Stepper shaft couplings - can you ID these?

[John S]

Jaw couplings are crap. They are designed for shafts that are out of line in one axis, not two axis as often happens in home built machines.
Any out of alignment takes up power to correct, run one at say 10 degrees out and see how hard it is to tun and what heat is generated.
now transpose this into two axis and that creates problems. Jaw couplings or Lovejoy couplings to give them their correct name are not designed for zero backlash, they might be well made but they are not guaranteed to be zero backlash.

The only type of drive that can handle miss-alignment in two axis is the Oldham coupling

[Jonathan]

The only type of drive that can handle miss-alignment in two axis is the Oldham coupling

Looking at the specs Oldham couplings tolerate a surprisingly small amount of misalignment, not that that's a reason not to use them since you're doing something wrong if you can't get the shafts close enough...

Timing belts / pulleys are clearly the best solution for driving ballscrews... numerous reasons, but that's not really relevant here.

Hank, if you'd like me to make the part and can send me the drawing by tomorrow morning I should be able to fit it in. I've got plenty of aluminium bar, lots of sizes up to 3.5".

[John S]

Looking at the specs Oldham couplings tolerate a surprisingly small amount of misalignment, not that that's a reason not to use them since you're doing something wrong if you can't get the shafts close enough...

Get your head out of theory spec sheets and into real life.

http://www.youtube.com/watch?v=utEKKox2WHA

True you should get them bang on, not close enough, 10 thou out is as bad as 100 thou out.

[Jonathan]

Clearly the allowable misalignment is inversely proportional to the speed...as you said in the previous post misalignment absorbs power from the motor, in this case through friction. Since steppers are, relatively speaking, such low power motors this is obviously bad, even if the coupling does tolerate it in reality. I'm sure the manufacturers are conservative with the ratings. Hmm, I'm stating the obvious now, tend to make my own anyway.

This is much more interesting:

http://www.youtube.com/watch?v=G2DU1...ture=endscreen

[HankMcSpank]

Help, my "can you ID these couplings thread" has morphed into a fledgling technical debate" :-) (there must be something in the air around these parts?!)

Thanks for all the input...I guess the answer is "no, you can't buy 'em"...so when it comes to it, I'll have to get a better one made than the one I made myself......I'll limp on for now as it does work.

Thanks for the offers....I'll take one of you up on it when I get past my "make do" phase (which - using past history as a precedent - this phase will last far longer than it ought to)


Next question....where do you go to get a heap of 1.6mm thick mild steel in small rectangles made? (something like 4mm x 7mm x 1.6mm) ...I've looked in the local rag, but there's no "Small steel rectangle makers" in there!

Or if you were faced with having to make a few hundred....how would you approach it?