Rotating Ball-Screw nuts

Topics around mechanical design, controller and electronics. Mods & hacks welcome.
zemlin
Posts: 294
Joined: Sat Oct 21, 2017 2:02 pm

Rotating Ball-Screw nuts

Postby zemlin » Tue May 15, 2018 4:23 pm

On one of the 3 Raise printers I use I watched the ball nut on the Z-axis rotate a few degrees during z-hop moves. This could cause some inconsistency in the layer thickness.

I understand that the screws are loose to prevent binding. Thinking about adding some spring washers or o-rings in the nut/bolt/flange interface to create a light clamping force but still allow lateral movement. Either that or make a collar that clamps on the top of the ball nut with an anti-rotation rod, perhaps running to one of the smooth Z-shafts so the nut cannot rotate but is not otherwise restricted.

Vice Chief
Posts: 63
Joined: Wed Aug 23, 2017 5:04 am
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Re: Rotating Ball-Screw nuts

Postby Vice Chief » Tue May 15, 2018 6:04 pm

It seems like it would also be possible to design a printed flex-joint that allows translation but not rotation. This is super-crude, but something like this (with one additional degree of freedom):

https://www.youtube.com/watch?v=H2gJuuhCV7w

Vice Chief
Posts: 63
Joined: Wed Aug 23, 2017 5:04 am
Contact:

Re: Rotating Ball-Screw nuts

Postby Vice Chief » Tue May 15, 2018 6:12 pm

Here's an XY flexure. Might try building something like this m'self.
https://www.thingiverse.com/thing:1072440

zemlin
Posts: 294
Joined: Sat Oct 21, 2017 2:02 pm

Re: Rotating Ball-Screw nuts

Postby zemlin » Thu May 17, 2018 2:23 pm

Something like that would be nifty, but I don't see a straightforward way to add that to the machine without impacting the Z-height and needing to drill additional holes in the platform. I envision a simple arm that surrounds the bottom of the ball nut, mates with the flats, and is held in place with the existing screws.


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