The Wobble Ring Stepping Motor MK1
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Published on November 6, 2012
Derived from
Progressing Cavity Pump (cycloidical)
by mechadense
Description
Edit: This thing has been upgraded!
thingiverse.com/thing:52299
This is my humble start on an actuator that could be mostly printed on a 3d printer. Incomplete as it is, I thought I'd post it as it developed.
It is based on this:
act.sys.okayama-u.ac.jp/kouseigaku/research/okamoto_wobble_06/english.htm
Instead of air chambers, I plan on rolling my own solenoids, eventually.
It also uses hypo-epicycoidic gearing, based off this:
thingiverse.com/thing:28237
And it should move like this:
youtube.com/watch?v=UayBAHJQE_k
But instead the outer ring 'wobbles'.
The wobbleRing is 1 tooth larger than the drivenGear(51/50). This allows for 2.4 degrees between solenoid steps(360 / (50 * 3)). But that's with just one of the 3 solenoids pulling at a time.
Now why did I use cycloidic gearing? Well, I understand they wear a little slower for this application. Also I was really having a time getting the MCAD library to work. Please correct me if there is a better gear profile for this application.
I do also appreciate any constructive critism, as this is my first openscad project.
BEWARE: I have not printed this thing yet!
I really wish I could but I am still waiting for mine.
BEWARE: There be snakes in dem codes; look at the openscad code at your own risk!
I really do intend to add more paramaters too, just working out the basic form first.
Oh and for now there are no solenoids included. At this point I really don't know enough yet to design capable ones.
thingiverse.com/thing:52299
This is my humble start on an actuator that could be mostly printed on a 3d printer. Incomplete as it is, I thought I'd post it as it developed.
It is based on this:
act.sys.okayama-u.ac.jp/kouseigaku/research/okamoto_wobble_06/english.htm
Instead of air chambers, I plan on rolling my own solenoids, eventually.
It also uses hypo-epicycoidic gearing, based off this:
thingiverse.com/thing:28237
And it should move like this:
youtube.com/watch?v=UayBAHJQE_k
But instead the outer ring 'wobbles'.
The wobbleRing is 1 tooth larger than the drivenGear(51/50). This allows for 2.4 degrees between solenoid steps(360 / (50 * 3)). But that's with just one of the 3 solenoids pulling at a time.
Now why did I use cycloidic gearing? Well, I understand they wear a little slower for this application. Also I was really having a time getting the MCAD library to work. Please correct me if there is a better gear profile for this application.
I do also appreciate any constructive critism, as this is my first openscad project.
BEWARE: I have not printed this thing yet!
I really wish I could but I am still waiting for mine.
BEWARE: There be snakes in dem codes; look at the openscad code at your own risk!
I really do intend to add more paramaters too, just working out the basic form first.
Oh and for now there are no solenoids included. At this point I really don't know enough yet to design capable ones.
Instructions
Really none yet :/
I don't pretend to know enough to instruct anyone else when I've not built anything myself.
If someone were to print just one or two pieces, I'd think that the "wobbleRing" and the "drivenGear" would be the most illuminating. Really curious how they mesh IRL...
I don't pretend to know enough to instruct anyone else when I've not built anything myself.
If someone were to print just one or two pieces, I'd think that the "wobbleRing" and the "drivenGear" would be the most illuminating. Really curious how they mesh IRL...
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License
The Wobble Ring Stepping Motor MK1 by Ndrew is licensed under the Attribution - Share Alike - Creative Commons license.
Nice too see my epihypo function used for gears :)
IMHO I'd go for the original pneumatic (or hydraulic) drive.
I think you are losing the benefits of high tourque density by using electromagnets instead of air pressure
which is the main selling point of this device. (ratcheting will kick in way below structural strength of the teeth)
Solenoids as pulling magnets tend to have a very nonlinear force with airgapthickness which
(unless special purpouse rod pulling magnets are used) further reduces force density.
Also you'll need transformer sheet cut which makes it hardly DIY.
Shapeway's "StainlessSteel" (which has reasonable magnetic properties) might be a viable alternative
but with 10$/ccm its awfully expensive.
Also before beginning constructions an estimative quick feasability assessment
(= rough estimation of minimum force to expect for a given highly approximated geometry)
is always a good idea. If you really wanna do your own coils read up on magnetic Circuits.
The slight flexibility of PLA/ABS would lend itself perfectly for the original closed air-chamber design pictured at the okamoto website.
Still you'll need valves. But I think an appropriate cycling-valve which encodes the sequence in hardware could be printed.
with a sequence like this:
(o=ambient; x=closed; *=pressured) (ABC...chambers)
(Ao B* Cx) (Ao B* C*) (Ao Bx C*) (LONG - Ao Bo C*)
(Ax Bo C*) (A* Bo C*) (A* Bo Cx) (LONG - A* Bo Co)
(A* Bx Co) (A* B* Co) (Ax B* Co) (LONG - Ao B* Co)
If you'll add a hydrodynamic speed limiter (turbolent wingwheel) for a valve rotor that encodes this sequence you'll get a constant speed motor from a constant pressure source. If you want stepping control you maybe could use small low force (comercial) pulling magnets to control the valve.
As for the construction: Its a bit blocky.
Try to minimize printing volume by looking where no/little mechanical forces occur and take away as much material as possible. Example:
"frameStabilizer" takes no force => thinner
"solenoidAnchor" tips take lots of force => thicker
Try to minimize screw count by using plastic shape to reduce DOFs. Example:
The top and bottom plate are only this thick for the screws to go in sidewards.
Suggestion: make the "framesides" wider & THINNER and let them be vertilally hold by the "frameStabilizers" (make two dents ito them)
so you can use one vertical instead of four ratial screws.
I appreciate all the input. I have still yet to print this (printer on its way) so I do appreciate the feedback. Probably just saved me a version or two.
As for the solenoids, I won't be using them like you suggested. I do intend to keep designing with the goal of replacing a stepper motor, and so will be using something similar to your chamber sequence.
As for chambers, I was thinking abs would be better. Is it more flexible? Perhaps I could make them out of silicone once I print off a universal paste extruder.