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Ideas for High Temperature Extruder (printing Polycarbonate)

Posted by RP Iron Man 
Ideas for High Temperature Extruder (printing Polycarbonate)
April 27, 2013 07:56PM
Hey guys,

I have been brainstorming ideas for a high temperature extruder that would be capable of printing higher temperature thermoplastics (especially Polycarbonate). Since Polycarbonate can be extruded from 280C - 320C, I was going to design the hot end to be able to handle up to 350C/400C.

From my experience and based on what I have read on the forums, hot end designs that use PTFE or PEEK as thermal insulators cannot withstand the temperatures required for PC. (The melting points of both PTFE and PEEK are under 350C, and PTFE starts to deteriorate at temps above 260C.) The alternative to the PTFE/PEEK thermal barrier is the all-metal extruder design. While this eliminates the danger of melted PTFE insulators, it creates a bunch of other issues (heat creep, added fans, increased number of CNC machined parts), so ultimately, it is not the ideal solution. What we really need is a rigid thermal insulating material that can withstand temps of 350C for long periods of time. Why not MDF?

I am not sure if anyone has tested this before, but it seems like the best solution to this problem. The thermal conductivity of MDF is 0.05W/mk, compared to 0.25W/mk for PTFE/PEEK! Additionally, MDF shows very little deformation at high temperatures, and since it is made of wood fibres, it will not melt smiling smiley At 1/5 the thermal conductivity of PTFE and with it's consistent rigidity, MDF seems like it would be the perfect candidate for a thermal barrier in a high temperature extruder. I have not tested this yet, but I was wondering if anyone else had. Is there some unappealing property of MDF that I am overlooking? This could also cut down on the number of necessary CNC machined parts and junctions where the parts meet by replacing the conventional PTFE tube and brass barrel combo with a single MDF part. I was thinking that you could have the drive gear push the filament directly into the MDF insulator, which could have an M6 external thread on the bottom end with the brass nozzle/ heater block attached to it. Since the filament would feed directly from the "MDF barrel/insulator" into the brass nozzle, the melt zone could be reduced to about 4 to 10mm (depending on the nozzle design). This would really reduce the chances of the hot end clogging (right?). Sorry, I am explaining a lot of things in words...I wish I had of drawing of this -__-

While there do seem like a lot of advantages to using MDF as an insulator/barrel, I can imagine that there are also many drawbacks. For one, MDF is not very durable so it may wear away quickly with the filament constantly passing though it. Also, the external threading may not work out as the brass nozzle threads may cut right through the MDF threads. I was also thinking that MDF is not nearly as smooth as PTFE, so the added friction may significantly impede the movement of filament through the "barrel". Additionally, MDF quickly absorbs moisture from the air, which may block the passage of filament through the insulator (though I think the high temps of the hot end would eliminate this problem). Lastly, there could be a problem of hot plastic sticking to the inside of the MDF barrel and jamming the hot end (though I am not sure of how well different thermoplastics would stick to MDF...). Anyway, that is all I could come up with in terms of using MDF as a thermal insulator. What do you guys think??? I am not too sure about anything that I just mentioned, its all very theoretical, so let me know if I am completely wrong smiling smiley Are there any other thermal insulators that would be better suited for the higher temps required for PC? I am trying to avoid the all-metal hot end at all costs. It seems like waaayyyyyy to much trouble than it's worth.

Ok, so other than the thermal insulation issue, there is the problem of heating the nozzle to 320+C. Would I be able to achieve this with 2 standard 6.8OHM heat resistors (Nophead?). I haven't tried this because I don't have a spare hot end and don't want to melt my PTFE insulator smiling smiley

Also, a more significant problem would be the thermistor. The standard Honeywell NTC thermistor is only rated up to 300C, so going up to 320C or 350C may be risky (can someone verify this?). Most of the thermistors that are commonly used are rated at 300C. Does anyone know of a cheap thermistor that can handle up to 350C or 400C?

That's all I could come up with for now. I was thinking that the RepRap community really needs a stable high temp hot end design, so we can start experimenting with higher temperature thermoplastics. I was focused on Polycarbonate because it seems like the next step above ABS. Its has an extremely high impact strength, it is resistant to bending and it is very clear. It is also used as "bullet-proof glass"!

Also, initially I was looking at the possibility of extruding PTFE, but I discovered that it undergoes pyrolysis at above 260C... It may end up forming a charred mess/carcinogens before it reaches its melting point (anyone tested this?). It would be really cool if we could use this extruder to reprap PTFE thermal barriers for other printers!

Are there any other thermoplastics besides PC that could be extruded with higher temp capabilities? How about Nylon?

Jeez, looks like I wrote an essay! I'll stop now before the mods ban me for spamming the forums smiling smiley Let me know what you guys think!


Re: Ideas for High Temperature Extruder (printing Polycarbonate)
April 28, 2013 12:15AM
Ok, so I managed to find a spare heat block and did some tests and it doesn't look like MDF will cut it as a thermal insulator sad smiley While it performs well around heat bed temps, it starts smoking at 200C and by 350C it is billowing toxic smoke. Conclusion: MDF is not safe at high temps. Its a pity, MDF is a great insulator (even at 350C, I could touch the small MDF piece without burning myself). It could probably be used in the same way that PTFE/PEEK are used in conventional hot ends. I guess the all-metal/fan cooled design is the only way to go sad smiley

Also, in case anyone was curious, Using two 6.8ohm resistors at 12V, the temperature of the brass block reached 350C in under 2 minutes easy, so there is definitely no problem with using the standard wire-wound resistors as the heating element for Polycarbonate extrusion. However, I am still not sure about the Honeywell thermistor. While it survived at 350C I'm not sure how it would perform when operating at that temperature for long periods of time. It would probably be better to use a thermistor that is rated for the higher temperatures.

Does anyone know of an alternative thermistor that can handle up to 400C?
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
April 28, 2013 04:32AM
I think you need to use a thermocouple above 300C. I haven't seen any thermistors that go beyond that.

Re: Ideas for High Temperature Extruder (printing Polycarbonate)
April 28, 2013 03:10PM
... I'm using PT100 sensors with industrial temp-controllers or in special applications with C51-controllers from room-temp to 800C ... but you'll need 16Bit-ADC's, as you'll need more resolution for measuring and PID ...

Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
May 11, 2013 03:37AM
Hi Victor,
How can i use Pt100 to connect it to a rapms 1.4 for my 3d printer?
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
May 11, 2013 02:24PM
... you'll need an OP or similar for adjusting a defined range to 0-5V, so the DAC's can read them. In my modules the PT100 are sensed by a current-loop circuit and the resolutions is around 16bits, so much higher accuracy and tempreature range (-60 to +800 degC) than with Arduino ...

Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
May 17, 2013 02:18PM
Hi Vickor,
can you please explain me a little simpler? i am a newbie in Reprap, just start to my first one, I am using Ramps 1.4, so how can i connect thermocouples to my RAPS board? (I dont want use thermistors), what changes in hordware and in softwares? can some on eexmpain to me simply and efficent?
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
May 17, 2013 04:31PM
... here is some info for electronics, datasheets and calculations for a thermocouple sensor: [www.reprap.org]

I'm using the PT100's with different electronics (16Bit and 24Bit-ADC's), so not really helpfull for you ...

Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
May 28, 2013 05:26PM
Do you think the mdf could be treated with some high temp epoxy to keep moisture out and extend its life as an insulator? I'm curious since it would be nice to have a hotend that can handle polycarbonate and the higher temp print range for nylon(currently running a budaschnozzle 1.3 and want to play w/ polycarb) without a PEEK insulator meltdown
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
May 30, 2013 12:45AM
RP Iron Man Wrote:
> Does anyone know of an alternative thermistor that
> can handle up to 400C?

Operating Temperature:

Possible to use up to 400 deg.C
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
July 05, 2013 06:27AM
Anything new about printing with polycarbonate?

How about a ceramic hot-end for that?
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
July 08, 2013 04:08PM
Hm. No need for a special hotend, as far as I understand now.

Seems that 300°C at 120mm/s works. An active cooled hotend should make it, I guess?

Anybody with more experience in printing PC?
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
July 12, 2013 07:33AM
I use a design of hot end that should work at 300 degrees - a semi-all-metal with a PTFE sleeve which extends only as far as the point where the metal is at about 80 degrees. The nozzle is made of stainless steel with a thickness of only 1mm between the heated block and the melt chamber. A heatink holds the temperature where the incoming filament enters to less than 40 degrees.

Photo (CAD section 3D) below is a section of the part built 3rd iteration of the design using cuttlefish bone thermal insulators - previous ones used PEEK boxes enclosing the heated block.


Edited 1 time(s). Last edit at 07/12/2013 07:34AM by leadinglights.
open | download - NewExtruder_AirRing_Bottom_Section2.jpg (66.4 KB)
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
July 18, 2013 03:23PM
E3D Online has an all metal design that should be able to reach those temperatures for extruding polycarbonate quite easily. Richrap has done this (without using the E3D) and posted it on his blog.
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
July 19, 2013 12:45PM
Hi Mike,

Your 3D model looks nice, but I'm worried about how you are going to make them.
There are many thin walls, formed metals, machined parts, welded sheet metal on your design. What kind of tooling do you have?
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
July 22, 2013 04:05AM
Hi woodencase01,

The reason that I put that on this forum was to point out that careful thermal profileing could give both a shortish melt chamber and PTFE lining on most of the filament path and have that up to high temperatures without a true all metal hot end.

I admit that the model in the CAD is a little over the top, but it is just an exploration of some techniques - in this case, rapid cooling of the extrusion via the annular vent. Results of this still in the air, but I will report to the forum when, if and how successful/disasterous they are.

The sheet metal work is fairly simple, being just 0.3mm brass sheet cut with snips, bent over wood forms and soldered. The heatsink is a bit of self indulgence as I accidentally made the first one of these three itterations ago - and it was so damn pretty that i am now cursed to repeat it endlessly.


Edited 1 time(s). Last edit at 07/22/2013 04:28AM by leadinglights.
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
July 22, 2013 09:57PM
Looking forward to see how it will look!
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
July 25, 2013 10:31AM
Sanjay here from E3D Online - we can and do print with polycarbonate without any issues on the E3D v5. 300C works very nicely, but you can extrude a bit lower.

The thermistor we supply with the kit is rated to 300C - but we have gone a bit higher without much issue. 320C or so, but it's impossible to know if that is really the true temperatures being achieved as we were obviously operating beyond the spec of the thermistor.

We used PC from ultimachine in the US. It extrudes beautifully, very clean and glassy, inter-layer adhesion is absurdly strong, printed parts are also shockingly strong. A printed test strip 3mm high in Z and 20*50 in XY, with 3 solid top/bottom layers and 3 perimeters was impossible for me to break with my bare hands.

I only printed some small parts (60mm*20mm in XY plane, and 30mm tall) for a specific purpose/customer that needed the strength, I used Polycarbonate-Juice which is just like ABS-Juice but made with PC and Dichloromethane instead of ABS and Acetone. Small brim generated in slic3r, 120C bed temp, kapton surface. No warp experienced on this particular part - but I haven't done any further experimentation beyond the part in question.

I Design/Sell all-metal hotends. My company is called e3d-online - you can buy at [www.e3d-online.com]
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
July 25, 2013 09:24PM
Sanjay, you are doing a wonderful job. Your hot end design is great and I might be interesting in buying one some day.
I'm new to hot end design, but there is quite a challenge! Looking forward to see more of your nice work!
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
August 06, 2013 08:21AM
stainless steel or better titanium alloy work great as heat barrier as long as you keep the walls thin. or make bigger heat sink - but energy goes into space sad smiley


and works fine: [www.youtube.com]

it's pretty straight forward but i will post some better documentation along with other golemD files.

soon a polish forum friend should make some test on a ABS carriage printer with aluminum plate as interface.
Ideas for High Temperature Extruder (printing Peek
September 06, 2014 05:08PM
Anybody with more experience in printing Peek ?
Re: Ideas for High Temperature Extruder (printing Polycarbonate)
December 17, 2014 01:04AM
I was part of a working group that tried PEEK. Does not stick to the bed.

What you need is a print head with a dramatic temp change from hot to cold state. Plastic is in 3 states for the sake of discussion.

Solid filament, rubbery sticky, and liquid. You want the middle state to be as small as possible. Which means active cooling. The solid filament acts like a plunger in the filament guide if designed right. The cold end needs to stay cold and the hot end stay hot. I'm getting this change with only a few mm between using water cooling.


I tried air cooling, but the higher I go, the air cooling is not able to remove the heat in the right spot fast enough. Even with a e3ad and a 2 amp fan.

When reaching in the 500c range I found that I had to seriously increase the capacity of the heat sink even with water cooling.
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