What do you think about Dragon Hotend

arhi

@deckingman said in What do you think about Dragon Hotend:

@arhi PLA doesn't "cook" but what it does do is hydrolyse. That is to say, the longer it is held at print temperature, the less viscous (more "runny") it becomes.

Good to know, it's much easier to handle "empty" than "charred" nozzle :). I had nozzles that I had to redrill with a larger drill as it was impossible to clean up carbonised ABS.

I haven't connected my RPI yet but I'm told that it would be possible to do "time based" purging using the SBC (something to do with a python program using the API).

I'm waiting for that to become "a thing", especially the support for duet2+sbc before I invest some time to see what can be actually done with it. Slowly going trough Danal's work on the library and thinking about redoing (in go most probably, 'cause I need a reason to become more proficient in go) his library and porting the plugins I'm used to on octoprint to this new platform.. but for now I'm just patiently waiting to see where it all leads as for now I don't see a reason to go duet3 way and my bunch of duet2 boards so far don't know how to communicate with SBC.

theruttmeister

@arhi said in What do you think about Dragon Hotend:

@deckingman said in What do you think about Dragon Hotend:

@arhi This is getting off topic I know

Maybe @Phaedrux can rip the off-topic part of our discussion into a new topic about all metal hotends - pros/cons/history/ideas... might be useful discussion

Yes. There's an awful lot of people who are still building things like that dragon hotend, and have clearly never seen the early dev work done by NopHead.

And the dragon hotend?
Will suck with PLA. Heatsink is waaaaay too small.
It actually looks like the hotend Prusa was waving around about 7 or 8 years ago that he never got to work.

but I'm beginning to think that an all metal mixing hot end just isn't possible. My latest design iteration will confirm that (if I've managed to cure all the leaks). The reason why I'm beginning to believe that is because when one has multiple inputs, inevitably some of those filaments will not be moving forward at all for maybe hours.

That is the reason I never wanted to use all those "two nozzles single heater" nor "two input single nozzle" solutions popping up since day one. The major reason is that I'd be going either "main+support" or "hard+soft" combo of materials so 99% of the time only one will be printed while the other material will 99% of the time sit still and cook... not to mention when they require different temps (like TPU/PVA + ABS/PETG/HIPS/ASA combo). That is also why I never seriously looked at the diamond as the "color" aspect is fairly irrelevant for what I print (if it needs color it will be post-processed).

Regardless of how efficient the heat break is, it is inevitable that the filament itself will conduct some heat. Maybe a periodic purge of the "unused" filaments might help.

Based on the work I've done, thermal creep isn't the main issue. At least not if your heatsinks are large enough. But all the other things are problems.

IMHO the "purge" should work. In theory, you could measure how much heat would creep up in set amount of time so you can know exactly how much you need to purge at what interval. Question is only how to actually do it as this is something a firmware would have to support as you have no idea in G-Code what amount of time passed. Some half-way solution, of course, would be to do it from g-code and purge "more than required" and "more often than required" but should work IMHO.

Snip!

Or maybe I try and make my own custom heat breaks with PTFE liners and only print low-temperature filaments.

This is where I stopped my work. Basically, in all-metal hotends you need to have some clearance around the filament to allow for thermal expansion. PTFE is soft and slippery enough that you can have a tight seal. If you don't have that seal, molten material gets pushed up into the thermal break far enough it causes issues.
Add the fact that my design requirement was to be able to print TPU and PETG in the same part. The TPU compresses and gets pushed back into the thermal break. Not good. Gave up.
I did think about things like silicone seals at the base of the thermal break. But frankly I think mixing heads are just a bad solution and need far too much complexity to be worth it. So long as you can index the nozzles accurately between 2 or more extruders, there's no real advantage to mixing heads (unless you really are going to mix).
At the end of the day you have a printhead that requires two (or more) filaments to even function at all. I don't think mixing heads have a large enough market to be worth the trouble.

Although now I'm nostalgic for a 'mixing' head I saw several years ago at the NY maker faire... he wanted to run about 12 filaments, and liquids and god knows what else. I'm fairly certain that never worked.

You still get the "cooking" issue. I don't have enough experience with PLA (I don't think PLA reached even 1% of the filament I printed), maybe it does not suffer from that too much but it's still a problem.

As for low temp vs high temp, looking through history, all the fancy all metal hotends have some kind of issue with low temp filaments, OTOH the hotends that play nice with those low temp materials will be terrible at the high temp ones. IMHO the only real solution is to have a "head per material" setup.

What do you consider a 'low temp' or 'high temp' material? There has been at least 1 extruder on the market that (if fitted with a better sensor) could print in ULTEM or PEEK, was also very good with PLA, maybe the best with TPU. It couldn't print wax to save its life...

This is something I do since day one.. on my rapman I had 4 complete extruder assemblies one for PP and HDPE, one for ABS with .5mm nozzle and one for ABS with .25mm nozzle.. for e.g. for my I3 style printer I made a modular X carriage so I can easily swap the head (single screw)
https://www.thingiverse.com/thing:2039960
and there I have a PTFE lined hotend (some old design of mine) for PLA, again my design for 3mm filament with 1mm nozzle for PP/HDPE, some all metal 3mm with bmg, all metal 1.75mm with remote direct drive, dual hexagon full metal with dual remote direct drive etc etc..

I have sitting in pieces the e3d's toolchanger (no time to assemble) that I hope will be the final solution... we'll see,

I'm not convinced that the e3d design is the way to go (a magnet is all that stops the head from falling off? Really? So no high-speed printing then.) but its an early attempt and sold as an experiment.
But the concept, tool changers, is absolutely the way to go. We are lucky that RRF and duet 3 makes that a practical option now.
If you really want to go crazy, you can even add a Palette to such a machine. 4 colour head for PLA, plus more heads for other stuff.

in the meantime I'm looking to buy some el-cheapo UV printer so I can design and print a proper connector with pogo pins or something similar that I would like to use for the extruder assembly...

Why print something that already exists?

https://www.mill-max.com/

(Yes, I get the irony of saying that here, of all places)

deckingman

@arhi said in What do you think about Dragon Hotend:

..................Slowly going trough Danal's work .............................

You did it again...

I have an RPI - it's bolted to the printer but that's as far as I've got with it.

To clean carbonised or blocked nozzles and stainless steel heat breaks, I wouldn't for one minute suggest that you should try putting them in an oven which has a pyrolytic cleaning cycle. Because that cycle typically reaches about 500 to 600 deg C which will burn away any plastic and leave nothing more than some loose ash which is easily removed with soft brush. It won't damage stainless steel, brass, or copper but it's too close to the melting point of aluminium so don't try it with a complete hot end. Of course you should never try this in any case because burning off plastic could release toxic fumes. That's why I wouldn't ever suggest you try it. But hypothetically speaking, if you take precautions about ventilation and so forth, it does work.

fcwilt

@theruttmeister said in What do you think about Dragon Hotend:

Will suck with PLA. Heatsink is waaaaay too small.

The heat sink is similar in size to the Mosquito and the M works fine.

Why do you think the Dragon would be different?

Thanks.

Frederick

arhi

@theruttmeister said in What do you think about Dragon Hotend:

Yes. There's an awful lot of people who are still building things like that dragon hotend, and have clearly never seen the early dev work done by NopHead.

Yup, all the work NopHead and Arcol did shows many of this things are going in the wrong direction. Most of Nop's stuff is still available, Arcol killed his blog and the few forums he was active as are dead and non existing now. For some reason he was never accepted on reprap.org as his idea was always to make the commercial and not open design and the community really disliked that. Nop's work was also not that popular due to him keeping lot of details about his machine for himself (he was running combo of python on stronger computer with stepper on mcu 10+ years ago) as noone could reproduce his awesome results and while his posts were always super informative and full of real engineering and real math ppl kinda like YT flashy stuff and not something with substance

It actually looks like the hotend Prusa was waving around about 7 or 8 years ago that he never got to work.

I remember that one and was actually trying to find the video and pics but could not. It was before Prusa Research while he was still just a Czech student. If you find some links share

there's no real advantage to mixing heads (unless you really are going to mix).

That's the think @deckingman is trying to do, he's trying to make a new hotend that will actually mix the filament as diamond is not mixing them (you can read his text about "toothpaste effect")

What do you consider a 'low temp' or 'high temp' material? There has been at least 1 extruder on the market that (if fitted with a better sensor) could print in ULTEM or PEEK, was also very good with PLA, maybe the best with TPU. It couldn't print wax to save its life...

which one?

ATTM I tested mosquito and it prints both PEEK and PLA

E3DV6 I used to print wax filament made by Kai. Never tried anything hotter than nylon on E3DV6.

I'm not convinced that the e3d design is the way to go (a magnet is all that stops the head from falling off? Really? So no high-speed printing then.) but its an early attempt and sold as an experiment.

I did not make my toolchanger design in 10+ years I'm in 3D printing and I was thinking about it since day one. No clue if it was lack of time, knowledge, ideas... but I never did it. That's why I purchased this one to use for a while and learn from all the bad decisions they made (and acknowledge good ones), before I decide how to proceed.

Why print something that already exists?

I looked trough I think 500 different connectors and was not satisfied with what I found. I'll go trough this site too. I prefer to purchase a working solution than to invent hot water but so far nothing I found was fitting my vision

arhi

@deckingman said in What do you think about Dragon Hotend:

You did it again...

I have an RPI - it's bolted to the printer but that's as far as I've got with it.

I mostly use orangepi's as they were more powerful and cheaper/easier to get here but I have bunch of rpi's too. We (oracle-mysql) started supporting arm cpu recently so I have whole bunch of them for testing .. I have them in raid, solo.. some I use with 3d printers with octoprint... I took one rpi4 on the side to try this RRF integration .. that's where I run duetlapse

To clean carbonised or blocked nozzles and stainless steel heat breaks, I wouldn't for one minute suggest that you should try putting them in an oven which has a pyrolytic cleaning cycle. Because that cycle typically reaches about 500 to 600 deg C which will burn away any plastic and leave nothing more than some loose ash which is easily removed with soft brush. It won't damage stainless steel, brass, or copper but it's too close to the melting point of aluminium so don't try it with a complete hot end. Of course you should never try this in any case because burning off plastic could release toxic fumes. That's why I wouldn't ever suggest you try it. But hypothetically speaking, if you take precautions about ventilation and so forth, it does work.

Interesting. I assumed that once carbonized exposing it to even more heat would not help but only worsen the situation so I always used mechanical way of cleaning. Normally I'd leave it in acetone for few days, then move the acetone container with nozzle to the ultrasonic cleaner than remove from acetone and put directly in to ultrasonic bath with some cleaning detergent heated to 70C and after that - mechanical cleaning.

theruttmeister

@fcwilt said in What do you think about Dragon Hotend:

@theruttmeister said in What do you think about Dragon Hotend:

Will suck with PLA. Heatsink is waaaaay too small.

The heat sink is similar in size to the Mosquito and the M works fine.

Why do you think the Dragon would be different?

Thanks.

Frederick

I dunno, I've not done testing on either of them. But given the mass and surface area of the heatsink, plus the lack of any information on how the stainless tube is attached to the copper (if its not a press fit, that's a problem). I would expect it to be sub-optimal.
But then I disagree with the design choices made on the mosquito as well.

Simply saying a hotend 'works' isn't much of a measure. If I actually got off my behind and made the testing rig I designed ages ago I would measure force required for a given extrusion rate, which is the type of metric that would allow us to actually measure if a given hotend design is better or worse than any other. But I haven't, so I shouldn't complain too much.
But my hypothesis is that both of those hotends would require less force to extrude if they were fitted with larger heatsinks.

jens55

@deckingman said in What do you think about Dragon Hotend:

@arhi said in What do you think about Dragon Hotend:

To clean carbonised or blocked nozzles and stainless steel heat breaks, I wouldn't for one minute suggest that you should try putting them in an oven which has a pyrolytic cleaning cycle. Because that cycle typically reaches about 500 to 600 deg C which will burn away any plastic and leave nothing more than some loose ash which is easily removed with soft brush. It won't damage stainless steel, brass, or copper but it's too close to the melting point of aluminium so don't try it with a complete hot end. Of course you should never try this in any case because burning off plastic could release toxic fumes. That's why I wouldn't ever suggest you try it. But hypothetically speaking, if you take precautions about ventilation and so forth, it does work.

Rather than heating up a big oven, a plumbers propane torch does wonders for cleaning nozzles... and it's very quick!
More importantly, it doesn't get SWMBO wound up.

theruttmeister

@arhi said in What do you think about Dragon Hotend:

That's the think @deckingman is trying to do, he's trying to make a new hotend that will actually mix the filament as diamond is not mixing them (you can read his text about "toothpaste effect")

Static mixing or active? Because sealing an active mixer is a challenge.

What do you consider a 'low temp' or 'high temp' material? There has been at least 1 extruder on the market that (if fitted with a better sensor) could print in ULTEM or PEEK, was also very good with PLA, maybe the best with TPU. It couldn't print wax to save its life...

which one?

Type A Machines G2. Not that you can do anything useful with ULTEM or PEEK without an oven to print inside... Plus you can't buy that extruder any more.

Why print something that already exists?

I looked trough I think 500 different connectors and was not satisfied with what I found. I'll go trough this site too. I prefer to purchase a working solution than to invent hot water but so far nothing I found was fitting my vision

I know the feeling. But just used some of the mill-max SLC components on a project. If I try and build a tool changer with electrical connections, I'll use something from them.

arhi

@theruttmeister said in What do you think about Dragon Hotend:

Static mixing or active? Because sealing an active mixer is a challenge.

static mixing using "weird paths" like those multi-component mixer attachments on the industry syringes ..

https://somei3deas.wordpress.com/2020/02/24/my-6-input-51-mixing-hot-end-version-2/

there are 9 parts of that, I find it super interesting

I know the feeling. But just used some of the mill-max SLC components on a project. If I try and build a tool changer with electrical connections, I'll use something from them.

I just went trough the site, they have the pogo pin modules I was planing to use but they don't have a "connectors" with guides, locks etc etc.. I did not plan to use just blank pins and house them in my case (if I don't have to :D) but to pack bunch of stuff like this into a mating pair:

theruttmeister

@arhi

I think the closest are these
https://www.mill-max.com/products/new/rugged-spring-loaded-wire-termination-connectors

But no, not an actual connector. But if you are building a tool changer you don't need a connector, you need to design the electrical connections into the tool mount.
A simple PCB, that carries SLC's and breaks them out into maybe Molex KK connectors, and locates accurately on a machined aluminium mount that holds the printhead. With a matching PCB and mount on the printer...

That's how I ~~did~~ would do it.

You could also just use the ones I linked to and bolt them in position.

Although if you are only going to use 2 tools, and don't need to be able to swap out the heads super fast, just regular connectors would work.

fcwilt

@theruttmeister said in What do you think about Dragon Hotend:

I dunno, I've not done testing on either of them.

Perhaps you should. I tried one M and was so impressed that I equipped my other printer with one.

I like everything about the M. If it has a downside I have not found it yet.

Time will tell.

Frederick

zapta

@jens55 said in What do you think about Dragon Hotend:

Rather than heating up a big oven, a plumbers propane torch does wonders for cleaning nozzles...

That's what I do, with a small cooking torch, but arhi's comment here about toxic fumes made me rethink it.

deckingman

@jens55 said in What do you think about Dragon Hotend:

Rather than heating up a big oven, a plumbers propane torch does wonders for cleaning nozzles... and it's very quick!
More importantly, it doesn't get SWMBO wound up.

In my house, 'er in doors doesn't object to getting her oven cleaned. Speaking hypothetically of course, but if one were to put a heat break in the oven, one doesn't necessarily have to tell anyone If you go about it the right way, you can even earn brownie points. Be careful with that torch - it's not too difficult to anneal stainless steel if you get it too hot.

arhi

I managed to kill aluminium nozzle with a small proxxon torch so I don't go with torch near my nozzles any more.

Don't put "non food" in the oven, dunno, small kids, wife, life's short either way without needed to explain what/where/why... Will be moving, hopefully this year, to a house where I'll have a proper work space (I will have a small 50m2 house just for me ) and there I plan for plastic-dedicated oven for my recycled plates (I recycle failed prints, support, iterations.. into plastic plates I later on machine and use for other builds) and for other stuff but now when space is scarce I have to restrain myself and worry about WAR (wife approval rate)

theruttmeister

@fcwilt said in What do you think about Dragon Hotend:

Perhaps you should. I tried one M and was so impressed that I equipped my other printer with one.

Perhaps I should. The load cell is just gathering dust and I've not done a blog post in about 6 years...

Might be interesting to do 1 hotend a month, proper quantitative benchmark.

theruttmeister

@arhi said in What do you think about Dragon Hotend:

@theruttmeister said in What do you think about Dragon Hotend:

Static mixing or active? Because sealing an active mixer is a challenge.

static mixing using "weird paths" like those multi-component mixer attachments on the industry syringes ..

https://somei3deas.wordpress.com/2020/02/24/my-6-input-51-mixing-hot-end-version-2/

there are 9 parts of that, I find it super interesting

Interesting.
The huge volume of the melt chamber is going to be an issue... he'll have epic purge requirements. And its funny that he thinks there is IP in static mixing device design (hint, if hundreds of pounds is a lot, you can't afford patent enforcement), static mixers have been around forever and are well understood.

I just look at the endless number of sealing surfaces... I get the desire for CMYK mixing. I just think that 99.9% of people are happy with a low maintenance hotend and a wide range of available single colours. Just using the 4 colours of a Palette is a big jump in complexity for design.

Good luck to him.

fcwilt

@theruttmeister said in What do you think about Dragon Hotend:

Might be interesting to do 1 hotend a month, proper quantitative benchmark.

Now that would be great!

Frederick

deckingman

@theruttmeister As I'm being talked about, I thought it best to respond. I've been using "mixing" hot ends for many years. But none of the commercially available options actually mix. So I am stuck with the stripey toothpastes effect. If I could buy one that actually mixed I would as that would save me a lot of time and money.
It's fair to say that 99.9 % of people are happy with a low maintenance single input hot end. It's also fair to say that very few people would buy a mixing hot end, not least because each input needs its own extruder.
But I'm coming from the basis that I already have six Bondtech BMGs. These are mounted on a second CoreXY gantry which sits above the hot end. This was the first CoreXYUV for which the Duet guys wrote a new kinematics. I also have a third load balancing gantry so now the machine is a CoreXYUVAB. This was another world first.
I'm proud of the fact that both my CoreXYUV and my load balancing gantry have been implemented by others because I feel that I have made a contribution towards advancing FDM printing.
I also "invented" a technique for advancing the tool change point within the gcode file which negates much of the required purge. Again, I have openly shared all this information and the Duet guys have previously stated that they might implement this in firmware.
If I can make a hot end that actually mixes, then that will be something else that will move FDM printing forward. I don't really care if the 99.9 % of people won't be interested. If 0.1 % of people do benefit, then that will be an achievement.
Thus far, I haven't made a bean from all the work I have done over the years, so it would be nice if I can find a way to get some return on this mixing hot end if I ever get it to work. But that is secondary. The main thing for me is solving the problem.

jens55

A wild thought here .... commercially used two part epoxy actually 'mix' the two separate epoxy parts in a nozzle. It is a very effective mixing action. Have you ever tried implementing something like that to get rid of the toothpaste effect?
The only issue is that the mixing chamber, by the very definition, needs to be larger in volume than a straight through path and so there will be a delay to the mixing effect. A purge tower will be needed (don't remember if you are currently using a purge tower).
Manufacturing the mixing chamber would likely be quite tricky.