3D Printed Cycloidal Drive V2 - Much Better!
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- Опубліковано 28 бер 2021
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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.
Previous version: • Experiments with Cyclo...
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Former toy designer, current UA-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. - Наука та технологія
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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.
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
“They’re actually slightly out of phase with each other, by 180°” 😂
I think the cycloidal disks themselves are only 18 degrees out of phase with each other (ie, the angle between two adjacent lobes). But the center cams they're mounted on are 180 degrees out of phase.
That's less than 540
@@steveman1982 if something is more than 360 you can subtract x number of 360s and have the same offset so a phase offset of more than 359 doesn't make sense a 360 degree offset is a 0 degree offset when it comes to phases/relative position of peaks. I could be wrong but point me at something explaining what above 360 degree out of phase would mean
yeah, each nub is only 18 degrees out of phase
@@ShaunHusain That's the joke lmao. Outside of explaining phase (which is really -180 to +180°), having a value above 360° will tell you how many rotations PLUS the offset something has compared to a reference.
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!
Ah yes, my life savings worth of bearings
Jesus dude, calm down the flexing. I only have so many girls you can steal.
Just buy em bulk my man. They are cheap as shit in bulk like 10 cents per
@@rrtsduf do you have any good sources you use for bulk bearings?
AliExpress is great for that kind of thing
A cheap source of bearings is fidget spinners
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).
@ 6:04 - Every tool is a hammer ~Adam Savage
I've bapped some stuff in place with power tools definitely not designed for it.
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. ua-cam.com/video/Nk3aaVcvbpA/v-deo.html
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.
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.
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!
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
This might be the coolest concept, execution, and overall video I have seen in a long time. Captivating.
Gosh James.. You are so brilliant my man. I'm going to join your patreon. Enough following you behind the scenes.
James, i just wanted to thank you for your work! I am currently not in the financial situation to support you, but when i am, i want to do it! Because its fantastic that you publish a bunch of your incredible work open source to work with. Thank you so much!
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.
This has been very informative. Thanks James. I'm working on my own robot, and this tutorial has given me some new ideas.
I'm genuinely loving this project James, keep up the hard work!!
Super cool! Can't wait to see version 3 with nylon rings instead of bearings.
This is a great project and this gearing system is really cool. I'm really curious to see where this project goes. I'll probably check out your previous videos soon, and I just subscribed to see the development of all of this :D
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?
Hey James, I'm gonna put this on my large format 3d printer. Love what you've done here.
Excellent improvements! The 180 degree out of phase worked great! Looking forward to a complete legs setup and test!
I cannot overstate how impressed I am with this - it brings me great joy to watch this
Killin it lately, James! Love this stuff.
Almost 1m subs. Its been a crazy durney watching your progress over the years
Great work brother! Love seeing your work
Amazing work. Beautifully build
hey james, just want to say your videos and projects are super inspiring and waiting for your upload is one of my weekly highlights, thank you for all the amazing work you do!
thanks!
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!
Thank you! This is very good starting point for further improvements!
Would be cool to see a v3 with nylon bushings instead of bearings, but they would probably be better of turning on a smooth rod than a threaded rod
fantastic work! I did not think the offset would be enough but it seemed to work!
Great job on the design. Thank you for sharing with us.
WOW, great video and project. You are a Master! Thanks for sharing.
Interesting application. You could add bearing tracks to each cycloidal disk that would allow for adding individual ball bearings (also nylon or ceramic?) and would also serve to space the discs apart; thus reducing contact area and friction.
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
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.
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!
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?
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.
Nice work James!
just writing to let the YT algo know how awesome is ur Channel 🔥🔥🔥
Even if I don't know about things in this field its still really interesting to see. That's a cool gear box.
I use VESC with hall sensors or a AS5047D encoders all the time.
With an AS5047D the VESC supports position control, too.
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.
Great design and nice improvements over V1.
thanks, more testing coming up over the next few weeks.
@@jamesbruton What are your thoughts on having three disks? Is your design rigid enough to have the output on one side as opposed to both sides of the gearbox?
The rate of you producing content is amazig!
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.
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 always enjoy watching your videos. Thank you for making them.
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!
James Bruton, You are a real life Stu Pickles. Really loving your channel!!
Amazing work. Great job.
That's well engineered! This video (especially after having seen version 1) is "very satisfying." lol
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
Excellent work!
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.
Nice work! What a design... But very interesting to see the upgrade compared to the last time ;)
good job! that motor is a beast!
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.
This is starting to look super promising! Another alternative to the bearings might be bronze bushings. Could probably be fashioned out of some bronze pipe or whatever that's available at a local hardware store for plumbing, though their inner diameter might be too large. Nylon would certainly be better for weight reduction, but I'm sceptical about their endurance (based only on gut feeling, to be fair). With either you could try making the cycloidal disks either thicker or thinner. I wonder how it'd hold up with less or more surface area, especially once you work on opendog v3 where you might want to have the knee joint be a thinner design than the hip joint or something like that.
I was thinking just make the entire thing smaller. It looks really solid already. If there is a problem with structural integrity for a smaller version, just try a stronger material.
That's some serious designing
great work and presentation
Great improvement sir!
Awesome video! I hope we get to see this with an ODrive or other feedback motor controller!
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.
That is really impressive! well done :)
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!
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.
Hi James! Have you heard about the abacus drive? in theory it has great backdriveability and should offer a little more compactness along with efficiency if done well.
this is the best video yet that ive seen on cycloidal drives.
This is a beautiful project.
Well done so far. The next step is to test till destruction, and identify the weak links, Im guessing the central cam shaft pieces. For these you could make a mold from the 3d printed parts in silicone, then cast two part polyurethane copies of the original ( pick a material in the 65-75 D shore hardness range) hexcel modipur. In fact, if you need to make several of these, you could just make a mold set for all of the parts. The good thing about this is that you can re-inforce the polyurethane with chopped strand fiber glass, or carbon fibre / mineral filler. This tech is a perfect fit for the type of prototyping you do
I just kept saying "that's fucking awesome" over and over during this video.. amazing work.
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?
PLA is probably the best choice for gears. Because of its hardness and also because its very smooth. ABS is maybe more heat resistent but because it is more flexible and not as smooth (still very smooth), also would generate more heat.
I was expecting the table legs to break while testing the torque
I love your engineering! Keep it up :D
Holy shit. That is some really impressive engineering for an "amateur" (and that is a complete understatement when describing your eclectic skillset) fabricator working out of your spare bedroom. Well done.
just awesome keep up the great work
Hey JB nice bit of work really like your ideas keep up the great work chap 👍 good vid also hahaha 😝
The large spinning mass of the motor seems to create a lot of inertia at the output. That might be a problem for using back driving as a a spring.
Thank you for the work.
Nice work! Maybe you could have a look at strain wave gear / harmonic drive reduction? Not sure how feasible it would be to make but it might reduce the size and weight of the gearbox
Yep next week!
@@jamesbruton Ah excellent!
@@jamesbruton Have you seen the Abacus drive from SRI?
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.
James you could use the igus plastic sleeves in the place of the small bearings.
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
The VESC does have hall sensor ports and can handle encoders like the AS5047 - not sure why the motor driver was blamed so much.
you could put a lip on the top disk to be supported on the outer race of the bearing.
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.
Have you considered replacing the smaller bearings with 3D printed rollers on metal pins? Might help reduce costs if it works.
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.
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.
This is your next generation of actuator!
Amazing engineering.