Could holes be made in the sides of the nozzle

(note the attachments)The idea is to put holes in the side of the nozzle and run (stiff-ish)wires through it, those wires go through a block, are twisted together behind the block. Between the block is a pfte tube so the block pushes it into the back of the nozzle.

The nozzle end is stuffed as tightly possible with aluminium foil/tape and the thermistor. The heater resistor would kindah have to hang on there, thermally connected by aluminimum bits. Kapton/maybe some putty could keep the aluminium bits together and insolate the outside.

The cold end could also try use aluminium foil touching the filament to provide better conductivity than pfte. In the case of foil, the worry is that some could get loose and flow down blocking the nozzle.(This tape stuff seems solid though)

I am not trying it because i dont have acorn nuts or drills of the right description. And it sounds like a potentially stupid idea It would cut down on machining a lot, basically just drilling the extrusion hole, and those four wire holes, if you dont feel like you need tapering.(tapering is going to be nice to have if slicers ever leave the flat-layer-by-layer idea.)

It could fail by simply leaking plastic in the front(seems most likely, but not sure at all if that would actually happen), those wire connections not being decent and loosening over time, the heater resistor not having good enough thermal contact, causing PID problems, not enough cooling at the cold end.(is that it?)

In writing the openscad visualization, i noticed the acorn nut needs to be quite large, its like 1cm inner diameter in there. (8mm pfte tube + room for thermistor needed)

So what do you think?

Why?
A block of aluminum / copper with heater attached and nozzle
provides a Hot zone for filament to melt and be pushed out thru nozzle.
A way to transmit heat from cart heater or resistor to the fliament to be melted.
Nozzle providing a small hole 0.20, 0.30, 0.35, 0.40mm for a fine extruded filament
for printing?

What is WRONG with the nozzle being threaded into a hot block?

Looks like you are trying to isolate a hot nozzle from rest of extruder?
I don't think the PTFE alone would contain the pressures envolved
It gets soft at extruder filament temperatures.

Perhaps your fixing something that is NOT broken.

Because (in the spirit of making things more reprappy)it eliminates vitamins that might not be available, and requires no machining other than drilling. Basically it is the brass acorn nut, metal wire, pfte tube, aluminium foil and tape.

And the hot end is ~nr3 in price, though 'only' 12% in my calculation. Of course the hot end is critical and not something to skimp on if that increase the probabilty of failure any, but i like trying to develop things, hence the suggestion, i might try it..(nr1 is electronics 34%, nr2 motors, 22%, the rest is all over the place, of course this is merely my somewhat tentative calculation.. Changes most likely decrease these percentages)

Hmm you're right PFTE will creep and expand. Basically then you have to tighten the thing up again. Maybe a metal wire can be wrapped around the pfte tube to limit the creep.

You're also right in that there might not be enough thermal contact between the filament and the hot end.(I can calculate this when i am less tired..)

> Perhaps your fixing something that is NOT broken.

I am not thinking in terms of fixing things. Maybe you should change the angle from which you're looking at this.

Rep Rap is printers making other printers
What does this have to do with that.

Drilling small holes thru a small 1/4" acorn nut NOT easy!
Avoid drilling thru central hole even harder.

Have you ever done any machine work?

Eiminating a 2 cent block of aluminum to eliminate ALL the heat transfer
Eliminating a pressure vessel that is mandatory

This is NOT the place to use Play doh and tape!!!! 200 deg C

> Eliminating a pressure vessel that is mandatory

You say it like a teacher told you with authority. Not convinced.

I havent machined(substractively), however, the feasibily of drilling is easily sufficiently plausible for me, it'd basically be this approach, but with a little printed tool to hold the acorn nut on its side.

The front end is 2mm diameter, so ~ 3mm² surface area, thermal conductivity is 0.2W/mK or something, so 3mm²⋅0.2W/mK / 0.5mm ≈ 10^-3W/K. The heat capacity is 1.7J/gK, so to heat by 200K around:

rate_of_mass_heated = power_per_kelvin⋅temperature_difference_required/heat_capacity =
10^-3W/K⋅200K/(1.7J/gK) = 0.1g/Ks

If 1cm/s or 1.75mm filament is fed, thats about ~3mm^2⋅1cm/s⋅1g/cm³ ~3⋅10^-2g/s, which only takes a temperature difference of 3⋅10^-2g/s / 0.1g/Ks = 0.3K, that doesnt look problematic to me at all. Of course the difference is quite larger because heat conducts out via the PLA too.. Too lazy to calculate, but i do not think that increase the temperature difference needed by too much.

A whiteboard with all your calculations on it won't print parts.

Please make a video of this drilling operation.

Threads on nozzle and heater block much stronger and easily made.

Please show how the heater ( resistor or cart heater) will interface to this
to efficiently transfer heat.

When your disaster under pressure spews 200 C deg plastic over your hand or face
you will know the value of a good pressure vessel.

HOT under pressure ---- Please be safe!

Jasper1984 Wrote:
-------------------------------------------------------
> > Eliminating a pressure vessel that is mandatory
>
> You say it like a teacher told you with authority.
> Not convinced.
>
> I havent machined(substractively), however, the
> feasibily of drilling is easily sufficiently
> plausible for me, it'd basically be
> t
> his approach, but with a little printed tool
> to hold the acorn nut on its side.
>
> The front end is 2mm diameter, so ~ 3mm² surface
> area, thermal conductivity is 0.2W/mK or
> something, so 3mm²⋅0.2W/mK / 0.5mm ≈
> 10^-3W/K. The heat capacity is 1.7J/gK,
> so to heat by 200K around:
>
> rate_of_mass_heated =
> power_per_kelvin⋅temperature_difference_required
> /heat_capacity =
> 10^-3W/K⋅200K/(1.7J/gK) = 0.1g/Ks
>
> If 1cm/s or 1.75mm filament is fed, thats about
> ~3mm^2⋅1cm/s⋅1g/cm³ ~3⋅10^-2g/s,
> which only takes a temperature difference of
> 3⋅10^-2g/s / 0.1g/Ks = 0.3K, that
> doesnt look problematic to me at all. Of course
> the difference is quite larger because heat
> conducts out via the PLA too.. Too lazy to
> calculate, but i do not think that increase the
> temperature difference needed by too much.





The video in your link shows how easy it is to drill those tiny holes.
I had to do that at work a few times on one off projects.

As long as you use the correct pressure, you'll be fine.

cozmicray Wrote:
-------------------------------------------------------
> Rep Rap is printers making other printers
> What does this have to do with that.
>
> Drilling small holes thru a small 1/4" acorn nut
> NOT easy!
> Avoid drilling thru central hole even harder.
>
> Have you ever done any machine work?
>
> Eiminating a 2 cent block of aluminum to eliminate
> ALL the heat transfer
> Eliminating a pressure vessel that is mandatory
>
> This is NOT the place to use Play doh and tape!!!!
> 200 deg C




Here's the YouTube link for drilling tiny holes:

[www.youtube.com]

That video is drilling center hole!
That is pretty amazing video
but I don't think a common acorn nut provides a smooth chamber
for filament flow?

Jasper is drilling 4 holes at a right angle to the center axis.
and some how not piercing the center channel to attach
nozzle to extruder.

cozmicray Wrote:
-------------------------------------------------------
> That video is drilling center hole!
> That is pretty amazing video
> but I don't think a common acorn nut provides a
> smooth chamber
> for filament flow?
>
> Jasper is drilling 4 holes at a right angle to the
> center axis.
> and some how not piercing the center channel to
> attach
> nozzle to extruder.
>
>



You're right, but here is what I use for drilling those tiny holes at home.:


[www.foredom.net]


These tools are dynamite for small home fabrication.....not many operations that you cannot do.
and, they are so sturdy; they are truly a "Once in a lifetime" purchase.

Do you just hold them like a dentist and drill the little holes?

I still don't see how one would drill 4 holes in the nozzle
at right angles to axis and NOT drill thru the nozzle exit,
when threaded attachment a no brainer?

Yeah, I don't see that part either.....unless he meant "Stopped holes"?

Just like a dental handpiece.

Fantastic tools, used them almost everyday, while grinding and polishing dies at work.

Retired nowadays, but couldn't live without my Foredom.

Here's an example of a "Sensitive Drill Press".:


[www.dumorecorp.com]


Third tool down, but they get awful pricey.

You can do the same thing with a Foredom, using a light touch......"Machinist's Feel".

This is how i thought to use a chuck to drill those holes in the sides: I might put the acorn end at a bit of an angle so the drill isnt at an angle at the location the side hole has to go.

Also, note that the pfte is going to creep, but i dont think that will end up being a problem that defeats this approach.

This might take a while before i try it, havent even figured out where to get the stuff yet. Having trouble finding it. (And i dont want to pay too much, just some acorn nuts and small drills..)

Can you mill a small, flat surface; before starting your side holes?
That will prevent "Wandering".

Do the side holes, go all the way through?

In other words, how deep will the side holes be?

The holes go all the way through. If you look at the picture in the first post, the idea is to run wires through the sides and then down into the pair of holes below and are twisted together behind the block. The pfte tube goes between all that and it pushed into the acorn nut.

I might actually make that block a pair of blocks, and connect the two with screws. The block further away would push the pfte tube. The reason is that i can more easily tighten the screws than the twisted wires. (However, the distance to the cooling zone shouldnt be made too large...)

See why i think it might not work due to leakage Its not going to squirt or anything, only the front.

Oh, i made the diameter-vs-radius mistake.. So everything in those scad files earlier is basically double the size it should be..

To be honest, at this point i think we might be starting to overanticipate. I finally found the stuff i need for it. Got m4 100 dopmoeren,(so if you're near eindhoven and want some.. ) found a 0.5mm drill. (also got some other shit)

Edited 1 time(s). Last edit at 10/21/2013 04:01PM by Jasper1984.

How about using a aluminum or copper washer with holes drilled in it.

The washer could provide a good way to attach heater and get heat into the acorn nut.

I tried reproducing the nozzle manufacturing wiki, but havent succeeded yet. I couldnt get the drill centered. I think it rotates fast enough,(not sure how fast that exactly..) but in the video he is able to rest his hands on something, the way i was doing i i couldnt. Try again in a different way later. I am green at this..

I didnt, realize how tightly those m4 acorns fit.(4mm do'h) I can screw them onto the pfte tube. Fairly sure that wouldnt work. (I can hardly imagine no-one tried it?)

As for the washer you mean put the washer over the nut as done in one of the picture, and then wire that. Also sounds good. Another idea was to use a metal saw and score around the acorn nut, and run wire around in the score.

Yes hole in washer just as big as acorn but not a big as hex.



"As for the washer you mean put the washer over the nut as done in one of the picture, and then wire that."