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Wobble Ring Stepping Motor V2!!

by Ndrew, published

Wobble Ring Stepping Motor V2!! by Ndrew Feb 20, 2013
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This is a snap together version (some glue) of my printable motor. It has been shrunk and uses only 9 pieces, air pistons included.

The bellowPiston part is printed with no infill and needs to be airtight. When inflated it extends outward to push the glued on bellowLink part. The bellowLinks then push the wobbleRing, meshing with the drivenGear. Each piston is inflated and deflated sequentially to "step" the motor 4 degrees forward or backwards.

This thing is the successor to this:

And uses sgcg's fastener library

Also uses mechadense's epi-hypocycloids from:

The bellows used are modeled after this general shape:

Though I hope this latest version shows much improvement, I realize there is always room for better design. Please, chime in if you see room for improvement.

I also have to mention that I have not printed this yet, so I don't know if it will work. Of biggest concern are the bellowPiston parts, because they need to extend at least 2mm to be productive. I also don't know how easy it will be print 45 degree overhangs that are airtight AND slightly flexible.


All parts are oriented for printing without support.

Print 1 each of the following:

Print 3 of both the bellowPiston.stl part (without infill) and the bellowLink.stl part.

Open the bellowPiston parts at the top end by taking off the last layer.

Glue together the bellowPistons and bellowLinks.

All pieces snap together downward from were they are seen in the exploded view.

The wrsmAssembled.stl file shows the completed thing, minus gluing.

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Thanks! Just wish I could test the darn thing :P

Thanks! Just wish I could test the darn thing :P heh

I'm not sure I'd want to tackle printable pneumatics myself. I see huge potential for the solenoid approach you mentioned. I actually have some solenoids harvested from old zip drives that are roughly 4 cubic cm... perhaps a little large for the end goal, but perfect for prototyping.

If you really are dead set on driving the prototypes with air, maybe smooth rod sliding in printed bushings would give you a good seal. (I was thinking metal, but perhaps filament would be usable)

Yeah I don't blame anyone for not trying the print, will probably be an uphill battle. But if I can get my other thing working, the piezoelectric air valve, I won't need nearly as much current to drive it as solenoids.

If I do have to go without I think I'll try piezoelectric actuators directly, like this:

Here they are in action:

On the other hand, I've got some extra time if you want to send me the size of your solenoids I'll model a printable bracket for them. Probably have it done by tomorrow.

I'll need some time to dig them up and get the dimensions to you.

Also due to the way the motor works, I wouldn't expect much force would be needed and the solenoids could likely be operated well under their rated current. This might lend the design to be doable with home-wound solenoids which I think could be an important step on the way to building machines in the spirit of the Gada prize.

I'll try to include as much detail on the solenoids as possible as I expect the wobble ring can mate directly with the solenoids with minor modification.

Do you remember what brand zip drive they came out of?

Iomega external drives... I should be able to dig up the details for you tonight or tomorrow

... Sorry, tried replying earlier but clearly my comment didn't save :/

Turns out I gave the solenoids to a friend for another project, but I may be able to get some of them back... If not I'll look at reprapping solenoids for this motor.

I started to wonder :P
Right now I'm working on a gcode converter to polar coordinates for another project but after that I'm going to make a solenoid version that's parametric. That way anyone could test it.