On the cheap side of things I was saying a few posts back that we might get an assembly of a heater ALU block coupled somehow with a ceramic tube in which we should pour cement making sure that we put in the middle a 1.75mm rod that we will later polish somehow using concrete polishing and sealing pastes/liquids that are sold for kitchen countertops for example.

I find now this idea even more compelling after finding this page during my research: http://mollaspace.com/products/concrete-rollerball-pen?variant=359188221. If that kind of detail can be poured out of concrete(cement?) then why can't we incorporate that cheap solution into a cheap hotend.

I think we can come up with something good about this one.

I wonder if this thread is still suited for this discussion. Because we are heading away from the original poster's idea. My opinion is that his solution is hard to improve upon. It's almost perfect for what it is.

Edited 1 time(s). Last edit at 11/07/2015 08:32PM by realthor.

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I think a little bit here on the internals of extruder hotend
may help here.

This is a extrusion device
melting polymer and forcing it out at a specific size
The task forcing polymer thru small orifice without a piston.

The entire route thru must be very smooth to allow transport
of polymer with out resistance, and contain pressure.

The feed material is the piston to force the material thru the device
The feed material must remain cool - solid to act as a piston
driven by mechanical drive

There is a high heat (200deg C) zone to melt the polymer to allow extrusion
(transformed into 0.XXmm printed filament)

The HOT melt area is just below a cold guide area
and something must prevent the cold guide area from getting hot
softening the feed filament and hindering the piston like function of this area

to stop heat flow from the melt zone,
a very low heat conduction material
that can contain the high pressure of the extrusion

Attaching each zone together with High pressure low heat transfer material fitting is the trick.

I think your ceramic is for the heat isolation

how to keep cold zone cold:
--- prevent heat by thermal isolation
--- cool --- draw away heat to keep cool

I used the 2 engineers ceramic hot end
a ceramic piece Shaped like a inverted chess piece)
with a heat block / nozzle attached to bottom
PTFE was used in ceramic to provide smooth passage for filament

Well PTFE melted near top of heater and never extruded again.

2 engineers don't make them anymore.

There are machineable ceramics
Shuttle tile is NOT ceramic -- it is sintered silica
If machined please take precautions -- dust is a lung killer

Good luck in your ceramic nozzle quest

[www.youtube.com]

This guys machine would grind some nice airtight fittings with 1 micron accuracy, I want one of these machines.
would make a lot of things possible.

Thanks for the recap of the problem, and the nasa lesson I knew they where some sort of foam but didnt care about ingredients sand or sea shells just the method ie heat shield tile.

A little like the Nasa ppl not caring about the properties of the O ring, but I'll survive.

Edited 1 time(s). Last edit at 11/08/2015 01:19AM by MechaBits.

if only cement could have threads molded into it that can actually be used to screw metal into it.
I've seen the chesspiece on the web and it has threading cut into the ceramics (http://3.bp.blogspot.com/-GIswVMPtNX8/UKxrhlqm00I/AAAAAAAACls/_I-aE_osyGU/s320/PART_1350468547361.jpg). How is that possible, isn't the ceramics too brittle?

I can't just yet wrap my head around an object with a single smooth channel, that has 2 zones, one for melting plastic and the other for heatbreak but I am quite sure that it will be some sort of ceramic/cement top bottom pen-like tube with an internal metalic ring and an external induction coil. Still something to think hard about... among so other many things to think hard about

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Quote
realthor

I can't just yet wrap my head around an object with a single smooth channel, that has 2 zones, one for melting plastic and the other for heatbreak .

Prometheus hot end

Quote
etfrench

Quote
realthor

I can't just yet wrap my head around an object with a single smooth channel, that has 2 zones, one for melting plastic and the other for heatbreak .

Prometheus hot end

Thanks for the link I've badly chosen my words (english is not my first language).. I wanted to say that I can't really put on paper the hotend that I am envisioning. It's a 3 zone hotend similar to the following image:



The long part is ceramic/cement-based, the interlocked black part is a internal metallic external ceramic part with an outer induction coil of sorts and the tip is ideally ceramic or some other type of nozzle that has a very hard tip (saphire?) that can whitstand abrasive filaments torture.

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I think I'm going to stay with ptfe lined idea for time being,
this doc needs some reading but might help
[www.ceetak.com]

... there are several (expensive) high-tech ceramics specially designed for milling and lathe-shaping (I've worked with Macor) - but limestone (especially the dense types) will do the job too

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Quote
MechaBits
I think I'm going to stay with ptfe lined idea for time being,

Yeah I'm staying with current technology as well, maybe will try the OP's solution for the time being but I've exposed an ideal hotend that i'd like to have, a mind exercise.

The PFTE looks like the real deal for working temps below 260deg C, but if we want higher temp polymers we need to go all metal or all-ceramic, or all-something else that can withstand those high temps.
Metal is the cheapest hence the current breed of metal hotends (bras+ALU+Stainless steel).

Personally I would like to experiment with pouring cement/concrete in molds like in the example with the concrete roller pen. Molds can be even 3D printed. Concrete is easy to polish and there are readily available solutions for it. The only problem is that a heater must be incorporated in the design, which is most likely metal and there is the issue of attaching metal to the concrete part. I am thinking an insert threaded nut can be incorporated in the mold and built in the concrete part before it sets.

Because cement/concrete is quite brittle, I see two possible problems:
1) will temperatures above 300 degrees in the metal part affect the concrete body? How does concrete react to localized high temps. Will it crack?
2) the clamping of the hotend to the carriage must be done some other way than using the actual body through which the filament is routed.

Trial and error will show what is possible.

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Yes 3D printing great for molds, I was going to chime in on the other thread about how it still has its uses for building a decent strong frame, even if the parts just used as a mold for something else.

ohh I can't wait to build or buy my first printer to try improve little things one at a time ...right now I am overwhelmed, opened threads all over this place .

But I will definitely try a cast concrete pen-hotend with induction heating ... I wonder how much would it cost for the small board that poweres it. This will deserve a new thread nonetheless.

Also casting concrete is not that easy as concrete shrinks while curing. How would one compensate for the shrinkage?
Concrete is quite brittle, how can we make a more plastic concrete (yes I know they use plasticizers in ready mixes but still this application might benefit from some customized formula)

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Thermal Conductivity

Table doesn't show strength of material.

Plaster would be great, workable, perhaps wrapped with something to take the pressure

You could check out Corian or maybe the adhesive filler (if it has corian filler in it)

Then again (like the all metal hotends) use cooling suck heat out, blow it away

Induction heating?
see:

[forums.reprap.org]

Quote
cozmicray
Induction heating?
see:

[forums.reprap.org]

Thanks Cozmicray for pointing that thread out. I've only found that on web and with less details.

A great lot on useful info i've found on this resource: [www.rmcybernetics.com]

But really we need a small circuitboard that can achieve the heating. I am sure this isn't the thread to develop this subject but as long as the OP has deserted this thread wwe might as well do. This is no 10 cents hotend anymore but we're driving towards more reliable, better suited to 3d printing hotends.

I am thinking that the induction hotend must have a few charateristics like achievable temp to be upwards 300C, maybe even 500C for the industrial-grade plastics that are starting to pop up, it has to be able to have the induction coil some distance away from the board as to only have on the end effector the coil and must be safe to operate around. I don't know if it is possible cause I am no electrical engineer but maybe some of those brains will stumble upon this thread somehow and have an input.

One of the smallest i've seen is this from 2012: [www.youtube.com] ... I have no idea if those 15V / 10W are enough for 3D printing though.

Edited 1 time(s). Last edit at 11/08/2015 03:47PM by realthor.

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This is my hotend from a fuse and brass coupling, M6 Brass Coupler
It's not tested, I was expecting a compact extruder without a need for fans or heatsink. it looks like the only way to attach this to the x-axis would be a clamp. or making a mold using fire putty may be possible.
encasing a heating block in ceramic would be nice an all in one, heater / nozzle / thermistor. Individually replaceable.

Quote
3DS-QUAD
This is my hotend from a fuse and brass coupling, M6 Brass Coupler
It's not tested, I was expecting a compact extruder without a need for fans or heatsink. it looks like the only way to attach this to the x-axis would be a clamp.

Nice one, similar to the OP's solution, I even like it better. But I am right guessing that it's press-fit into the brass coupling? I hate that those ceramic tubes don't have anything to hold them of. You would have to "inject" some high-heat resistant resin to glue the tube and fill the threads so that the palstic will not creep out.

Quote
3DS-QUAD
making a mold using fire putty may be possible.
encasing a heating block in ceramic would be nice an all in one, heater / nozzle / thermistor. Individually replaceable.

Is this the kind of encapsulated heating block that you are looking for? Encapsulating the heating element in ceramic is good for energy loss prevention but has nothing to do with the heatbreak. We need a way to break the heat conduction from the ALU heating block upwards so that the solidifying of the filament takes place without the need of a heatsink as we know it.

------------

I have found a picture representing very well the way I see the contact between the hotend stages. As I've told before, they shouldn't be straight edges but cones and each segment should be ending in a cone that is pressed by some means into the cone below (threading for metals, ? for ceramic tubes):



The above is from an "Air Bleed Valve", as explained on [inspectapedia.com], a few pages below, at the "Manual Air Bleed Valve Cleaning & Parts" headline.

Edited 1 time(s). Last edit at 11/08/2015 06:07PM by realthor.

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realthor "But really we need a small circuitboard that can achieve the heating"

Why? Circuits in
[forums.reprap.org]

shows what has to be close to inductive heater and what is remote?

Extruder pix with red hotend:

The red stuff around heating element in pix
is Silicone rubber
NOT ceramic

mainly there to prevent the smell of burning flesh
as one reaches in to adjust something or remove PLA booger!

Steel threaded section is heatbreak between
Aluminum heat block and cooled aluminum geared extruder.

? What extruder hotend is Lander using?

Build a FDM 3D printer, use a FDM 3D printer, use five or six different extruders
then ...
design your plutonium heated hotend with aerogel insulator!

Quote
cozmicray
The red stuff around heating element in pix
is Silicone rubber
NOT ceramic

Got fooled there.

Quote
cozmicray
? What extruder hotend is Lander using?

Bought a few of them, the cheap variety for begining. Of course I use what's available. But I never stop looking for alternatives.

Quote
cozmicray
aerogel insulator

Such a nice thing to have. I'm drooling for that stuff

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Not 10 cents, but cheapish
[www.ebay.co.uk]
Just need a micro version, cant be long before the spring in your pen example could do the trick.

Edited 1 time(s). Last edit at 11/11/2015 07:21AM by MechaBits.

If 1000W is 25.79 can 100W be 2.57?

It's simple, buy one of those, reverse engineer to have parts that can do 100-200W and make a prototype (board+coil). I wish I could understand the electronics

Edit: by the way from the picture I can see that there are two rows of the same components used to reach to 1000W, so make a board with half components and maybe even lower power ones and you'll be around the 10xMoney mark.

Edited 2 time(s). Last edit at 11/11/2015 09:04AM by realthor.

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I feel obliged to resurrect this thread as it has never faded off the back of my brain. I have just found this post, by accident, looking for something else of course. Here's an idea very similar to what i was expressing before regarding the "pen" induction-based hotend:

[sites.google.com]

This is the picture from the link:

.

We just need a collaborative effort between some electronics guys with guys specialized in manufacturing so that we end up with a cost-effective solution.

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Quote
cozmicray

Why not a Borosilicate (Pyrex) glass bushing/liner (essentially a tube) for the heat breaks with 4.1mm hole (those where the bowden tube go all the way until it touches the nozzle)?
Borosilicate (Pyrex) glass seems pretty close in thermal conductivity/insulation and should be good in strength/non sticking too.
Maybe not expensive either?
Why no one have done it already ..?


What do you think ?


(Hello everyone btw )

Edited 3 time(s). Last edit at 02/15/2019 04:49PM by townkat.

... read here - [reprap.org]



Edited 1 time(s). Last edit at 02/15/2019 02:34AM by VDX.

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--------
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Quote
townkat

Quote
cozmicray
[attachment 65585 Thermal_C.jpg]

Why not a Borosilicate (Pyrex) glass bushing/liner (essentially a tube) for the heat breaks with 4.1mm hole (those where the bowden tube go all the way until it touches the nozzle)?
Borosilicate (Pyrex) glass seems pretty close in thermal conductivity/insulation and should be good in strength/non sticking too.
Maybe not expensive either?
Why no one have done it already ..?


What do you think ?


(Hello everyone btw )

Why don't you do it and show the result ? You will have the answer.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

It's strange to see simple ideas stack up in such a complex way!

K.I.S.S!

Here is a really KISS solution:




Water-Cooled Hot-End
www.zatsit.fr

The idea is never going to go away, just needs someone with that light bulb moment to find that cheap and simple way of making a ceramic like heat break.

Maybe mold one using high temperature JB weld. The 1300C stuff (https://www.jbweld.com/products/j-b-extremeheat) would withstand any hot end .. this could be done by any non-doubting thomas I'm sure.

Maybe use the cheap ceramic fuse idea, put a 1.75mm drill bit (the smooth part) down the center (and firmly centered), then inject between the drill bit and the inner fuse wall with the above JB weld in order to create the 1.75mm channel you so desire ?

A standard ceramic mains fuse here in the UK is extremely strong, I just removed the two end caps off of a standard 13A one, It's I.D is 3.3mm .. maybe someone with the means could try some 3.3mm filament ? .. or do as above to reduce the inner diameter down to 1.75mm'ish ?

I've not yet used JB weld myself, so don't know what it's surface finish is like, but I soon will.

ps. maybe not JB Weld (it conducts heat I see), but maybe something like thermal insulation washers/collars or such like ..

[en-mx.misumi-ec.com]

Edited 2 time(s). Last edit at 02/15/2019 12:57PM by Pippy.

Can even get ready made ceramic tubes with 1.8mm I.D ..

[www.machiningceramicparts.com]

and porcelain tubes ..

[www.activeindustrialceramics.com]

Edited 1 time(s). Last edit at 02/15/2019 01:25PM by Pippy.

Quote
Pippy
The idea is never going to go away, just needs someone with that light bulb moment to find that cheap and simple way of making a ceramic like heat break.

Maybe mold one using high temperature JB weld. The 1300C stuff (https://www.jbweld.com/products/j-b-extremeheat) would withstand any hot end .. this could be done by any non-doubting thomas I'm sure.

Maybe use the cheap ceramic fuse idea, put a 1.75mm drill bit (the smooth part) down the center (and firmly centered), then inject between the drill bit and the inner fuse wall with the above JB weld in order to create the 1.75mm channel you so desire ?

A standard ceramic mains fuse here in the UK is extremely strong, I just removed the two end caps off of a standard 13A one, It's I.D is 3.3mm .. maybe someone with the means could try some 3.3mm filament ? .. or do as above to reduce the inner diameter down to 1.75mm'ish ?

I've not yet used JB weld myself, so don't know what it's surface finish is like, but I soon will.

ps. maybe not JB Weld (it conducts heat I see), but maybe something like thermal insulation washers/collars or such like ..

[en-mx.misumi-ec.com]

How about making it as all what is required is cheap, readily available ?

You will learn a lot from it and maybe ?

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

from the table, if the values are correct, thermal conductivity:
ceramic (Al2O3) -> 39
borosilicate glass -> 1.4

small thermal conductivity is essential in this situation.
that's why i am not too much for ceramics but more for glass.. (even standard glass should be good too) i think..

Edited 1 time(s). Last edit at 02/15/2019 02:16PM by townkat.

Quote
townkat
from the table, if the values are correct, thermal conductivity:
ceramic (Al2O3) -> 39
borosilicate glass -> 1.4

small thermal conductivity is essential in this situation.
that's why i am not too much for ceramics but more for glass.. (even standard glass should be good too) i think..

Wrong, high thermal conductivity is essential, to transfer heat from the heating element to the filament. But low thermal conductivity is good for a heat break.

Those figures show than borosilicate glass is around 30 times worse at conducting heat than alumina ceramic. This is a compelling reason to use alumina, not glass, because you need the heat to be conducted from the heating element to the filament inside the tube. Do the maths to work out the difference in temperature drop across the tube wall for both materials.

Many years ago I built waveguide CO2 lasers and faced a similar requirement, high thermal conductivity across the walls of a small tube. Glass was out. Alumina was OK and I built one laser using it; but I ended up using hexagonal boron nitride. Beryllium oxide ceramic would have been better but it is too toxic.

Edited 1 time(s). Last edit at 02/15/2019 04:51PM by dc42.

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Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].