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Ideal hot end design for PLA

Posted by Pawan 
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Pawan
Ideal hot end design for PLA
April 29, 2016 01:27PM
Suggest a hot end design for only PLA printer which can be made much cheaper than E3D all metal hot end but works equally effective.
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etfrench
Re: Ideal hot end design for PLA
April 29, 2016 01:35PM
E3D clones are <$10. How much cheaper do you need it?
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JamesK
Re: Ideal hot end design for PLA
April 29, 2016 01:46PM
Quote
etfrench
E3D clones are <$10. How much cheaper do you need it?

Except the clones may or may not have an ideal design.

If the hotend is only going to be used for pla then I don't think you can beat taking a ptfe liner all the way down to meet the nozzle. That way friction is as low as possible and there are no joints in the critical area above the transition zone.

From E3Ds website for the Lite6, this is exactly what I would do with the liner:



However, for 'ideal' I would still use stainless steel only for the heat-break, and put an aluminum heat-sink on top of it.

Edited 1 time(s). Last edit at 04/29/2016 01:52PM by JamesK.
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Pawan
Re: Ideal hot end design for PLA
April 29, 2016 01:58PM
How would a heater block plus nozzle machined from one block of brass perform in comparison to aluminium block? Wouldn't the PTFE liner spoil if put such close to the nozzle like E3D lite?
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JamesK
Re: Ideal hot end design for PLA
April 29, 2016 02:06PM
Quote
Pawan
How would a heater block plus nozzle machined from one block of brass perform in comparison to aluminium block?

I would expect it to work fine, but brass is much more expensive than aluminum, so it would be an expensive choice. The nozzles also wear and sometimes get blocked, so it's best to treat them as consumables that will need to be replaced from time to time. That's more affordable if the nozzle is separate from the block. (But also check out Srek's merlin hot end that uses stainless steel nozzles - I suspect they suffer much less wear).

Quote

Wouldn't the PTFE liner spoil if put such close to the nozzle like E3D lite?

Not at PLA temperatures, and in my experience I've seen no problems with PTFE at ABS and nylon temps either - up to about 265C. My current hot-ends don't take the liner into the heater block, but I printed ABS and nylon for several months with MK8 hot-ends which do have the PTFE up to the nozzle. Other people have reported problems with the liner though, so maybe I was just lucky.
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Pawan
Re: Ideal hot end design for PLA
April 29, 2016 02:12PM
Why do people choose brass for the nozzle? Aluminium alloys or SS do not serve the purpose?
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JamesK
Re: Ideal hot end design for PLA
April 29, 2016 02:16PM
Quote
Pawan
Why do people choose brass for the nozzle? Aluminium alloys or SS do not serve the purpose?

Brass has a good combination of thermal conductivity and hardness. Aluminum has better conductivity but isn't as hard so will wear faster. Some people use steel nozzles which are harder wearing than brass, but have poorer thermal conductivity.
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Pawan
Re: Ideal hot end design for PLA
April 29, 2016 02:25PM
What about copper nozzle? Has anyone tried?
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leadinglights
Re: Ideal hot end design for PLA
April 29, 2016 02:39PM
I have always made my heater blocks out of copper but I wouldn't use it for a nozzle as it tends to be too grabby - trying to drill holes less than 0.5mm would break too many drills. Aluminium is slightly better but both brass and stainless steel are pretty well behaved by comparison.

Mike
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JamesK
Re: Ideal hot end design for PLA
April 29, 2016 02:48PM
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leadinglights
I have always made my heater blocks out of copper but I wouldn't use it for a nozzle as it tends to be too grabby - trying to drill holes less than 0.5mm would break too many drills. Aluminium is slightly better but both brass and stainless steel are pretty well behaved by comparison.

Nice! With a thermal conductivity roughly twice that of aluminium, copper makes sense for the heat block but it's a bit pricey for me. I have a little brass in my stock, but no copper at all. I love turning brass. Aluminium is ok, but I don't enjoy stainless or even the mild steels for that matter. I have some leaded steel that does turn quite nicely though. As an aside, a machinist friend of mine tells me that the ultimate for "nice on the lathe" is pure gold. He actually made a set of gold standards! I wouldn't recommend it for a printer nozzle though.
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leadinglights
Re: Ideal hot end design for PLA
April 29, 2016 03:05PM
True, but the world conspires to stop us using the best materials. Conductivities of materials from Wikipedia ( [en.wikipedia.org] )

Diamond, Natural 2200
Copper, pure 483
Aluminium 236 ( at 273K )
Brass Cu 63% 125
Steel, Stainless 16.3

But then I guess diamond is a bit tricky to machine.

Mike
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Pawan
Re: Ideal hot end design for PLA
April 29, 2016 03:17PM
I think aluminium is the best material for nozzle...It has both twice the thermal conductivity and twice the specific heat capacity of brass. Is there any way to reduce wear like by increasing material around the nozzle hole or some coating? Any Al alloy wear resistant to an extent?
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Srek
Re: Ideal hot end design for PLA
April 29, 2016 03:30PM
Aluminum is to soft. You could electroplate it, but afaik the thermal conductivity isworse then.
For a nozzle stainless steel and brass are realy the two best options.

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
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ggherbaz
Re: Ideal hot end design for PLA
April 29, 2016 03:43PM
For PLA only, you can get rid of the aluminum cooler fins and the stainless steel heat brake pipe.

If you properly insulate the top of the heater block or the whole thing better with porcelain, quartz glass or any other high temp material you can use a theaded press fitting on the PTFE tube and bolted straight into the heater block. The fitting will work as your thermal separator between the aluminum block and the PTFE liner and the insulator will prevent the heat from going up to the liner, the air passing through it will be sufficient to cool it of.
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Pawan
Re: Ideal hot end design for PLA
April 29, 2016 03:51PM
That sounds like a nice idea ggherbaz. IS there any existing hot end of this type?
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Srek
Re: Ideal hot end design for PLA
April 29, 2016 04:01PM
Quote
ggherbaz
For PLA only, you can get rid of the aluminum cooler fins and the stainless steel heat brake pipe.

If you properly insulate the top of the heater block or the whole thing better with porcelain, quartz glass or any other high temp material you can use a theaded press fitting on the PTFE tube and bolted straight into the heater block. The fitting will work as your thermal separator between the aluminum block and the PTFE liner and the insulator will prevent the heat from going up to the liner, the air passing through it will be sufficient to cool it of.
Have you tried this? It goes against my experience.

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
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reifsnyderb
Re: Ideal hot end design for PLA
April 29, 2016 04:03PM
Hello,

A genuine J-Head hot-end (made with PEEK, PTFE, and brass) is perfect for printing PLA. In some cases, a cooling fan isn't even required. It prints PLA fast, doesn't jam, and lasts for a long, long time.

[reprap.org]

Aluminum can be used primarily for weight reduction. If 2024 or 7075 aluminum is used, it is not soft like the common 6061. However, 7075 is roughly as expensive as brass.

Brass works perfectly, holds up for the application, and machines easy.

As far as the price is concerned, Genuine J-Head hot-ends are $40.00 each in quantities of 10 or more. Chinese clones exist in huge quantities; but, they aren't made to the proper specifications and are prone to failure.

Best Regards,

Brian
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ggherbaz
Re: Ideal hot end design for PLA
April 29, 2016 04:09PM
Srek,

I have not yet, but have the parts been made. The only data I have is coming from computer animated thermal graphics, I assume that I will have some real life data in a few weeks.
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Pawan
Re: Ideal hot end design for PLA
May 01, 2016 06:52AM
ggherbaz, do share your data in this thread when you have it.

PTFE glass transition temperature is 115C, so how can it be brought close to the heater block/nozzle whose temperature is above 200C?

Edited 1 time(s). Last edit at 05/01/2016 06:52AM by Pawan.
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Srek
Re: Ideal hot end design for PLA
May 01, 2016 07:20AM
PTFE getting soft is not a hindrance. There is always a temperature gradient from the heated zone to the beginning of the PTFE tube. One of the key tasks when designing a hotend ist to make the gradient as steep as possible and keeping the PTFE from deforming.

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
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DjDemonD
Re: Ideal hot end design for PLA
May 01, 2016 07:02PM
Thermal conductivity of Tungsten is 173 W/(m·K) and it won't wear away very quickly at all, not sure it will turn on a lathe though.
I wonder if these guys will get this off the ground? [dddmaterial.com]

Edited 1 time(s). Last edit at 05/01/2016 07:02PM by DjDemonD.

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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JamesK
Re: Ideal hot end design for PLA
May 01, 2016 07:18PM
Quote
DjDemonD
Thermal conductivity of Tungsten is 173 W/(m·K) and it won't wear away very quickly at all, not sure it will turn on a lathe though.
I wonder if these guys will get this off the ground? [dddmaterial.com]

Doesn't look like it, the kickstarter only made half the target amount. It looks like it would be a good nozzle, but I'm not sure the advantages justify the cost differential compared to 'disposable' brass nozzles that, when all is said and done, work pretty well.
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DjDemonD
Re: Ideal hot end design for PLA
May 01, 2016 07:22PM
Agreed. But putting all that pragmatism aside though, tungsten nozzles look cool (probably less so when covered in burnt filament).

Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions
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Pawan
Re: Ideal hot end design for PLA
May 02, 2016 12:12PM
Srek, E3D Lite has PTFE tube half way into the heater block and also touches the nozzle. Even with all gradient the temperature must definitely cross 220C. How come its working at that temperature?
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Srek
Re: Ideal hot end design for PLA
May 02, 2016 12:30PM
Quote
Pawan
Srek, E3D Lite has PTFE tube half way into the heater block and also touches the nozzle. Even with all gradient the temperature must definitely cross 220C. How come its working at that temperature?
Ask E3D winking smiley
I don't know, i did not find it neccessary to go this deep and i still can't see any advantage.
Either way, PTFE stay stable, if you don't apply forces to deform it, for higher temperatures. The melting point of PTFE is above 300°C, until then it just becomes softer.
This is one reason why in the Merlin i use a Teflon inliner with a M6 thread, it has way more grip that way and is not under much pressure over its length.

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
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Pawan
Re: Ideal hot end design for PLA
May 02, 2016 12:44PM
Hey Srek, can you tell me more about ur Merlin hot end? Any blogpost explaining the design or any picture/section view?
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Srek
Re: Ideal hot end design for PLA
May 02, 2016 12:48PM
Check my signature

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
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Pawan
Re: Ideal hot end design for PLA
May 02, 2016 12:59PM
Its good. You use Merlin for only PLA or even ABS. how often does it jam when using PLA?
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Srek
Re: Ideal hot end design for PLA
May 02, 2016 01:09PM
I rarely print PLA but mostly ABS. So far i was able to print all filaments i tried reliably, including PC, HIPS, Nylon and various elastic materials. Also all materials with additives like wood, copper etc print nice, though i only print them with a 0.5mm nozzle.
Many others use it for PLA though.

Edited 1 time(s). Last edit at 05/02/2016 01:10PM by Srek.

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
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Pawan
Re: Ideal hot end design for PLA
May 02, 2016 01:32PM
Srek, do you use fan on merlin? DO the airbrush nozzles directly available in market last long or do you replace them periodically?
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