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Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Wed Jul 11, 2018 1:34 am
by zemlin
This is a bracket I designed that prevents the ball nuts from rotating, but does not restrict the lateral movement required on these printers. This should result in smoother walls on printed parts, especially when using some z-hop where I have seen the ball nuts rotate inconsistently.

I printed mine from eSun ABS Plus, but any material with reasonable thermal resistance should work. If you only print PLA and run with your machine open, PLA would probably be fine. Your dimensional accuracy needs to be pretty good as the part is designed with zero clearance for the ball nut flats.

These bolted on quick and easy. Simply remove the nuts from below the build platform, slide the bracket into place, and reinstall the nuts. I ran mine up until the nuts were snug, then backed off 1/2 turn. That seemed to work well.

You need two parts per printer.

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Wed Jul 11, 2018 2:02 pm
by JohnSays
I like these. I was just about to do JetGuy's solution using copper tubing in place of the flat he used, but your solution looks... em, more professional/pleasing. Thanks for the upload.

I imported the stl into Simplify3D and it came in correctly scaled and perfectly oriented. I always get the correct scale with AutoDesk Fusion360, but never the correct orientation. With other programs I don't even get the correct scale. Is there anything special you did to get it to show up so perfectly?

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Wed Jul 11, 2018 2:15 pm
by zemlin
Thanks.
I normally use PTC Creo for modeling and also like Creo for exporting STL files - I have access via the day job. I don't do anything tricky, but I model parts around the system datum planes. Maybe that makes a difference.

I saw the flat-bar solution after I had started on this design. I'm sure it's a perfectly workable solution, but I already had this one cooking so I kept going. The parts pop into the machine super easy and feel rock solid once they're in.

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Wed Jul 11, 2018 5:27 pm
by EldRick
If the flats are a press-fit on the ball-nuts, then why bolt them in place at all? Why not just open up the holes for the top of the holding bolts, and press the piece on to the ball-huts from the top?

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Wed Jul 11, 2018 6:49 pm
by zemlin
EldRick wrote:If the flats are a press-fit on the ball-nuts, then why bolt them in place at all? Why not just open up the holes for the top of the holding bolts, and press the piece on to the ball-huts from the top?

Zero clearance is not much of a press fit. It's a very light press and wouldn't expect it to hang there forever with creep, expansion, and all the other stuff that goes on with plastic parts.

Also the flats are only on the bottom flange below the platform.

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Thu Jul 12, 2018 7:08 pm
by EldRick
Also the flats are only on the bottom flange below the platform.

Ah.

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Thu Jul 12, 2018 9:03 pm
by JohnSays
I have printed your stabilizers zemlin and they came out perfectly printed in eSun ABS+ black (which I just happened to have on hand). I installed them and they fit perfectly. So thank you for that.

It then occurred to me that the same sort of stabilizer could be made that bolts to the aluminum bed and that can pivot on that bolt. It would not need the four original screws because of the pivoting attachment to the plate. The advantages would be that it could be only the thickness of the bottom of the ball nut's flats and so give a little more height back to the build area. Also, and maybe not an issue at all, it would not slide against the support rod.

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Fri Jul 13, 2018 2:25 am
by zemlin
I don't believe my design costs any build height, as it doesn't hang any lower than the screws in the ball nut. Also, this needs to be free to move slightly in both X and Y, so a simple pivot isn't the same, although there are certainly other ways to skin this cat.

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Fri Aug 10, 2018 7:54 am
by DrExcess
Wow thanks for these.

They printed really nicely and the fit is perfect.

20180809_220820.jpg


20180809_230842.jpg


20180809_230838.jpg

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Fri Aug 10, 2018 2:49 pm
by zemlin
DrExcess wrote:Wow thanks for these.

Glad they worked out well for you.

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Fri Aug 10, 2018 5:52 pm
by Snalios
What exactly do these extra support do?

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Sat Aug 11, 2018 2:05 am
by zemlin
The ball nuts are not bolted tight to the print bed. The bolts are loose to prevent any binding that might occur due to minor misalignment of the linear motion bearings, rods, and the ball screws. The combination of the loose bolts and play in the holes means that the ball nuts are free to rotate several degrees while the printer is running. This movement can be inconsistent and cause small errors in the Z axis that would result in variation in the layer height during a print.

These brackets prevent rotation of the ball nuts while maintaining all the lateral freedom that is designed in to the printer.

Re: Bracket/Fix for N2 Rotating Z-Axis Ball Nuts

Posted: Sun Aug 12, 2018 2:09 am
by Snalios
Awesome!