Flexible Coupling

I'm looking for a flexible coupling to go from a standard Nema stepper motor to a M8 threaded lead screw.

Any suggestions for a cheap solution as purchased joints seem to be a little expensive.

Have any of you had any success with flexible pipe etc.

... i used pneumatic tubes for coupling 5mm shafts to M5 threaded rod ( [forums.reprap.org] ), but you need something what's spanning between 7-8mm for the threaded rod and the much thinner motor shaft.

Maybe you can atach an adapter from the shaft diameter to 7.5mm ... or grind down the end of the M8-rod to the diameter of your shaft - then you can use a semielastic tube too ...

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Viktor
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Put a small gear on the stepper to bring it up to ~8mm and then use a short piece of plastic/rubber tubing of the proper size such that you can force it onto the gear and M8 screw.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
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I use vinyl tubing as a connection as mentioned. It fits really tight over the lead screw, but loose on the motor shaft so I use a hose clamp on the tube over the motor shaft. Works great and is extremely cheap.

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Thanks for the information. I think the plastic tube (Maybe with a little collar in one end ) looks just the job.

rhmorrison is good at this. usually we use the unstandard coupling like this. make a sleeve for a big size coupling ourselves. but the coupling and shaft gap can not too big.

you can get the 8mm shaft coupling here: 8mm coupling

-leso


VDX Wrote:
-------------------------------------------------------
> ... i used pneumatic tubes for coupling 5mm shafts
> to M5 threaded rod (
> [forums.reprap.org]
> -5732 ), but you need something what's spanning
> between 7-8mm for the threaded rod and the much
> thinner motor shaft.
>
> Maybe you can atach an adapter from the shaft
> diameter to 7.5mm ... or grind down the end of the
> M8-rod to the diameter of your shaft - then you
> can use a semielastic tube too ...

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Buy Coupling from China
Flexible Shaft Coupling, Jaw Plum Spider Coupling, Encode all on here
[www.fscoupling.com]

I use two sizes of vinyl/PVC tubing to create a very functional Z-axis coupling on my repstrap, a MrKim robotics 1X2, see wiki here: [www.reprap.org]:

Uses 1/4" OD x 0.170" vinyl tubing and 3/8" OD x 1/4" ID vinyl tubing. Soften 3/8" tube end in hot water and screw on to M8 leadscrew, and cut spare to the length of the motor shaft. Soften 1/4" tube, push over motor shaft and cut to length. Then push the 3/8" tube that is attached to your leadscrew over the 1/4" tube on the motor. They should grip each other well, and allow some flexibility. However, they are probably not strong enough to hang the X axis from like the Prusa; I have only used this method with the motors at the bottom of the frame on the Z axis.

droftarts Wrote:
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>However, they are probably not strong
> enough to hang the X axis from like the Prusa; I
> have only used this method with the motors at the
> bottom of the frame on the Z axis.

A couple worm clamps (hose clamps) will take care of that issue.

Edited 1 time(s). Last edit at 10/19/2011 05:58PM by NewPerfection.

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Tubes and hose clamps might be OK to get started. After that try to design and print one.

I'm surprised that in this whole thread you haven't posted the diameter of your motor's shaft, or which size of NEMA-XX motor it is. I'll assume that the shaft is 5 mm in diameter.

If that's the case, I'd suggest using an M6 leadscrew instead of an M8 leadscrew, and then you can use a coupling nut such as McMaster-Carr 93355A100. You might have to drill out the inner diameter of some of the threads to 5 mm, and add some epoxy to the threads, or else drill a small hole through the nut and the motor shaft and use a spring pin.

It would be a very un-flexible coupling, though.

Edited 1 time(s). Last edit at 11/19/2011 02:05PM by jbayless.