Servo shaft connections

[krissondors]

I'm working on my retrofit and I realized that I need a way to couple the new motor shaft to the ball screws of the machine. The new motors I am using have 35mm shafts and the existing ballscrews are 3/4". The original motors just used a thin steel sleeve (like 0.050" thick) and 2 aluminum rings with set screws in them, clamping down on the sleeve and shaft. Seems like a dinky connection to me but I guess it works.

So my real question is, can I machine an aluminum or steel solid coupler, or should I use a coupler that allows for some misalignment? If I need a flexible coupler, which type do you recommend?

I found this coupler on McMaster which should work out the box, but it's hard to swallow the fact that I might have to pay pay almost $900 for 3 couplers

https://www.mcmaster.com/2764K818

[cnckeith]

if you want a broken motor shaft use a solid coupler.

use a CNC coupler like this.

https://amzn.to/3k5x8Jj

[krissondors]

[media][/media]

if you want a broken motor shaft use a solid coupler.

use a CNC coupler like this.

https://amzn.to/3k5x8Jj

That definitely gets the point across! Haha

Okay sounds good. Those rubber, spider gear couplers are tight enough? I noticed that the other types are often listed as "zero backlash"

[tblough]

I'd suggest these from McMaster - https://www.mcmaster.com/9845T67-9845T603/ These are zero-backlash, and the ones Keith linked to don't go anywhere near 35mm. Downloading the CAD, it looks like you could easily bore one of the 2.25" OD ones out to 35mm (without a keyway). It might not handle the torque a 35mm shaft motor can put out, but then neither can the 3/4" ball screw so it should work. On a clean oil-free shaft, these split collars grip much better than a comparable set-screw version.

[ShawnM]

Another great option is Ruland jaw couplings, these are high quality, zero backlash and you can mix and match bore sizes for each half and choose the durometer of the spider to match what you need.

https://www.ruland.com/servo-couplings/ ... lings.html

[krissondors]

I'd suggest these from McMaster - https://www.mcmaster.com/9845T67-9845T603/ These are zero-backlash, and the ones Keith linked to don't go anywhere near 35mm. Downloading the CAD, it looks like you could easily bore one of the 2.25" OD ones out to 35mm (without a keyway). It might not handle the torque a 35mm shaft motor can put out, but then neither can the 3/4" ball screw so it should work. On a clean oil-free shaft, these split collars grip much better than a comparable set-screw version.

Another great option is Ruland jaw couplings, these are high quality, zero backlash and you can mix and match bore sizes for each half and choose the durometer of the spider to match what you need.

https://www.ruland.com/servo-couplings/ ... lings.html

Thanks for the recommendations! For some reason I thought the spider style coupler would have backlash or be too flimsy for a CNC machine but it seems like these are the type of couplers often used. Thanks again!