3D Printed Cycloidal Drive V2 - Much Better!
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- เผยแพร่เมื่อ 27 ก.ย. 2024
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In my previous video I built a 3D Printed Cycloidal Drive which was relatively successful, although the cam snapped off under load and it vibrated a lot. This time I've balanced the drive by using two cycloidal discs 180' out of phase with each other. I've also made the cam shaft much thicker and robust by screwing an M4 bolt through the middle of it. This time it's much tougher, although we still need to do a lot of testing.
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XROBOTS
Former toy designer, current TH-cam maker and general robotics, electrical and mechanical engineer, I’m a fan of doing it yourself and innovation by trial and error. My channel is where I share some of my useful and not-so-useful inventions, designs and maker advice. Iron Man is my go-to cosplay, and 3D printing can solve most issues - broken bolts, missing parts, world hunger, you name it.
XRobots is the community around my content where you can get in touch, share tips and advice, and more build FAQs, schematics and designs are also available.
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@@occhieanimation2972 Plastics are hard to predict and tend to preform poorly under constant deformation.
@James Bruton The use of 3d Printed cycloidal gears is the focus of my undergrad research. I'd be interested in sharing my research!
Why dont you have a mount on the bottom where the plug in is and put a case thing on the spinning bolts that goes around the entire thing and make that a joint.
get an SLS .. that nozzled crap is really only for 3d illustration of prototypes
JAMES : "The cap fits perfectly " while he is just continuously hitting it with a screwdriver.
Those spacers need to be printed in red. Ask Ivan Miranda. He knows.
SPACEEEEEEEERS
Ivan would also approve of using a screwdriver as a hammer!
That's amazing. There is something really statisfying about seeing precision mechanical prints that work.
'Precision' isn't very applicable here 😅
@@xxportalxx. would you care to explain? :3
@@gokiburi-chan4255 it's made from 3dp fdm parts using bolts as axles... do I really need to explain the lack of precision here?
@@xxportalxx. but isnnt lack of precision in this case still a level of precision ?
i'm really asking honestly, forgive me for being an idiot.
@@gokiburi-chan4255 ok, see you're now mixing the types of speech, yes the noun precision can refer to any level of precision, however when used as a noun modifier it means that the noun being modified is precise. So if I were to ask what the precision is then yeah it can be anything and still be considered precision, however if I describe something as being a precision thing then it is by definition a thing that is expected to have a high degree of precision.
So by saying 'precision mechanical prints' it implies that the thing 'mechanical prints' is very precise.
But even without knowing all the grammer rules and definitions (which I certainly do not, english is a mess) you can simply note that colloquially saying something is a 'precision instrument' generally implies a high degree of precision (not a variable degree of precision).
Love the fact you're exploring cycloidal drives, and I mentioned it in the previous video and I'll mention it again. The gear you have is not a proper cycloid, if it was the bearings around the perimiter would be unnessecary because there should be pure rolling contact between the cycloidal gear and a circular pattern of pins to begin with (i.e. those bearings shouldn't be turning at all). This would let you shrink the size of the thing down, save weight with all the bearings gone and make it cheaper.
Second, you may or may not want to look into this, you can have the outer pins run free, if you fix/anchor the center pins so they don't spin. This might be handy since it moves the output to the outside perimeter. This means you can have the output supported between both ends, rather than cantilevered off the end of the gearbox which I think(?) you mentioned was a bit of an issues with the last design. Paul Gould here on youtube has some designs/videos with this configuration.
hope it does this, opendog v3 wuold be wasted with 15kgs of motors and gearboxes
I would definitely check out Paul Gould, James.
He was featured in part 1
Seconded. The current design is using an "ordinary cycloid" which is easier to derive in CAD but lends itself to higher oscillating forces across the assembly and weaker cycloidal discs; the proper/alternative cycloid is called a "contracted cycloid" or "curtate cycloid" and it greatly improves the vibration and strength while allowing for a smaller assembly. Google "contracted cycloid tec-science" for a fantastic discussion and derivation of the improved drive geometry with nice animations. It's not something that can be easily geometrically derived in CAD but there are functions and generators out there for use in solidworks and fusion. I'd include links but youtube ate my last attempt to write this comment. :\
@@kimtae858 This is how I designed my cycloidal gearboxes and it is actually quite easy. th-cam.com/video/Nk3aaVcvbpA/w-d-xo.html
James: "I made a leg that hops to test shock loading."
Meanwhile the neighbors: 😳
A robot that gains you some street cred... nice.
scale that shit up into the Wrong Trousers is what I'm saying.
use those fiberglass rods that they put in jumping stilts or something instead of that aluminum. hell just mechanize the jumping stilts so they fold up on the back of your calves.
.... you know what? imma do that.
@@kingmasterlord DUDE POST THE LINK HERE PLS!
This is rev1
@ 6:04 - Every tool is a hammer ~Adam Savage
I've bapped some stuff in place with power tools definitely not designed for it.
I mentioned this in the last video, but there's a variant where the outer housing rotates and the cycloidal disk(s) only wobble (but don't rotate). Since this is intended to be used as a shoulder or leg joint you would be able to print the armature and the outer housing as a single piece. This would seem to have some benefits in weight, overall size, and reduced side loading of the bearings in the whole leg.
Also It looks like you have some space between your cycloidal gear and your bearing surfaces (both inner and outer), which is almost inevitable with 3d printed parts. In a perfect world the cycloid would touch every bearing at all times, and would not have any slip contact with the bearings (which then wouldn't turn). In the real world only a few points will contact at any one position, and you'll see some slip contact with the bearings (which is why they are turning slightly). If you continue using the bearings, consider a compliant membrane (rubber bands?) around the bearings. This will probably quiet the mechanism significantly as well as ensuring all the bearings share the forces, instead of one or two at a time.
this
lol do you mean harmonic drives?
@@qwertzuiopqwertzuiop2107 harmonic drive would be a better idea
@@qwertzuiopqwertzuiop2107 not at all. I dont advocate harmonic drives for this application because they are rarely back-driveable
I just found your channel yesterday from the Cycloidal Drive v1 video and subscribed. Needless to say, I am thrilled with your timing.
That looks very nice. You could concider brass inserts insted of roller bearings. Friction will be just bit bigger but you can significantly reduce diameter and mass of drive. (estim 50%). As well just as recomendation for knee joint to use smaller motor and drive as torqe will be much smaller on it. so again you can save some mass.
Brass inserts are fine between two harder surface. they would cut into the soft plastic too easily.
@@hzmeister9596 Not necesery. First of all sliding will be between Bolt and Brass insert. Plastic will be still working as it is now. But totall mas will dropp down significant.
@@mariuszhoscio870 I disagree. Bronze bushings are never used like that. There’s way too much friction and the point load of the smaller diameter would make it even worse.
When he was trying to stop the arm with his hands I was terrified 😳
"It would probably take my fingers off it I wasn't careful..." Proceeds to stick fingers near pinch point.
All this professional production and the man is using a screwdriver as a hammer
have you thought about using a single cycloid with an off-center mass to counteract the vibrations, i have some ideas to make it pretty precise, also please look at the comment that suggests to use mathematically calculated cycloids that wouldn't slip on the exterior and probably could work witout the external rods with bearings or spacers, it would really save lots of weight and would be an interesting development, i think that mostly on the knee joint, witch will be a moving mass, the weight of the assembly w, ould be strictly related to the mobility of open-dog, i really believe in the project
This is interesting. A mathematically correct cicloid should not rub and would allow to decrease the outer weight of the drive, making it more inertial friendly
@@Otakutaru great point
This is a common solution. This is the design I'm currently testing in my research.
I think doing a non-symmetrical infill could offset the balance of gear
Some thoughts. Using dual cycloid offset by 180 degrees not only reduces vibration but also increases the strength of the gear. Strength is not always an issue, but given the high impulse load that using this to drive a leg joint makes me think it might be important, especially as it is being made out of PLA.
And as for using off center mass to counteract vibration it seems to be pretty hard to achieve this with a good precision. Besides this has to work at varying RPM, not just at a specific speed, which makes it even harder to accomplish. But I'd be very happy if I'm proven wrong about that. Also where does the vibration really originate? It would seem to me that the high frequency vibrations is probably coming from the center cam as that rotates at the motor drive speed. The cycloid disk will oscillate at the same frequency, but rotates at one tenth the speed. It would be interesting to see a frequency spectrum breakdown. There should be spikes at engine RPM and at RPM/10. Question is how large these spikes are.
Off center mass can be used to dampen the vibrations caused by the cam, but vibrations caused by the cycloid disk oscillating can't be countered as easily. Again, I would be happy to be proven wrong.
To switch things around some, a single cycloid disk version should be more energy effective than the dual disk version. Less weight, smaller contact surfaces and less bearings do make a difference.
I am a homeschooler, but I have a coop on Tuesdays that starts early. Every Tuesday morning, I make it a priority to watch your new videos before I leave for school! Thanks!
You are absolutely a gem for releasing these files as open source. Do you have a bill of materials for the bearings?
Hey James! Loved the video. Just a thought for the final build, you should look into precision shoulder bolts... They have a precisely ground diameter and a threaded section on the end. Should work really well for a bearing fit without much redesign. They're not too expensive either. Cheers!
I Seriously think this is one of the most underrated science-mechanics-robotic-tech stuff in youtube.
Been following since you were 23k subs James and you were doing the First Iron man stuff. Such a great channel. Thanks for existing and creating all of these videos.
AGS Door Ease Lube Stick is a very effective lubricant for plastic-on-plastic parts. Just apply like a crayon onto the 3d printed parts and exercise the joint. In a few motions it is super slick without the liquid residue. I simply don't use oils or greases any more on 3d printed parts.
woulnt graphite just work as well?
Yes, but very messy. The Door Ease is clear and odorless.
You might have seen this before but the VESCs are able to connect to hall effect sensors for positional accuracy if your motor has them. It solves (or reduces) lots of the issues with stall torque and can safely dump a lot more current in at low speeds
An simple trick to increase layer line strength is to just print at an angle. Even a slight angle will help. With some of these parts that are held on the inside of a bearing, you could put a flat spot on the OD of the part and print it on its side as to not use any support material.
Another easy trick is with counter sink screws. If you use a hand drill to spin the screw fast in the hole before assembly, you can friction form the counter sink to the shape of the screw. This not only more evenly distributes the force of the screw head to the plastic but also bonds the layers in the countersink together better. Also, this helps when you don't know the dimensions of the screw head. (some) Wood screws have a compound angle on the head and instead of trying to model it perfectly, get it close and melt it with friction the rest of the way.
If you were to make the assembley water tight, you could fill it with oil to lubricate everything nicely, and ensure slippage between the cycloidal discs.
Very nice! That looks much smoother and more durable than the last one. I still think that if you made the outside of the disks slightly concave and the outside of the bearings slightly convex that you would get a smoother transfer of power. A) It would make the disks self-centering; reducing wobble and vibration. B) It would reduce side-load on your bearings; increasing longevity and reducing friction. C) It would spread load over a larger surface area; increasing longevity of the disks. Also, maybe a grease channel in the center of the disks to hold a very small amount of lubricant?
The VESC does have hall sensor ports and can handle encoders like the AS5047 - not sure why the motor driver was blamed so much.
This is some pretty good engineering. I wish my body was still able to handle doing the things my mind can come up with. It is nice to watch videos of like minded individuals like yourself! Thanks for the wonderful video!
Bushings would be a good replacement for the bearings.
Yep, probably Nylon ones like I mentioned
@@jamesbruton hey now. Are you familiar with the work of Buckminster Fuller? He really did do a lot of thinking ahead of time...
Almost 1m subs. Its been a crazy durney watching your progress over the years
Gosh James.. You are so brilliant my man. I'm going to join your patreon. Enough following you behind the scenes.
If you put lips on the cycloidal gears, kind of like the flanges on the side of a timing pulley, then they would self center on the 11 little bearings. This would help the 2 gears not rub on each other.
alternatively maybe use bearings with snap-rings built in to hold them centered?
You can attach three hall effect sensors to the VESC, and just glue them near the motors magnets. Impressive design! I think not having bearings would be a mistake. Rolling friction is in a whole different ballpark than sliding.
This is your next generation of actuator!
just writing to let the YT algo know how awesome is ur Channel 🔥🔥🔥
VESC can use Sensors and the newer firmware version also have HFI that allowes you to start pretty good even without sensors. Its still probably not the best controller for your application but if you configure everything properly it will be a lot better than in your current test.
Yep not sure if HFI would would work on a motor like that but is worth a test! It can use many encoders as well.
Even if I don't know about things in this field its still really interesting to see. That's a cool gear box.
I was expecting the table legs to break while testing the torque
hmmm, i might replicate this design for a compact hand crank reduction gear box for a cardboard, paper, plastic, ect shredder. would certainly be cool
I love it, glad u got part 2 so quickly after the first one. Also i believe you should lubricate that gearbox A LOT more. A LOT A LOT more
I don’t think so; rctestflight needed to lubreacte his a lot because he had plastic on plastic for the gears, but this one only has roller bearings on moving surfaces, so it doesn’t need as much or any, for that matter.
I cannot overstate how impressed I am with this - it brings me great joy to watch this
The 5 holes in the cycloidal disk could be lined with high tolerance metal rings instead of bare plastic. This could massively reduce wear and tear and also allow you to more tightly control the tolerances to reduce backlash. Just a thought! Looooving this project!
oilite bronze bushings would also be good to replace the small bearings as they are ideal for low rpm high load applications and are self lubricating
Armchair engineer here (in other words, zero knowledge). With regards the discs rubbing together, could you add some recessed
ball bearings between them? I guess though it could cause wear and tear as well a little flex.
That's well engineered! This video (especially after having seen version 1) is "very satisfying." lol
Hey if you are still using your cnc machine I would recommend that you submerge the cutting bed fully in water to help disperse the heat and to help with the lubrication and the particulates.
Molybdenum grease is incredible, double the lobes, no rotary bearings just double metallic sheet between could have an optical gradient for position, halves the size using a stronger substrate.
I'm really impressed with what you have done here. I have done a modest dive into the cycloidal drive system. I have come to wonder if it might be better, for the drive/reduction to be in the pulley. Reasoning that even industrial robots use the belt drives to creatively position the motors. As you mentioned, if tension-ed correctly they have incredible holding power and minimal backlash. This also provide modularity to the system; a motor, pulley or belt can be changed without removing and disassembling an entire sub-assembly. Therefore; I postulate that building the cycloidal reduction into the pulley and retaining the belts is going to be your best approach.
This new motor design is fantastic. Doing two internal gears to reduce vibration is genius. I am excited to see what version 3 looks like, i predict getting rid of all the crazy drives is going to allow you to make something super sleek!
to space the two drives apart from one another and casings you may want to look into replacing the bearings on the center shaft with ones with a cir clip grove in the outer race or a shouldered bearing.
Thank you! This is very good starting point for further improvements!
12:59 the robot is vibin'
Another episode of watching James narrowly not breaking his wrists or cutting his fingers off D:
I think he will @ V3 :/
5:04 -- How my brain feels when trying to follow every detail of these builds.
Great job on the design. Thank you for sharing with us.
Hey James, I'm gonna put this on my large format 3d printer. Love what you've done here.
If you use HFI sensor mode (High Frequency Injection) on the ESC (Technically it's not a VESC if it's not manufactured by trampa), it will actually outperform hall sensors, and have great holding torque at the expense of noise. However HFI is picky about what motors it will run on, it's pretty good on skateboard motors, but useless on hub motors, and yours seems somewhere in between. Oh, and HFI is only available for FOC mode, which supports encoders as well.
hehehe I see you
and also, HFI can be tunned, but that is a hella ride :D and when it does not like something, the noises it makes...
I just noticed that James had almost 1M sub ^^ it goes so fast, the last time I remember he had 150K and that was already impressive. Good Job, continue hard work 😉
I read that having only 2 discs is not enough to cancel all vibrations. But adding more out of phase discs adds friction. So only good at low speeds.
cycloidal drives offer more reduction in a small package. he's using a 5:1 reduction and could probably get away with a belt which would be FAR simpler with a belt, and zero backlash too. I made a 30:1 drive that's smaller than what he made (using two for a satellite dish rotator)
It would be pretty easy to 3D print bearing "replacements" for the outer ring of bearings, just to test it. Since they are turning very slowly I would thing lubricated PLA wold be fine for the job, as there is a fairly large contact area between the cycloid gears and the rollers.
Probably, I'd quite like to find something off the shelf though.
Amazing work. Beautifully build
Nylon rod on a lathe to machine down to precise diameter and replace all of the small bearings with cuts of it, using lubricant of course. You could embed bushings in them to sleeve the bolts to further reduce friction and wear.
It's so cool that you're making a cycloidal drive at the same time Levi Janssen is making a harmonic drive. They are very different approaches to the same problem, compact gear reduction, and I'm interested in seeing how they compare. It seems like the harmonic drive has a larger reduction and might not be as easy to backdrive, but it looks way more compact and is simpler to make.
no need for odrive, vesc can handle foc bldc aswell. vedder even works on a way to measure the motor imperfections with current pulses into the coils of the motor, so that afterwards he can use the floating coil as kind of a hall sensor itself. this guy is a genius! also nice video btw, really enjoyed.
Printing the whole thing in Nylon or some other hard wearing filament (igus filament, Ninjatek Armadillo), and packing it with some heavier grease will do a good job in reducing the parts count. Potentially using some liners and bushings instead of the large section bearings well might cut down on the cost without compromising the accuracy and strength. Bearings are great for higher speed, but aren't as necessary for low speed applications like a robot joint.
Seeing James Bruton grab the bar rotating bar makes me think hes lucky to still have all his fingers parts.
If he had kept holding onto it for too long the bar would have slammed his hand against the 2x4 and he could have seen how much damage the shearing action would do against his hand.
If your doing stupid crap, plan it so that when eventually you screw up you don't pay too steep a price.
That asynchronous and continues motion of gears is troubling my brain, but it looks mesmerising.
Great design. Just a thought: If you're just testing the gearbox, why not just take the motor out and lock the motor input. Then you can put torque on the output until failure.
you could put a lip on the top disk to be supported on the outer race of the bearing.
The rate of you producing content is amazig!
If there's one thing ive learned from watching Black Mirror, it is: dont mess with the robot dogs
It seems that, with a little further iteration and refinement, this would not only supply inverse reactive current for use in unilateral phase detractors, but would also be capable of automatically synchronizing cardinal grammeters.
Nice work James!
James you could use the igus plastic sleeves in the place of the small bearings.
fantastic work! I did not think the offset would be enough but it seemed to work!
Try enabling HFI on the vesc. It will track the motor perfectly, although it is a little noisy.
The vesc can also use an encoder :)
Hey James, I have been following your work and gotta say I love the videos and all the progress you've made. Also Have you considered the harmonic drive for the reduction? I am sure you already know about them, but they are widely used in robotics, very relyable and lighweight, and straighforward simpler for some joints. Sorry english is not my first language. Good luck with the channel and the proyect dude, you are nailing it.
I miss the 3d printing music :<
Also fuuckk please don't test its power by grabbing these screws, Im afraid you can break your fingers.
Anyway
Great vid
"Can't stop it with my hands"
I'm afraid it might do the same when his hand gets stuck.
Bones are roughly the same strength as wood the same size, your fingers are about as strong as a thick pencil.
James you should turn that motor into a 10 piston air engine (to also counter act to wobble like a traditional engine)
Could you improve on the single cycloidal design by adding a counterweight instead of a whole new cycloidal disc? and also improving on the strength. This would keep the weight down by a huge amount - half the bearings, but still the same weight from the weights being equal to that of a second cycloidal disc
Yes, this is a common solution. This is the design I'm currently testing in my research.
10:00 It's perfect. It whimpers like a dog.
Hey James, Firstly just wanted to say, I love the videos on the Cycloidal Drive, really interesting to watch :) Next I was wondering if this kind of gearbox would be scale-able?
I think you might like the pricing and lead times of MJF PA-12. Sure you can print everything yourself but that costs time and PA-12 parts have higher tolerance and are 12ksi YS. It will be the better option when you want to make 8+ gear box assemblies all at once. Offloading some printing time would reduce your time to make revisions and let you focus more on content creation. The cost of MJF parts greatly decrease as quantity increases so maybe it's something to check out when you're done prototyping one offs and are closer to a final design.
5:04 - the movement reminds me of a twin rotor engine
good job! that motor is a beast!
Maybe just a thin nylon sheet between the discs and delrin bushings instead of the bearings. IIRC, you can get self lubricating delrin bushings.
That cycloidal drive looks even faster then the last one and I'm really sure that would produce a lot of thrust if someone attached a propeller of the right size to it and it might even have the potential to produce enough thrust to propel a paraglider.
Like in previous video, your printer seems to be heavily under-extruding, those large gaps especially on top layers are good indicative of that. That makes your parts also weaker as the plastic doesn't melt together so well. Fortunately that can be tuned from the control board without any extra cost.
Looks like your table was ready to give out before the drive. Pretty impressive, especially considering it's all 3D printed parts.
One could use the up and down motion of the inner gear to build a linear drive that runs in parallel to the rotary drive
Imagine machining a clear housing for this😍
A vesc is actually capable of running a bldc motor with a proper encoder. You can use hall sensors for example.
That is really impressive! well done :)
I always enjoy watching your videos. Thank you for making them.
The motor spin at 3:40 looks like the shaft is ever so slightly off axis. That could be part of the left-over vibration
I once had a cyclo drive where the profile of each of the two cyclo wheels was the xor of two cyclo wheels where one was turned by half a "tooth". If I remember correctly, this doubled the contact points
Yet another project that makes me want to get a 3d project. Hahaha, awesome!!!
Do you have a standalone Bill of material ? I want to price those bearings on aliexpress, 100 british pound seems very steep for such cheap mass produced bearings
this thing seems strong enough to operate a cable and pulley system for powered cosplay puppetry.
Maybe you could use some steel dowel pins instead of bearings along the outside to cut some cost while still keeping friction down.
Yesss!
This is really awesome.
I definitely like the idea of nylon to replace the outer bearings and get the cost and weight down etc. Look forward to seeing it on openDog
pretty cool. you could make it stronger and give it less slop if you made it out of cnc milled aluminum, too.
Very interesting drive reduction. For the flat parts, you may want to consider milling them from expanded PVC. (Presuming you have a CNC mill... I don't know... first video of yours that I have seen.) A sheet of 6mm expanded PVC is not expensive , it is durable, and quite easy to machine. I use it for a great many things.
Thanks for this love seeing diy robot dog
Amazing work. Great job.