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3D printed plastic burner experiments (photo heavy)

Another FrankenBurner

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I have been tinkering with burners for a number of years now, but the hard part was making the burners to test the ideas.  In burners 101, John in Oly, WA had posted about some of his experiments in the vortex burner range.  His experiments were created in part with a 3D printer.  Seeing what he had done, I had a mind blown epiphany about 3D printers and prototyping.   I knew almost nothing about them at the time.  I learned about 3D printers and purchased one.  I then had to learn about their idiosyncrasies, as well as 3D modeling and slicing the CAD models.  As my CAD skills improved, my experiments got more complex.  I usually print a burner head which fits a mix tube with nozzle.  It is great.  Have an idea, produce it reliably.  Need to change it a just a little bit, reproduce it with those minor changes.  Rapid prototyping.  Click print and go to bed.  

I am playing with half inch mix tubes currently as they are big enough to be less picky but small enough that the prints are smaller.  These are just so I can learn currently.  I intend on casting some of the better models in aluminum.  I also intend on eventually scaling to 3/8 and 3/4 burners once I am content with a few designs.   

I have a range of mix tubes precut from 7 inch to 2 inch at half inch increments, I have a few accelerator assemblies built and I have a few exit nozzles of different types.  This allows me to quickly play with mix tube length, jet diameter, and nozzles without much fuss.   

Here are my experiments so far (in CAD form):


I am whimsical with the version numbers.  Some major failures in between. 

I have been labeling the burner heads in 3 sections.  The accelerator block at the top, the ribs in between and the outlet below the ribs in the images.  The nomenclature could use some help.  The entrance to the "outlet" is an inlet.  I haven't put much thought into it.  The terms evolve as I gow.  For a while the ribs were labeled vanes.

Version 1: Learning CAD mostly.  A small trumpet shape at the entrance of the outlet and crudely shaped ribs.  I was working with the Mikey burner as the initial start concept.  Not quite a tube burner as it decreases in size.  I did not account for wall thickness on the 1/2 pipe in the trumpet so there was an abrupt corner unless the pipe was chamfered.  Even with this, it produced a nice strong flame at higher pressures.  It is the first flame I posted in burners 101.

Version 2.5: A large improvement.  The ribs are a bit smoother.  I was going for a cutting edge and encouraging vortex (thanks to Mikey).  A longer trumpet shape which exits in a smaller diameter to match the ID of 1/2 pipe.  I posted some images of it's flames.  

Version 2.6: I reversed the direction of the ribs to encourage vortex the other way.  Apparently I thought I was inducing a hurricane in the Northern hemisphere and so the coriolis effect needed tending to.  I must have thought highly of myself at the time.  I later wised up as the proof is in the pudding.  Have to learn some how.  I did radius the "cutting edge" but did not notice any major difference.  I also decreased the length of the ribs so the air inlets surface area was in the neighborhood of 200% of the area of the throat.

Version 2.7.1: I studied airfoil design and realized I had things all aerodynamically backwards.  I reworked the rib shape and I also added a second axis of rotation to the ribs playing with vortex some more.  It performs very well but I've barely had a chance to tinker with it.  It got dubbed the twirly burner somewhere along the way.

Version 3.2: This burner came before version 2.6 and 2.7.1 as I was playing with lower velocities (thanks to Frosty).  It is a linear design using the wasp waste geometries.  I initially posted an image but didn't have much time to play with it.  At that time it was running higher velocities with a smaller mig tip.  I eventually bored out a mig tip to 0.032 actual in an attempt at lower velocities as I was inducing too much air at higher velocities.  I posted an image of that flame as well.  Then a few posts later, I explained the burner in a bit more detail.  It needs a bit of work but I wanted to dabble into lower velocities.  

Version 3.3: Why not?  Take the ribs from 2.7.1 and plop them onto 3.2.  Not so much to test an idea, this one it just for fun.  I just CAD and printed today so I have no clues about him.  I suspect higher velocities will be required as there is more drag from the ribs.

They all use a sliding choke as it seems to do the best job of variable regulation and not just an on/off kind of thing.

OK. OK.  Real pictures.  I only have a few.  I was focused on the flames, not the burners mostly.  

Here is ver2.5 in a fashionable pink:  (My daughter realized the printer can make toys)


Here it is in the vise, setup for it's flame photoshoot:


Here is 2.7.1 up close after some sanding:


My final image is 3.3 warm off the printer still:


I will add more images as I continue on.

I can print in finer detail but for prototyping, it prints faster this way and it doesn't seem to influence it much.  When I go to aluminum, they will be printed finer.

As always with me, any discussion, suggestions, criticisms, or ideas are welcome and wanted.

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Cool stuff. Consider me an interested onlooker.  I don't know enough about this stuff to have any real suggestions or criticisms, but I wanted to let you know that I'm very interested in your results, so please keep us posted on your progress.

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Curtis: Very cool, I'll be an avid watcher you know. Rather than printing al have you considered printing patterns and having them cast? 

Theo Naz has been printing patterns to cast guards, pomels, etc. for some time now. I'm thinking you could do all but the exhaust nozzle in bronze. The final "nozzle" flare could be SS the bronze will dissipate the heat to the fuel air flow quickly enough to protect the burner. Hmmmm?

Frosty The Lucky.

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I have been looking for a way to invite the interest of home casters; they have a lot to teach blacksmiths about some of these subjects; not to mention that 3D modeling is the perfect tool for helping to manufacture up to date equipment. I hope John in Olympia will jump into this discussion with both feet :D 


It looks like you have settled the question of whether or not spiraling air opening are worthwhile; they are :)

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I'm really excited about this one! Curtis, you've probably already come across it but I thought I would mention it in case you haven't yet: you can do "Lost PLA" and burn it out but an even better option is wax 3D printing filament. MachinableWax makes one and there are several other brands as well. It is a bit tricky to print with from what I've seen, but the burnout is supposed to be a lot cleaner and easier (it is designed specifically for this purpose). 

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Buzzkill:  I intend to post anything note worthy going forward.  I held back in burners 101 so as not to hijack it with my feats and failures.  

Gibson:  I am using a Creality Ender 3 printer and a 0.2mm layer height for the quick prints.  I go to 0.1 and 0.05 for finer prints.  

HojPoj:  PLA filament currently. 

Frosty:  I had not thought of bronze cast but I have been printing in plastic and lost PLA casting them in aluminum.  Symmetric models can be split and go to green sand.  I had the same thought, the FAM stream cools the entire assembly during running and the choke is closed at shut down.  If need be, heat radiating fins could be added to the mix tube if the FAM didn't provide adequate cooling.  So far, in plastic, the only time heat was a concern is when I bring the nozzle into the orange ranges with a shorter section of mix tube.  Even then, no plastic heads have melted down because of it.  Only one Chernobyl incident which was due to a partially open needle valve and a partially open choke at shutdown.  So far I have been using the steel mix tube as a safety net between the nozzle and the plastic because all testing has been open air.  If the entire mix tube were aluminum, I'm not sure yet.  Though, my thoughts were to design the forge to keep the flame off of the burner completely by casting the final nozzle into the forge with kast o lite or metrikote.  Just have to balance the velocities.

I had another thought you might like.  3D printed forms for NARB blocks.  Custom count, dimension, and taper for the ports.  I will get there when I am satisfied with the burner play.  I suspect more smaller ports means a shorter block to maintain laminar which might be adequately cooled with lower input pressures.  Also, the ports could be sized according to their position for even FAM distribution across the plenum.  

Mikey:  Part of my 3D printer epiphany was the ease of manufacture.  Once I have some of the bugs worked out, anyone with a 3D printer, or who has a friend who has one, or who can order from the online 3D printing services (some of which can deal in stainless steel "prints") can have one with exacting specifications.  As to the spiraled air openings, I have not determined their practicality yet.  I need to reproduce some of the burners with the exact same airfoil shape minus the spiral and see if difference is noticed.  I'm not sure if they help or just get in the way.  They sure look cool though.

Gibson:  I have come across lost casting.  I have also discovered MachinableWax but I will have to change up printers as it is too soft for my extruder type.  There are plans in the works for a home brew printer with dual extruder for printing in wax with one and a water soluble filament for support structures in the other.  For now, lost PLA works and clean burnouts are easily obtainable with controlled heat cycles.  In my case 2 hours at 100C, 2 hours at 200C, and 4 hours at > 500C.  It is mostly a drying, then a melt out, then a burnout of any trapped portions.  The molds come out completely white with no remnants or charring.

Here is a shot of the home brew heat treat oven built for this purpose with some burner heads ready for burnout:



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Frosty, I had another thought.  It would probably disrupt the FAM stream but if the entire mix tube were aluminum, fins of some kind could be printed inside the outlet end of the mix tube.  This would act as a heat exchanger to both cool the mix tube and preheat the FAM.  It would have to be balanced to prevent suck back and also melt down.  High output burner melt down sounds like no fun.  I have 2 shutdown ball valves(one at each end), the idle valve assembly, and the final needle valve.  I like safety nets.

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54 minutes ago, AnotherCurtis said:

Frosty, I had another thought. 

Could you add ridges instead of fins? Similar to what they do with competition rifle barrels. Just a slight increase in surface area has a dramatic effect on heat transfer and might cause less disruption than fins

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VainEnd84: I can add anything we all can come up with if it is described concisely.  What do you mean by ridges?  It might just take me a bit to learn whatever I need to in order to model it.  I had toyed with the idea of dimples down the mix tube, like the surface of a golf ball.  I like ideas.

Enewguy: I have a model(2.8) similar to 2.7.1 but the ribs continue the entire length of the trumpet into the mix tube.  I haven't printed it yet but I suspect that the ribs will actually act as a stop in the vortical flow within the trumpet shape.  I will be playing with the devices in water to gain a better understanding of the dynamics (thanks frosty).  At that point I might know whether is would be better to try to control the vortex like that or just encourage it and let it go organic.


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So they used to  make a fire hose nozzle "cellar nozzle" that spins. I found a video called cellar nozzle at work on YouTube 

Is your burner NA? If not you could make a 2 piece tube with a piece inside that spins to create the vortex. Of course you would have to play with the inner nozzles angle a bit.

If it's NA, I wonder if straw like tubes going around and around within would allow it to start spinning enough to vortex as it excited the main tube

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Awesome setup Curtis! 

When you start looking to build your new printer give the Prusa i3 Bear variant (by pekcitron)  a look. It is intended as an upgrade path for the Prusa i3 MK2/MK3 printers but can also be self sourced. It offers a lot of rigidity and is a great platform if you're wanting to push speeds without a loss of precision. Also sourcing it yourself you get the option to chose which multi material workflows you like the best. It is a really well documented platform with a lot of compatibility with the standard Prusa upgrades out there.

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I wouldn't know how to calculate a progressive rate for internal fins or ridges in a mixing tube. Maybe make a little anemometer that could be run up and down the tube but wouldn't disrupt the flow? Interesting thought but I don't know.

Think rifling in a rifle barrel for a visual. Smooth perhaps air foil shaped. Yes?

I'd just make the burner thin and make sure the nozzle was a low heat conducting material. SS to start but perhaps make a core so it was easy to cast the nozzle into the forge liner.

Another thought I'd kicked around a while back was to dimple the inside of the whole burner like a golf ball. The idea was minimize friction to increase flow and induction while making hundreds of low pressure zones to perhaps enhance propane air mixing. 

Makes me wish I had access to 3D printing but I have trouble even doing simple CAD since the accident. Just too many useless bells and whistles, menu after menu to do simple tasks. I just can't handle it anymore.

Frosty The Lucky.

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Are you considering posting your designs to Thingiverse?  Printing the parts for casting had been on my list for awhile,  particularly for a NARB, just haven't gotten to experiment with the holes and sizes. 

For the interface to the mixing tube,  are the intakes  using threading,  or just slipping over the pipe section?

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Enewguy:  These burners are all NA.  Introducing things of that sort add resistance and possibly get in the way.  Mostly, they are above my current intellectual pay grade.  My current direction is to streamline everything which is why I am striving for lower velocities.  Lower velocities make it harder to induce enough air, mix it properly, and output it at the right velocities.  Once I have done some figuring out there, I will play with increasing the velocity and adding purposeful turbulence to do my bidding.  I really suspect the end result of all this will be middle velocity induction device feeding an equally experimented NARB.  The extra velocity to afford us the extra turbulence while also outputting higher btu's with a smaller induction device.  If the proper amount of air is induced and mixed, the only velocity that matters is the flame exit velocity and nozzles let us play with that, as long as we account for them.  It's all about balance.  At least this is all as I understand things currently.  Ask again tomorrow.  

Gibson:  Thank you for the information.  I will look into it.  My father and I have built a number of CNC machines (router table, mill, plasma table) and figured we would give a printer a shot, seeing how simplistically the Ender 3 and CR-10S are built and still function very well.

Frosty:  I had the same golf ball dimple curiousity.  As to the accident, that sucks.  I too have dealt with a major health crisis recently which affected the processor.  For a time, I was very concerned that I would lose that part of myself and it bothered me as much as the concerns of possibly dying soon.  What you have been dealt, I feared very much.  I have to work within the new rules of my damaged mind but it sounds like you have a much longer list of new rules.

VainEnd84:  I got it now.  I thought fluting was about bringing the weight down.  

HojPoj: I doubt I will upload the files to Thingiverse.  I worry of liability when talking of high output burners and uploading them onto a site which isn't about them for just anyone to find, irritates that worry.  I am considering uploading them here eventually once I have more time to narrow down what I am doing.  Frosty once brought up some images of an old bad design he wished would go away and I am trying avoid that.

The mix tube is friction fit.  I imagined a little better centering that way, even though the pipe could be eccentric a bit.  Also, the NPT threads are a fun one to CAD so slip fit is easier to prototype.

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I made it out to the shop to get some proper images.  I didn't have much time to tinker with the new versions so I still don't know much about them.  As suspected, version 3.3 demands higher velocities then version 3.2 but hasn't been evaluated for mix tube length, accelerator diameter, or flame characteristics.

Here is a lineup of the toys and some background clutter:


Here is a shot to show 2.7.1 hosting fire.  The flame looks terrible but that is due to exposure mostly.


When getting images of flames, it is very difficult to get them to look like they actually do.  To demonstrate, here are some examples.  All images are the same burner, as above, at the same pressure, taken at the same time.  The only change is the exposure settings.  What was actually witnessed was the nozzle color from the left image and the flame from the right image.  As you can see, the left image makes the flame look very rich and the secondary flame looks huge and some what lazy.  The middle image looks still rich with a smaller less lazy secondary flame.  The right image, the flame looks pretty good with a ghostly straight secondary flame but the nozzle looks relatively cold.  


I played with 3.2 some more and was experimenting with low end output.  This is coming directly out of 1/2" pipe1733346908_smallflame.jpg.5691a0782178d1307b0258e0616607a8.jpg:

My father has been working on the molds and we had a failure.  The molds come out perfectly clean but it cracked during cool down so we will be adjusting the cooling program:



If anyone who knows more then me (big crowd), ever sees anything I got all wrong, please educate me.  I like to do things the smarter way and I don't have a problem with correcting my wrongs.  

For now, unless there is a lightbulb moment, I am going to tinker with what I have on the table until I am satisfied.  Then I am going to try to select one of the versions or create another version from my learnings so I am working with a single version and making small modifications to it.

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Very cool AFB! Fun to experiment with the burners, but I got hypnotized by the flame vortex coming out of the nozzle. Don't know if it was an effective burner, but it looked great looking straight back down the center of the flame and watching the vortex swirl.

I played with the wax filament on my 3D filament printer. I had to modify the filament feeder so the gear tension could be lightened up. The stock feeder gear spring was too much for the soft wax filament - would crush the filament and cause jamming. The other thing I had to modify was the firmware. It had a low temp limiter for the nozzle heater. The wax filament needs a nozzle temp of about 142C, IIRC, and the printer would only allow it to be set at a minimum of 175C. After those mods, it worked fine printing with the MachinableWax filament.

On your molds cracking during cool down after burnout. How cool are you letting them get? As I've learned the lost wax(resin/plastic) process, which is just scratching the surface, you bring the mold down to about 900-1100F after the burnout, let it soak at that temp until uniform throughout the mold and then pour the metal with the mold at that temp (along with having a vacuum platform to pull the molten metal into the mold).

It would be fun to print the blades of your vortex generator as separate pieces with pins down the center, so you could rotate them from lying on the diameter (don't know the proper terminology) to oriented radially(?) and everything in between.

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Beat me to that question by a long mark, Mike. 

Another question for the other Frankenburner. Have you considered making the intake structure larger in diameter? It wouldn't need to be so long as these proto types but the larger intake flare would induce a stronger vortex with a stronger low pressure zone in the center.

Say maybe increase the diameter of the intake half an inch and see what happens?

Just a thought, my brain won't stop thinking things you know.

Frosty The Lucky.

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1 hour ago, Frosty said:

Another question for the other Frankenburner. Have you considered making the intake structure larger in diameter? It wouldn't need to be so long as these proto types but the larger intake flare would induce a stronger vortex with a stronger low pressure zone in the center.

You got me right back, Frosty. I've been thinking the same thing about larger diameter entrance areas, for exactly the same reason :D

Also, I agree that that their length should be shortened.

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