineersedge.com/properties_of_metals.htm ) and it appears
that aluminum is around twice the thermal conductivity of brass.

In my experience they are about the same effort to machine.

It would seem to me that aluminum would be a better material for the
extruder nozzle.

Can anyone enlighten me on why brass is so pervasive?

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[Oren Beck]

There are several "reasons" both for and against brass as an extruder
nozzle. You may have raised a point simply overlooked by this
community. Potentially speaking, we might consider having anyone with
the production skills, tooling, etc try a few different"Non-Brass"
nozzles and see what, if any substantial changes result. There's a
*LONG* history of some person asking a previously unasked question
that becomes a total situation changer. Here's a factual difference
in education over time that may clarify a factor about Brass:

We used to see a demo in science classes of a brass ball mounted on a
wood handled metal rod, that easily fit thru a steel ring mounted on
an identical handle rod- if both were at room temp. Heating the Brass
ball showed a visual proof of heat expanding metals.The HOT bras ball
would not fit thru the steel ring. The more elaborate science demos
showed the steel ring being chilled in LN or other Cryogen to show how
cooling contracts metals. I am curious of how many people on this list
were shown that demo in their school? Let's not forget that a lot of
MakerBot owner/operators are artistic more than scientific in
background. Though, we do have some people on list who can mentally
calculate the heat expansion factors for a Brass Nozzle compared to
the same factors for other metals. Anyone else have information to
dare we pun-Expand, on this concept of Non-Brass Nozzles?

"Every day teaches me something I thought I knew- was wrong.".

On May 9, 11:25 pm, Brent Crosby <br...@crystalfontz.com> wrote:
> Is there a specific reason brass is used for most nozzles?
>

> I was looking up the thermal conductivity of materials (refhttp://www.engineersedge.com/properties_of_metals.htm) and it appears

[Cid Vilas]

I believe that aluminum would work great if you are printing within a heated chamber.  Otherwise the aluminum would have difficulties maintaining temp.  It will heat up faster but will also cool faster if hit by a breeze or something.  I think i have seen a few extruder prototypes or custom tips in the blog-o-sphere, but the common heater is brass.  I suppose that if you insulate the outside enough it would work great.

--
Cheers,
Cid Vilas

[Jordan Miller]

you actually don't want a very very high thermal conductivity for the
barrel because you need a thermal gradient to print well. you want the
plastic warming slowly as it travels closer to the hot end, then
melting very close to the tip. stainless steel has a very poor thermal
conductivity, and nophead showed it was too low for printing (not
enough melting at the top of the barrel). likewise Eberhard and others
have shown that too much heat going up into the PTFE destabilizes the
PTFE and also causes blockages when the plastic melts too high up. so
aluminum would likely be too good a conductor in the current design.

brass is the goldilocks metal, not too insulating, and not too
conductive.

you could probably make one of all-aluminum that would print, but it
would require a very narrow metal connection between the hot and less-
hot end. see Eberhard's designs on the PleasantHardware blog for more
insight and empirical data.

jordan

[Roger Walsberg]

I'm going to try a non-threaded stainless rod that's drilled to the media size, then drilled at .5mm at the end for the nozzle. I don't like the exposed threads/ undercut inside the nozzle that can potentially cause a print material hangup. I think I'll make the stainless nozzle about an inch long and use a fiberglass rod as an insulator. maybe make the fiberglass portion have a flange that would allow it to be attached directly to the extruder body.

--
Thanks. Roger

[Brent Crosby]

Thanks for the comments.

I was talking to a person about this question today. They mentioned
that the aluminum might be eroded by the ABS, citing that prototype
plastic molds made of aluminum are not good for very many shots.

I guess I would be thrilled if I could get my MakerBot to run long
enough to erode an aluminum nozzle into an unusable condition :)

Roger: Please let us see photos when you try your new design :)

Oren: If you look up the expansion of PTFE (~135) compared to brass
(~19) or aluminum (~23). I think that may be why there is perennial
leaking between the brass and PTFE: hotter = looser.

That may be why MakerGear has good success with PEEK (~25 - ~50), it
matches the brass much better.

(ref:
http://www.stormcable.com/uploads/Thermal_expansion_data_table_tb06.pdf
http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html
)

[Oren Beck]

Good point on the PEEK. When we start taking a technology so far
outside the average user's daily skill sets- stuff like this gets
overlooked. I am very curious as to if there's been any serious
attempts at springloaded =like the ball joint in some auto manifolds-
extruder. builds.

On May 10, 8:33 pm, Brent Crosby <br...@crystalfontz.com> wrote:
> Thanks for the comments.
>
> I was talking to a person about this question today. They mentioned
> that the aluminum might be eroded by the ABS, citing that prototype
> plastic molds made of aluminum are not good for very many shots.
>
> I guess I would be thrilled if I could get my MakerBot to run long
> enough to erode an aluminum nozzle into an unusable condition :)
>
> Roger: Please let us see photos when you try your new design :)
>
> Oren: If you look up the expansion of PTFE (~135) compared to brass
> (~19) or aluminum (~23). I think that may be why there is perennial
> leaking between the brass and PTFE: hotter = looser.
>
> That may be why MakerGear has good success with PEEK (~25 - ~50), it
> matches the brass much better.
>

> (ref:http://www.stormcable.com/uploads/Thermal_expansion_data_table_tb06.pdfhttp://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95....