Compliant Harmonic Drive (3D Printed)

This 3D printed harmonic drive introduces a compliant mechanism to to make a more compact design. I explain what these things are, show my process, develop, and test this actuator.
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[@LeviJanssen]

Whoops! Every time I said "plastic deformation" I meant "elastic deformation". I guess that's what I get for not writing scripts. Also, I filmed this video with a new camera, so I was still figuring out things like focus and white balance. Oh well :)

[@averybrown8136]

I was just coming down to see if anyone had said anything about the deformation😂

[@PiefacePete46]

I guess the important word was "deformation". Didn't notice anything annoying with the camera... focus a little slow on close-ups, but better than most KZbin offerings.

[@wilheldp]

It was elastic deformation of plastic, so I’ll allow it.

[@KeithOlson]

Hmmm... What about making a dual-layer deforming piece, where one layer is conformal to provide springiness and the other incorporates a 'disc-and-socket' joint at either end of a 'bone' for resistance against torque without preventing deformation. Both layers would be part of a single model. There would just need to be a small gap between the disc and the socket to allow for rotation. (Three layers would be better as you can trap the rotating joint in between two conformal hinges, but that would require some thought in regards to support.) Does that make sense?

[@BricksanSticks575]

perhaps if u use metal like what actual springs are made of i could handle more pressure maybe?

[@qupbuqqoywogh1108]

Failure??? You were creative, you designed, you build, you tested, you learned and you shared. Hence, a big success! In one word: IMPRESSIVE!

[@Enkye_ART]

As a close friend once said to me: “We live and we learn. I am now wiser. This is not a complete loss.”

[@fowlerj111]

He was using the term failure in an engineers sense. He was measuring how much torque it took to break the mechanism. If the answer is higher than anything it will see in actual use, then it's strong enough. The safety factor is how much higher. If the answer is too low, he has information about how to adjust the design.

[@glow262]

Failure might just be as useful of a result as a success.

[@jawells1955]

As Thomas Edison said: “I have not failed. I've just found 10,000 ways that won't work.” “Many of life's failures are people who did not realize how close they were to success when they gave up.” I wonder how how two flex plates like you designed installed in opposite direction would hold up.

[@auralynn3862]

Same philosophy here. Despite the mechanism failing (i.e.: reaching a failure state such as slippage or breakage), the process of experimentation was a success as it yielded worthwhile information.

[@sermadreda399]

I think you can give the compliant spring more depth ( not width) it will keep its elasticity and give more support against torque

[@julstr6303]

Maybe also add some radius or chamfer to the attachment point from the spring to the internal and external gear so the plastic won't break at the sharp corner.

[@user-py9cy1sy9u]

@@julstr6303 ^ this

[@maibster]

@@julstr6303 very much dis^

[@frother]

And if you keep adding depth until it's as deep as a regular harmonic drive, you've basically created a stronger (better?) version of the regular harmonic drive.

[@maibster]

@@frother thats not how mafia works

[@BrassLock]

I first saw a 3D printer in Chiang Mai a few years ago and realised how the future would unfold rapidly in the hands of young inventors. You are a great example of how mechanisms can be rapidly prototyped and improved, in ways that could never have been done last century. It's exciting to hear your thought processes, and see your working models.

[@davidaustin6962]

There's a youtube channel where all he does is test people's fan blade design. You should do the same, but with a torque transfer plate (or whatever you call this). I have an idea that I think would work.

[@Barak43]

that's a good idea ^^

[@stephensomersify]

Not sure what i mean - not sketched - 'radial slots'

[@xaytana]

At the very least give the name of the channel, Major Hardware, and you should also better describe the channel as he does far more than just the Fan Showdown series.

[@dapperbrick7516]

@@xaytana I came here to say this. He's a smart guy over at Major Hardware, moreso than he lets on in his videos

[@2danshepherd]

Compliant mechanisms and strain wave drives are both cool. So combining them is even cooler! I'd love to see more development of this project.

[@nikolatotev]

Something that comes to mind, you could alternate the spring "direction" so that for every "left" spring there is a "right" spring. That way the mechanism has support in both directions. Another improvement would be to make the springs thicker vertically.

[@combosloth1677]

you have no idea how much I appreciate you using metric instead of imperial

[@LeviJanssen]

Always have!

[@3DprintedLife]

I honestly don't know any engineers (I'm in the US) that use imperial. The only time we do is when we're forced to by dang archaic machine shops! Metric is love, metric is life

[@ALEXGIBSONCMG]

@@3DprintedLife imperial is less common in engineering, more of a general purpose measurement.

[@henmich]

Come on... how hard is it when the software does all the heavy lifting??

[@JohnMeacham]

Despite being in the united states I have fully metricized my shop, it makes collaborating online so much easier. Highly recommended. Although in my open source designs I try to use 3mm 8mm and 30cm dimensions as much as possible as there are very close imperial standard sizes so people can often use a design as-is with what they have on hand.

[@AleNXT97]

You mentioned that one torque direction could withstand more than the oher. So I thought that you could add the same pattern on the first (in the same part), like it is another 'layer', but mirrored, so it will compensate the inequality. Really loved this design, to me it's the most interesting I have seen that is 3D printed. I think you could expand the research from here to make a very good design, great work!

[@Peter-898]

Another option may be to include springs in alternating directions. That would probably come at the expense of radial space, but would still allow for a low vertical profile

[@LeviJanssen]

I was thinking the same thing, I wasn't sure how to implement it easily. I guess layering it wouldn't be too difficult.

[@gordonpromish9218]

ah, you had the same thought

[@red13emerald]

@@LeviJanssen I mean you could always just print two parts and assemble them together in some way. You could also print supports between the two layers of springs, but those would be hard to remove, I reckon.

[@brianfoster7064]

@@LeviJanssen you can do that as a single print leaving a small gap between the two spring layers keeping a single hub. Also, increase the depth of the springs and gear without modifying the thickness. That should provide more strength without compromising the elasticity. Also, consider using TPE. Though, a TPU spring with PLA center would be even better. That, however, would require a printer able to print with two filaments, or a lot of fun doing it manually.

[@nathanmaher2846]

'Elastically' deformed, not plastically. Also, this project was AWESOME! Please keep developing. Torque is usually expensive - either in size or cost, so cheap torque will always be in demand.

[@LeviJanssen]

Yeah, I had to correct myself at least once, I probably missed other occasions.

[@RinksRides]

...Like Ford Mustangs.

[@bishopp14]

I agree. Keep up the good work! What you're doing is awesome. And interesting to boot!

[@RecreationalOverEngineering]

Very interesting! I like your style of going through the design history, so we understand the reasoning behind it. Keep up the good work!

[@NistenTahiraj]

I think this is now my fav new channel for 3d printing. Original ideas, competitive, first principles thinking, proper testing; keep it up dude.

[@liborferencak8297]

Please continue with this project. Its really interesting.

[@uint16_t]

Amazing work! Well done.

[@Nirossen]

It's cool that people just put information like this out there. There's an entire different side of the spectrum which would try to find ways to patent and close off this knowledge you're willing to share. We really are coming into a new age. It makes me happy.

[@RinksRides]

Brilliant start of something bigger. I'm calling it.

[@ahaveland]

Great work Levi! I have a couple of suggestions - use fillets at each end of the compliant spring to distribute more force and reduce stress risers. You could have more of them per revolution, and you aren't limited to having them in just one plane, so you could layer them up for even greater torque transmission.

[@Magnum3144]

I'm just impressed all around. Well done and nice display of your knowledge.

[@Roadhouseee]

Super cool video dude! First I’ve heard of this particular mechanism

[@MaxMakerChannel]

Very specific, very cool. Loved the style!

[@mosesturner4018]

This is freakin awesome!! I'd been thinking about harmonic drives for like the last year and a half; this never even occurred to me!

[@DailyFrankPeter]

Very educative thank you. Good work with your design, too! It seems like a natural fit (harmonic drives being almost compliant mechanisms themselves).

[@safetyinstructor]

Appreciate the use of engineering units ;)

[@wobblyjellyman69]

Once again an original idea and a great quality video. Keep it up mate! Great stuff

[@KingdomOfHeavenPictures]

Wow, your videos have become much better since 2019. Great work!

[@MecheMike]

Great job! Keep developing.

[@KageBlink]

Thats amazing, I can see PETG or ABS making a huge difference in strength. I would go at it again, good video! Thanks for sharing

[@SianaGearz]

ABS/ASA are finicky but they could work indeed. PETG only works up to a point, under repeat stress and certain applications of force it paradoxically crystallises and becomes brittle! But there are printable TPU/TPE varieties, and not all of them are that low Durometer, they could be of use as well, they're basically made to handle repeat stress. Polyamides (Nylons) as well after one-time conditioning.

[@alinoori3350]

This was awesome I love to see an optimized version of it👌

[@swannschilling474]

I designed a backdrivable 40:1 Cycloidal Drive which I am super happy with...all my attempts to get a harmonic drive going failed terribly!! This is super interesting!! Keep it up!! 🤩

[@jasonorozco1587]

"It's not actually this bad, it's actually really good." Best disclaimer ever. Will keep that one in my back pocket. 😂

[@nikitanugent7165]

Very well done! I'm keeping my eye on this. I'm hoping to start working on a small robot arm soon, and this is definitely has potential.

[@SamAlderDesign]

Very clever, and clear explanation of the results. Appreciated.

[@AllanKobelansky]

Very educational. Well done Levi.

[@CoolAsFreya]

Can't believe this is the first time I'm finding your channel! This video alone has earned a sub! This design with a less brittle material for the compliant gear could be very good.

[@aditya95sriram]

The KZbin algorithm brought me here and I'm not complaining :) Good work!

[@damianbrisendine5154]

Super cool would love to see it scaled up and tested again

[@Molb0rg]

that is super cool, this is indeed how they have to be made. Very cool, thanks!

[@ArunUdai]

Awesome design and your research. Great demonstration 👍

[@deschoee]

Awesome! More compact, less parts and no imbalance.

[@svampebob007]

Hey if you want less "wobble" without over stressing the threads I would suggest adding some springs to the bolts. It does add "more load" to the threads at the same torque, but that also allows you to convert that load into frictional between the 3d printed part and the metal beam. This is kinda how we use springs on watercoolers for CPU's/GPU's, you don't want to crack the chip so you add spring loaded mounting brackets that distributes the load more evenly ensuring a "tighter" gap between the cooling surface and die... so in turns the force is applies more evenly. If you ruffen up the metal beam that would add more friction between the metal and plastic, kinda the opposite that we do with coolers. it's probably not going to make it "stiff" but it should prevent a couple of wibbly wobbly, timey wimey stuff to your presentation :)

[@ShivaprasadDabholkar]

Wow! Really enjoyed the video.

[@3DprintedLife]

Awesome video! I'm working on my own harmonic drive myself aiming to be super compact as well, but using an inside-out HTD belt instead of 3D printing a flex spline. Initial results are promising but I still need to get a high power motor driver and do some torque tests!

[@sephjfox]

looking forward to seeing another iteration of the design

[@red13emerald]

Love the idea! The geometry can definitely be improved, but this seems like a good start.

[@solosailorsv8065]

Rather DeVinci of you , Well Done ! Made of traditional spring steel, your flexure design is unique & novel

[@WungoBungo]

this is absolutely genius design. very well done

[@OpenSourceLowTech]

Swap in some spring steel strips with the PLA as just housing? Junior hacksaw blades are a good source of thin spring steel which can (usually) be bent 90 degrees without breaking...

[@alexkuhn5078]

Behold, a whole compliant CVT! I can't wait to put it in my Compliant Robin

[@i-make-robots]

nice! thorough! good work.

[@dythe7858]

So cool, hope I can learn to use what I learn at uni like you do. Best of luck making a reliable 3d printed harmonic drive. It would be fun to experiment and take your compliant mechnisum and extrude it on the y axis to add more torque but keep it compliant on the x and z axis. (Extrude the y axis until it's big enough to fill the empty space from the regular design)

[@stefanp7603]

Great engineering video!

[@user-bt2lx4gy7h]

Levi: I need a compliant mechanism that doesn't favor one direction The Compliant Mechanism: 🎶You don't know you're beautiful!🎶

[@keithduffield5239]

Thanks ever so much. Especially for your explanation and show and tell on how a harmonic drive works. I have used many HD's in steerable antenna, but never understood exactly how they work, despite trying.

[@SimpleElectronics]

Hey Levi, I love your content! Subscribed, keep it up!

[@christianmose9450]

Impressive! Harmonic Drives do fill a gap where hole bunch of alternative solutions should be possible..good approach!

[@artantme]

Man, congratulations! That's impressive. It broke on load, but it's just a trial and error process. Please keep on!

[@chrisBruner]

I've done similar things, with similar results. Hoping you come up with something even better. Good job.

[@theforcefor]

This is AWESOME!!

[@GabeIsko]

Cool Project! That's the tradeoff with Harmonic drives - no backlash, but your stiffness is compromised. Even happens on the indutrial drives. They are a lot stiffer than the plastic ones because they are metal, but not nearly as the stiffness you get out of a normal gearbox.

[@-powerband-gamer-6117]

You have a bright future ahead of you my friend.

[@leosbagoftricks3732]

Very interesting project- enjoyed and subscribed.

[@Lakitu1446]

I really liked this video, the way you explain everything and why you do it. That's the scientific approach i like to see with makers i like and subscribe for more, continue like that ;)

[@perpetualengine]

Great job man!

[@Gallardo6669]

Excellent video, thanks!

[@GlennLewis]

Cool design!

[@4KNoCopyrightMusic]

Your last video did great! Congrats!

[@NicAqueous]

Very interesting, good job!

[@emorag]

I'm here for the harmonic drive. More please. :-)

[@txikitofandango]

I don't know much about this stuff, but I found your video really easy to follow

[@asid61]

This is an excellent design! Those springs solves a big problem with printed harmonic drives.

[@julienboucaron9780]

Pretty elegant design. Curious to see what geometry, layering and other stuff you will create to put more springs and material to handle the torque.

[@DiekiKondrael]

I think the best bet is to use a more flexible material. With something like ABS or PETG, you could get the same flexibility from thicker (and thus stronger) parts.

[@kilianderoovere6272]

nice work!!

[@LeviDeHaan]

Great video, I'm gonna have to try making one of those.

[@gregarmstrong4653]

well done, you are really close to a solution, both the vibration and the strength. All you have to do is print the compliant mechanism seperate from the spline, print two, put one of them up side down and glue them both into the spline. Now the two compliment each other, and the mechanism should be much stronger and there will be less vibrations

[@Bigman74066]

I think that the curved part of the complient mechanism could be made thicker without compromising springiness. It may also be beneficial to use alternating left and right turning springs. Just a thought... Nice video! Thanks!

[@TheMadManPlace]

Not a "simple" concept but a very intelligent and eloquent solution to the problem - inspired work - congratulations. May I suggest movement limitation stops in the flexing wheel that will prevent the spring element from being overtaxed? This could cause lockup if the spring element is over-stressed but that is good - don't drive the mechanism beyond its mechanical limit. I wish that I could share a doodle here to visually explain what I'm talking about...

[@Name-js5uq]

Really liked it, the video.

[@josemq0x158]

bro, gran diseño, Really nice ! Saludos desde Peru

[@lukes_3d]

Man, compliant mechanisms and 3D printing makes such an interesting combination... I designed a compliant mechanism spider robot (you can check it out) and it's so fun! Great work and keep it coming :)

[@Decco6306]

To reduce wear on it, put petroleum jelly in it as a grease.

[@ares395]

That's pretty damn awesome

[@saxd0ct0r]

So I just discovered this video… fascinating for a non-engineer like me. My initial thought was that the compliant spine could be duplicated with the reverse orientation and combined. Therefore, when one is being stretched by the torque, the other is being compressed, and neither direction is favored.

[@poopypooppants4635]

Damn I couldn't care less about compliant harmonic drives but I watched this video in its entirety anyway. Cheers my guy

[@DIYwithBatteries]

You are a freaking Genius Broh... 😄👍

[@cobralyoner]

cool project!

[@curator23]

Awesome! I was think of trying this but haven't had time. Looks like you need to stiffen and shorten the compliant springs, and alternate direction like {. Would also like to see 3D printed raceways for the elliptical bearing. Subbed.

[@TheObstkuchen1]

Thank you. You saved my day.

[@fernandoi8958]

This is great design and video, congrats! Would love to see a metal version of this...

[@Untaramar]

great video! One comment, for those of us who are not in the know of what these sort of devices are used for, a intro of common uses or what you might be using them for would be spectacular. 👍

[@DEtchells]

VERY interesting! I’d definitely like you to pursue this further(!) What can be done to strengthen it (more torque), how stiff is it with the output properly attached to the moving spline, how much backlash is there, and how smooth is the motion? (Again, with the output properly attached.) I like this design a lot; I e seen other 3-D printed attempts at harmonic drives, but they’ve generally just mimicked the conventional design, with the moving spline being a thin shell. This looks to me to have a lot of promise!

[@ralphe9668]

nice work,

[@bennettslab2084]

Hell yes, this guy !

[@multiplysixbynine]

Nice work! This could really be a game changer with a bit more optimization of the spline geometry and material selection.

[@phillipnewman9174]

Amazing! Very well done. Just a thought... Perhaps you could have two spring mechanisms on top of each other, one biased clockwise and the other anti-clockwise. This way the overall mechanism would have the same torque capability in either direction. You might have to place some type of grease or thin spacer between the two springs to reduce friction.

[@emdo8437]

Great vid

[@mikebennett2015]

I used a harmonic drive back in the eighties, but it was different to the one you have. It had two outer gears, both same pitch diameter but one had one less tooth. The flex spline engaged in both the output would rotate one tooth for each rotation of the flex spline.

[@colbylippincott7173]

What if you replaced the longest section of each of those flexures with an off the shelf metal strip or wire or something? You could beef up the plastic sections and have all of the bending be done by the metal.

[@anoirbentanfous]

the solution should be from the design first before looking for the material science...

[@antno9158]

Surely design is interactive with material dcience? Different materials have different properties to design with. PLA isn't a great choice for a flex element.

[@revimfadli4666]

@@anoirbentanfous shouldn't you keep material properties in mind when designing? And designing for one material might not work for another

[@colbylippincott7173]

As long as you designed the mechanism to stay below the fatigue limit of the material, any material is a good material for the application. It all depends on what you are shooting for. If you are looking to minimize cost, but don't care about size, you could use a cheaper material and give it more room to flex without stressing the material much. If you care about size, but not cost, you could make it from a more expensive material that is better for higher stresses. And if you are really creative, you can come up with a design that optimizes cost, size, and performance using a mix of materials. Engineering should never be constrained to "this is the material for this application". That will severely limit creativity. Creativity, plus a clear, unrestrictive definition of the problem, the willingness to fail, and trusting but testing other's advice equals finding the best solution possible.

[@franciscoanconia2334]

That's a VERY nice design mate... The compliant cage makes it actually quite feasable to do in steel and just water-jet cut the middle. Maybe with a water-laser to keep as much material as possible.

[@traviscecil3903]

Would love to see you try this again. But this time, turn your spring. An inner core, an outer gear set, and two sidewalls with outward flex, but solid and without flex in the direction of motion. Think Goodyear tire. For bonus points, look up some of the solid tire concepts from Goodyear for the military.

[@stefanguiton]

Excellent!