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Hotend design question

Posted by TheBoy 
Hotend design question
December 23, 2017 01:55PM
Why do we use aluminum to transfer heat to our extruder head? If we wanted a more even heat transference shouldn't it be a metal that doesn't dissipate heat? Why not just put the heating rod in the extruder itself if it's already on a cnc the extra pocket shouldn't matter. It saves a step reduces production time and can still be sold for the same price.
Re: Hotend design question
December 23, 2017 06:11PM
Is your question in reference to hotends, extruders or both?

Hotend design is limited by size, production method, components (thermistor and heating element) as well as a plethora of other things. The heating block serves a very specific function and its hard to imagine an alternative.

As for material choice, the fact that aluminium dissipates heat is a desirable quality as it also means heat transfers from your heating element quickly. Copper would be the next best material here and I believe e3d now make a copper block.

As far as design goes though, I would love to see a more integrated system that combines extruder, hotend and accessories into one. The titan aero seems close but e3d havn't tackled a part cooling system yet that doesn't require awkward printed brackets. Mounting points in the hotend/extruder for accessories would be a huge bonus.
Re: Hotend design question
December 24, 2017 02:44AM
Quote
Origamib
Is your question in reference to hotends, extruders or both?

Hotend design is limited by size, production method, components (thermistor and heating element) as well as a plethora of other things. The heating block serves a very specific function and its hard to imagine an alternative.

As for material choice, the fact that aluminium dissipates heat is a desirable quality as it also means heat transfers from your heating element quickly. Copper would be the next best material here and I believe e3d now make a copper block.

As far as design goes though, I would love to see a more integrated system that combines extruder, hotend and accessories into one. The titan aero seems close but e3d havn't tackled a part cooling system yet that doesn't require awkward printed brackets. Mounting points in the hotend/extruder for accessories would be a huge bonus.

Yea hot end and extruder. See I was thinking that the aluminum will take heat and transfer it to the entire block; wouldnt it be better to create a directed hotspot similar to the properties of a thermic lance where the hot spot would be around the filaments path. I was thinking of a extruder with housing for heating rods and thermocouple. I think I will dabble with the idea. Just some brainstorming but what I was thinking of trying as to find the length of the hotend plus extruder, create pockets for the accessories like you said and have it be able to swap out by a few set screws.So that extruders are still replaceable you will just have a extra step in initial setup when replacing a extruder head.
Re: Hotend design question
December 24, 2017 03:10AM
You seem to be missing some basic information...

lets start with this break down of parts of a fairly standard hot end



Only the part that is in the heater block is heated, the rest is to stop the rest of it heating up
Re: Hotend design question
December 24, 2017 03:20AM
And look here at some history...

[reprap.org]
Re: Hotend design question
December 24, 2017 04:19AM
yea so still the same thing just different name. replace up to the thermal barrier.from the left side with one unit
Re: Hotend design question
December 24, 2017 08:09AM
So basically make a heater block+nozzle in one? Downsides are you can't change nozzles and cleaning or unclogging them becomes much harder. You'd also probably run into a few machining challenges. There could be advantages, care to throw a few into the ring?
Re: Hotend design question
December 24, 2017 10:20AM
Quote
TheBoy
yea so still the same thing just different name. replace up to the thermal barrier.from the left side with one unit

How about making one according to your ideas ? For a start, a drawing to avoid any confusion and eventually burning yourself or putting your house on fire ?


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
Re: Hotend design question
December 24, 2017 10:33AM
All the materials used have the properties that are needed.
Thermal barrier is from Stainless steel, because it doesn't conduct heat that well.
Heat block is from aluminum to get the energy from the heater to the nozzle and an accurate temperature reading.

I have a E3D hot and that uses this concept. and it never got blocked.
I can pull the filament out of the top when it is warm, and directly put new filament in. it never got blocked.
I just works really well.
But you can always try to improve it, But sometimes that is really difficult.

Edited 2 time(s). Last edit at 12/24/2017 10:34AM by amigob.


P3steel DXL, with Due/RADDS/Raps128 dual Wade's extruder
Re: Hotend design question
December 24, 2017 10:50AM
So you are proposing a hot point, instead of a hot block?

The advantage of having a heating block, is that the relatively large block of aluminium holds the heat well, meaning you can push more filament through before the block loses too much heat and causes extrusion issues. Basically, the bigger the block the more stable your heat output is. A smaller block, or thermal lance, would surely need a higher wattage heat cartridge to keep up, but then you introduce fire hazards. According to E3D, a 100 watt cartridge is enough to melt aluminium.

What are the advantages of a thermal lance that the traditional design does not have?
Re: Hotend design question
December 24, 2017 11:01AM
The hot ends on my Ormerod printer use combined nozzles/heat breaks made from stainless steel. They have been trouble-free. It still uses an aluminium block to connect the heater cartridge and thermistor to the nozzle.

The hot end made by deltaprintr wraps the heater around the nozzle, see [www.deltaprintr.com]. I haven't tried it, because they don't make a 24V version.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Hotend design question
December 24, 2017 02:35PM
Quote
Trakyan
So basically make a heater block+nozzle in one? Downsides are you can't change nozzles and cleaning or unclogging them becomes much harder. You'd also probably run into a few machining challenges. There could be advantages, care to throw a few into the ring?


The concept is to get more efficient heat transference through localizing the heat dissipation. Thats the end goal just more heat where we need it with less energy wasted. I was going to last night but I was drinking and my laptop died so i did other things lmao. But yea expect some files here soon. Just wanna enjoy the holidays.

Quote
Origamib
So you are proposing a hot point, instead of a hot block?

The advantage of having a heating block, is that the relatively large block of aluminium holds the heat well, meaning you can push more filament through before the block loses too much heat and causes extrusion issues. Basically, the bigger the block the more stable your heat output is. A smaller block, or thermal lance, would surely need a higher wattage heat cartridge to keep up, but then you introduce fire hazards. According to E3D, a 100 watt cartridge is enough to melt aluminium.

What are the advantages of a thermal lance that the traditional design does not have?

I have a few ideas i am wanting to try a induction coil and a ceramic spacer with an ID the diameter of the coil. To create a localized hotspot and get full coverage.

I was also considering slanting two heating rods to try and create a more focused heat near the tip. [imgur.com]

I want to produce a more efficient extruder head able to achieve higher temps with less current draw. Advantages would be backwards compatibility with anything the thermal bock could accept, production cuts adding one piece of tooling to a tool changer vs. having a entire other machine running producing a separate part. We are using the extrusion process lets try to get on the same level as industrial standards that's my end goal anyways.

Edited 1 time(s). Last edit at 12/24/2017 03:21PM by TheBoy.
Re: Hotend design question
December 24, 2017 03:42PM
and then you cant change nozzle size or replace the nozzle. They do wear out, quite quickly with filaments that effectively have abrasives in them.
Re: Hotend design question
December 24, 2017 04:52PM
and drill bits break. you are saying that because of tool changes you would prefer a less efficient system that you just screw in vs a more efficient system that you have to screw in and then attach components in initial setup. If more heat is transferred into the filament more efficiently wouldn't you consider it a better system?
Re: Hotend design question
December 24, 2017 05:00PM
The limiting factor when melting plastic is the time it takes heat to penetrate to the center of the filament. Moving the heat cartridge closer (or even into) the bore doesn't really change anything, because the filament was already in contact with hot metal to begin with.

You want even heat from every side, not a single small hot spot which will not have time to diffuse through the filament.

Inductive heating has the potential for tighter control of the block/nozzle temperature, but it doesn't really matter whether the nozzle is 220 or 222c. Plastic is not a good thermal conductor and it takes time to melt the center of the filament without burning the outside.

MIT just released a paper where the extruder is a quartz tube, and plastic is heated using an infrared laser which penetrates through the ABS filament, uniformly heating its entire volume.


Also efficiency isn't directly affected by where you apply the heat; it takes a fixed energy to heat a specific quantity of plastic. If you want to use less power, wrap the block in ceramic tape. Even when the block is un-insulated if you are in an enclosure you still get 100% efficiency since the "wasted" heat is warming the chamber.

Edited 1 time(s). Last edit at 12/24/2017 05:12PM by 691175002.
Re: Hotend design question
December 24, 2017 05:20PM
What you want to produce looks magnificent, innovative, promising and would sell like hot cakes but again, make a PROPER drawing and even better a prototype.

"The proof of the pudding is in the eating" but so far I don't see a proper kitchen, cookware, ingredients not even a recipe to make this delicious pudding !


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
Re: Hotend design question
December 24, 2017 09:39PM
An induction heating electronics is not that simple, and expensive.

Extruder and hot end are a high pressure pump.

Taking polymer from solid, to plastic, to liquid
and then pressed out a small nozzle

The heating zone has to be a specific size
to provide a melt zone and pressed out with solid
filament as a piston.

What is the deal with making it more efficient
?Battery powered printer?
Takes a lot of thermal energy to melt meters of polymer
into your latest printed project

confused smiley
Re: Hotend design question
December 24, 2017 10:04PM
Induction heating of hot ends has been done....

[forums.reprap.org]

It didnt take off.... to complicated for not enough gain.
Re: Hotend design question
December 25, 2017 02:56PM
Following from @TheBoy's proposal; imagine putting the nozzle thread inside the heater cartridge. Have a (say) 10mm outside diameter, 6mm inside diameter, 4mm tall tubular heating element with an M6 thread inside for the nozzle (i.e. the nozzle threads extend right through the heater doughnut). Make the heater doughnut out of some material with good thermal mass (metal?) for temperature stability, although fast-responding PID control of the temperature may be good enough? (Not quite sure how to get the nichrome wire and thermistor into it, but maybe someone has some ideas?). Thread the outside of the heater, to screw into a carrier made of a thermal insulator (ceramic or epoxy?), including the top of the tube, leaving a 2mm diameter hole for the filament to enter. All the energy goes into heating the nozzle and the filament inside it, and little escapes from the carrier... no need for a heatbreak, heatsink, or fan.



Carrier is grey, heater blue, nozzle yellow, filament red.
Re: Hotend design question
December 25, 2017 07:50PM
Quote
dc42
The hot ends on my Ormerod printer use combined nozzles/heat breaks made from stainless steel. They have been trouble-free. It still uses an aluminium block to connect the heater cartridge and thermistor to the nozzle.

The hot end made by deltaprintr wraps the heater around the nozzle, see [www.deltaprintr.com]. I haven't tried it, because they don't make a 24V version.

I've got a deltaprintr mini hotend and it works great, it's a bit like the design above but much smaller with a ceramic heater around the nozzle. So it heats quite evenly, but it's thermal capacity is smaller than an e3d block, even though it's heater is equally powerful for its small size sudden changes in demand at higher speeds cause it trouble as the Pid algorithm isn't predicting upcoming higher demand and beginning to increase current to the heater it lags behind somewhat,but as an alternative design it's one of the more plausible ones out there.

[www.deltaprintr.com]

Edited 1 time(s). Last edit at 12/25/2017 07:51PM by DjDemonD.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Hotend design question
December 26, 2017 01:58AM
To surround the nozzle with the heating element like drawn above (although this "design" wouldn't work as it misses the key point, the cold/hot transition zone) is not new at all.
In fact it is the first one because it is obvious way to do it !
3D pen hot end are still built that way.
[www.aliexpress.com]

The novel idea has been to use a separate heating element in the current tube form you could easily install in a block the size and material you want. Same with the separate threaded nozzle and heatbreak.
A matter of flexibility, cost, ease of manufacture, maintenance. It is not the absolute best but the best compromise !

I make my own hot ends. I dismissed the induction heating too (great to heat treat steel and silver solder my heatbreak though).

Everything is great on a sheet of paper and even greater on a computer animation. Just that reality sucks ! smiling smiley

Edited 3 time(s). Last edit at 12/26/2017 08:23AM by MKSA.


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
Re: Hotend design question
December 26, 2017 04:20AM
The other thing I think the mini hotend gets right is the thermistor is retained by a sock in a recess in the side of the nozzle itself, so you are measuring nozzle temp, not heater block temp.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Hotend design question
December 26, 2017 03:01PM
Economics
What is cheaply available Now
What is vaporware?



confused smiley
Re: Hotend design question
December 28, 2017 04:58PM
This is very valuable information sorry i hav been dragging my feet. I actually stumbled on the torus design as well (and was just about to make a post about it lmao). I believe inductive magnetism through torodial coils could be used with powder deposition along with two separate induced fields to create a force capable of fusing disimilar metals and leading the way for addman in transmutational metallurgy. But we aren't concerned with that part of my extruder research xD what we as a community want is a better, simpler more versatile design. And I believe this thread will help lead to more out of the box concepts.

Quote
frankvdh
Following from @TheBoy's proposal; imagine putting the nozzle thread inside the heater cartridge. Have a (say) 10mm outside diameter, 6mm inside diameter, 4mm tall tubular heating element with an M6 thread inside for the nozzle (i.e. the nozzle threads extend right through the heater doughnut). Make the heater doughnut out of some material with good thermal mass (metal?) for temperature stability, although fast-responding PID control of the temperature may be good enough? (Not quite sure how to get the nichrome wire and thermistor into it, but maybe someone has some ideas?). Thread the outside of the heater, to screw into a carrier made of a thermal insulator (ceramic or epoxy?), including the top of the tube, leaving a 2mm diameter hole for the filament to enter. All the energy goes into heating the nozzle and the filament inside it, and little escapes from the carrier... no need for a heatbreak, heatsink, or fan.

[attachment 100871 Screenshotfrom2017-12-2608-49-30.png]
[attachment 100872 Screenshotfrom2017-12-2608-52-53.png]
Carrier is grey, heater blue, nozzle yellow, filament red.

This is similar to the idea i had I was considering adding a sleve so we could add any hotend gen we wanted to the top we just need to conversion sleeve; but now we are falling way from machine simplicity for a more friendly user interface
Re: Hotend design question
December 29, 2017 09:22AM
Any prototype soon ?


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
Re: Hotend design question
January 04, 2018 02:53AM
Ah DJ?
A quick question about the mini hot end.
How is the nozzle attached to the rest of the hotend? It has an M4 thread, right? But the ceramic ring has an internal diameter of 5mm or so.
Same for the heat break. Are they simply glued in? No, they are selling nozzles.


Lykle
________________________________________________

Co-creator of the Zesty Nimble, worlds lightest Direct Drive extruder.
[zesty.tech]
Re: Hotend design question
January 04, 2018 03:03AM
Hi good question the nozzle is definitely removable but I haven't had cause to take it apart yet partly because it's quite reliable and partly because it's currently attached to a printer that I don't use very often however M4 thread does ring a bell I know that the nozzles are not compatible with e3d as I would really like to swap for a smaller nozzle than 0.4 but none is available as yet apologies for no punctuation I'm dictating this


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: Hotend design question
January 06, 2018 03:28PM
Quote
TheBoy
Why do we use aluminum to transfer heat to our extruder head? If we wanted a more even heat transference shouldn't it be a metal that doesn't dissipate heat? Why not just put the heating rod in the extruder itself if it's already on a cnc the extra pocket shouldn't matter. It saves a step reduces production time and can still be sold for the same price.

Sounds like you are thinking along the lines of an injection-molding style self-heated "hot runner nozzle" concept. You could google that to see what the ins and outs of it are. Even a non-cartridge soldering-iron style helical heater concept may work.

I would not be stoked about an integrated nozzle, but I am on-board with the surround heating element. The mini delta hot ends touch on it, but I hope to grab a bunch of cheap off the shelf examples and run some experiments in the future. If you are interested, search for "band heating element" or "enclosed nozzle heater". Even ceramic helical elements for high-current vape pens may be usable.

A tradeoff -- as was mentioned -- is that you lose the thermal mass of the aluminum block, but spinning a cylinder heat 'block' on a lathe for an insulated surround heater is not unreasonable.

Induction heating is something I also hope to work with in the new year, and that would fall somewhat inline with your brainstorm since you could essentially heat a ferritic nozzle directly rather than indirectly through a thermal mass+cartridge. I worked for a while as a contractor to design and build control equipment to an induction smelting company, so I have a nagging desire to see that concept through with a small breakout board regardless of previous attempts.
Re: Hotend design question
January 06, 2018 04:27PM
@AletheianAlax,
This has been tried several times with varying degrees of success. My try of about 6 months ago, documented a bit in [forums.reprap.org] but in the end I couldn't get the thermal break short enough or the weight light enough (or the cost low enough) but I could see that it only needed a hop, skip and jump to be there. If you do get anywhere with this please keep us up to date as I think it is something that most of us think has potential.

Mike
Re: Hotend design question
January 06, 2018 04:34PM
Quote
AletheianAlex
Quote
TheBoy
Why do we use aluminum to transfer heat to our extruder head? If we wanted a more even heat transference shouldn't it be a metal that doesn't dissipate heat? Why not just put the heating rod in the extruder itself if it's already on a cnc the extra pocket shouldn't matter. It saves a step reduces production time and can still be sold for the same price.

Sounds like you are thinking along the lines of an injection-molding style self-heated "hot runner nozzle" concept. You could google that to see what the ins and outs of it are. Even a non-cartridge soldering-iron style helical heater concept may work.

I would not be stoked about an integrated nozzle, but I am on-board with the surround heating element. The mini delta hot ends touch on it, but I hope to grab a bunch of cheap off the shelf examples and run some experiments in the future. If you are interested, search for "band heating element" or "enclosed nozzle heater". Even ceramic helical elements for high-current vape pens may be usable.

A tradeoff -- as was mentioned -- is that you lose the thermal mass of the aluminum block, but spinning a cylinder heat 'block' on a lathe for an insulated surround heater is not unreasonable.

Induction heating is something I also hope to work with in the new year, and that would fall somewhat inline with your brainstorm since you could essentially heat a ferritic nozzle directly rather than indirectly through a thermal mass+cartridge. I worked for a while as a contractor to design and build control equipment to an induction smelting company, so I have a nagging desire to see that concept through with a small breakout board regardless of previous attempts.

Sounds very interesting. You should team up to make a prototype.


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