Can You 3D-Print a Stator for a Brushless DC Motor?

Betteridge’s Law holds that any headline that ends in a question mark can be answered with a “No.” We’re not sure that [Mr. Betteridge] was exactly correct, though, since 3D-printed stators can work successfully for BLDC motors, for certain values of success.

It’s not that [GreatScott!] isn’t aware that 3D-printed motors are a thing; after all, the video below mentions the giant Halbach array motor we featured some time ago. But part of advancing the state of the art is to replicate someone else’s results, so that’s essentially what [Scott!] attempted to do here. It also builds on his recent experiments with rewinding commercial BLDCs to turn them into generators. His first step is to recreate the stator of his motor as a printable part. It’s easy enough to recreate the stator’s shape, and even to print it using Proto-pasta iron-infused PLA filament. But that doesn’t come close to replicating the magnetic properties of a proper stator laminated from stamped iron pieces. Motors using the printed stators worked, but they were very low torque, refusing to turn with even minimal loading. There were thermal issues, too, which might have been mitigated by a fan.

So not a stunning success, but still an interesting experiment. And seeing the layers in the printed stators gives us an idea: perhaps a dual-extruder printer could alternate between plain PLA and the magnetic stuff, in an attempt to replicate the laminations of a standard stator. This might help limit eddy currents and manage heating a bit better.

33 thoughts on “Can You 3D-Print a Stator for a Brushless DC Motor?

  1. Here’s a headline that can’t be answered with a “No”:

    Does Hackaday reuse the opening line “Betteridge’s Law holds that any headline that ends in a question mark can be answered with a “No.” twice in one day?

    Yes, yes they do.

    1. Except there is an editorial rule that says “Don’t ask rhetorical questions about established facts in a headline” So the headline would be “Hackaday opens with Betteridge’s law twice in one day”

  2. “And seeing the layers in the printed stators gives us an idea: perhaps a dual-extruder printer could alternate between plain PLA and the magnetic stuff, in an attempt to replicate the laminations of a standard stator. This might help limit eddy currents and manage heating a bit better.”

    He had trouble with the PLA one deforming due to heat. So I’m not too sure if doing a dual material would help much. Considering the magnetic filament is most likely ferrite powder based and would give minimal heat dissipative ability. As for eddy currents again it was the PLA one that started to melt. Meaning the coils of the motor were getting hot enough to start deforming the PLA. I don’t think an eddy currents were at play. Even in the video he shows 12v at .5 amps before the camera cuts to a different shot, 6 watts is pretty warm especially with nowhere to dissipate to. Even if a good portion of that watts is in the switching fets.

    1. I was wondering about the feasibility of a dual extruded print too. The heat is a bigger problem but one that might benefit from a different plastic that has a higher temp melting point.

      I also wonder how other factors like layer height and filament feed rates might affect things and if there are any post processing steps that could improve the performance of the stators.

    2. It melted because he didn’t have the ESC setup correctly to spin it. Rather than figure out what was wring he kept increasing the current until it melted. With it spinning there should be some airflow to help control the stator temp.

  3. Wondering if custom making and extruding the filament… then printing will result in more feasible success. Then again… might require a different type of printer to print, sinter and heat/magnetic treat the printed product.

    1. It won’t. You’re limited pretty severely in how much iron can be added to the plastic and still have it flow well enough to print, and the actual amount of iron in the filament is pretty low. I suspect you’d likely get worse results trying to mix it yourself- I expect the manufacturer did a lot of experimenting and tweaking with the mix and there’s probably not much room for improvement.

      Sintered metal printing would probably work a lot better, but that isn’t remotely practical for home users (at least not currently, maybe one day I hope).

      1. You can probably even come up with a mixture that you can sinter in a kiln. Leaving you with more or less “pure” metal.
        That said lots of steel sheet, a half decent cnc router and Epoxy is probably the best bet. It would take hours and hours, but that never stops anyone…

  4. Why, oh why, oh why must people repeatedly waste vast amounts of time and effort on rhetorical questions? I am losing much respect for those whom I once respected greatly. Maybe, just maybe, if people spent their time and energy on legitimate questions, we could get some legitimate answers.

    1. “Why, oh why, oh why must people repeatedly waste vast amounts of time and effort on rhetorical questions?”

      I hope your rambling answer to your own rhetorical question about people wasting time on rhetorical questions was intentionally ironic!

    2. Sometimes, that’s how you get a new answer. There have been many inventions that only came about because someone revisited a question that everyone “already knew” the answer to in a new way and came out of it with something of use.

    3. @TheWizard: Good one!

      My other favorite is whenever anyone says “pedantic” or “patronizing”, I correct their pronunciation of the word — wrongly or rightly, the joke still works.

      “Actually, that’s pronounced pah-tronizing.” “Technically, that’s pronounced pay-tronizing.” Antics ensue!

  5. Fan to dissipate the heat? Brilliant idea: put another fan blade on the shaft of the DC motor, and have the breeze from the fan help turn it.

    Geeez, stop it! I can hear all the hissing and booing already, without even having posted my suggestion.

  6. The iron powder isolated in the PLA takes care of the Eddy current problem for the most part. This is probably just ohmic heating. Some motor and transformer parts are made with sintered powder for just that reason. At a minimum he needs a much higher ratio if iron to PLA????

  7. I think a large part of your heating problem (besides having a stator with a low melting point) is that plastic is a poor conductor of heat. Adding more metal to the stator will create more hot spots insulated with plastic, and that plastic will melt. Can you print without metal, or maybe even a ceramic?

  8. How bout we stop calling them BLDC motors. The motors are hardly DC. They are fed a 3 phase AC current by a controller. Its like calling a diesel locomotive train an electric train. Sure the traction motors are electric, but it still belches out diesel exhaust from the onboard generator.

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