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I'm considering building my own b/c axis. The Doughty drive is great, but I'd like to be able to use a larger motor. New harmonic drives are well over $1k each so I'm stuck at looking at ebay. I stumbled on this set. Would some one help me figure out if this would work? I figure the center piece goes into the piece on the right. Where does the piece on the left go into? How would I go about attaching a stepper motor to something like this?
Thanks in advance.
Jim.
I believe the piece on the left (wave generator) goes into the piece in the middle (flexspline) then they both go into the piece on the right (circular spline). Motor attaches to the piece on the left.
Have a look at this [nomedia="http://www.youtube.com/watch?v=BjXNI-AEpRA"]YouTube - Funktionsprinzip: Harmonic Drive Getriebe[/nomedia]
Thanks jjacstcy. Great video. Though I still have some questions.
1. with this unit, how does the motor shaft get coupled to the wave generator?
2. I assume the piece that I'll be rotating with this unit fits onto the middle piece, how much weigh can it handle?
I am no expert but I think there is a piece missing. There should be a piece that gets pressed into the wave generator, that is where your input shaft goes. Your output shaft connects to the circular spline.
Or you have to make that missing part by yourself :)Quote:
Originally Posted by jjacstcy
Also what's the max. input RPM for such an transmission?
Its a hollow shaft unit. Hole is for wires or piping to go through.
How much weight will it handle?
None, its a component set not a mounted unit. You need to build your own housing, mounts, and support bearings.
Google the Harmonic Drive website and download the catalogs, You'll find mounting examples and engineering info there.
Bob
Thanks for the advice. I've browsed through the catalog, but can't quite understand how to mount and drive these things. I've decided to buy a couple of different types to learn on. Luckily they were not too expensive. I'll probably have a million more questions once they arrive.
Thanks again.
My ebay harmonic drive just arrived. There is significant resistance and cogging when I rotated the drive. Is this normal or is it supposed to spin like a ball bearing?
I don't believe that is normal. My two behave more like bearings, like you mentioned.
HereinCS-
It should rotate freely. It is likely that you HD unit is in a "Dedoidal" position. Take a look at page 12 of this PDF for an explanation:
http://www.harmonicdrive.net/media/s...hg-catalog.pdf
You should simply remove the ball bearing piece first (the wave generator), the remove the flexible spline from the circular spline. Replace the flexible spline into the circular spline making sure that there is equal clearance on either side. The flexible spline will only engage the circular spline at the maximum diameters of the elliptically shaped wave generator.
While you have it apart, you could clean the teeth, clean the ball bearing, and re-grease ti with fresh grease to ensure that there aren't any particles of stuff in the bearing area.
Keith
Thanks for the advices. I think I had it a bit off center, it's rotating more freely now. I still feel a bit of cogging, but it's not too bad.
I guess my next question would be how do I mount a table to it without the gear falling out?
You need to have external bearings and a housing to take the load. The drive only creates torsional stiffness - it is not intended to handle any other loads, and only will work properly when contained in a properly designed housing. You will need to look up the mounting info for your particular size, design and manufacture a housing to fit it.
Keith
Thanks. I think that this b/c axis is project is now way beyond my scope. I have to settle for a smaller motor and use a Doughty drive after all. Any one want to buy 3 harmonic drives? :(