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MGammal
(@mgammal)
Active Member
Z-axis rigid coupling

Has anybody tried to swap the tube coupling for the z-axis with a rigid coupling? If yes, have you seen any benefits? Does the added torsional rigidity actually improve the quality of the prints?

Napsal : 28/10/2015 7:44 am
gordon d..l
(@gordon-d-l)
Active Member
Re: Z-axis rigid coupling

The plastic tube was really not the answer. It printed for a short time and spun off.
Just installed rigid coupler and everything pints well. I will keep you posted.\

Napsal : 01/11/2015 8:08 pm
MGammal
(@mgammal)
Active Member
Topic starter answered:
Re: Z-axis rigid coupling

I'm not in favor of the tube as well, and I got feedback from some friends using other printers that using a rigid coupling improved the print quality.
I had the couplings machined, but I'm using 5mm long set screws that extend 1-1.5mm outside the coupling and they might hit the plastic part that carries the Z-axis end stop. Did you modify these parts? In my case I might need to grind them a bit.
One last question, did you use loctite on the set screws? is it necessary?

Napsal : 03/11/2015 10:05 am
Dartanelo
(@dartanelo)
Active Member
Re: Z-axis rigid coupling

I was surprised when I first saw the couplings too. That said they have been working fine for me. Still I am interested in what you did. Do you have any pictures of your new set up?

Napsal : 08/11/2015 4:18 am
MGammal
(@mgammal)
Active Member
Topic starter answered:
Re: Z-axis rigid coupling

I've attached a photo here.
As you can see the space is really tight, I had to grind the 2 plastic stoppers beside the threaded bars to make room for the couplings and the extending setscrews.

I'd recommend the following:
Coupling: outer diameter 12mm, height 40mm.
For the bores, motor shaft side: use a 5mm drill bit on the lathe, works fine.
Threaded bar side: drill with a 4.5mm drill bit then use a reamer to make it 4.8 or 4.9, as the M5 threaded bar is never 5mm in diameter.
Setscrews: I used M4x5mm, but they extend outside, I'd recommend using M4x4 or M4x3mm if you can find them.
For the threaded bar side, I made 2 setscrews 180 degrees apart, to help center the bar.

Hope this helps.

Napsal : 08/11/2015 7:08 am
petasto
(@petasto)
Trusted Member
Re: Z-axis rigid coupling

I was searching about rigid couplings quite a long time and can't recommend it. Connection between steppers and threaded rods is flexible for a purpose as the rods aren't perfectly straight. The plastic tubes transfer only the rotation and they do it just fine. If you make it rigid, these threaded rods start to push against smooth rods as they turn and result in higher bearings wear and maybe some Z-wobble issues.

Napsal : 08/11/2015 8:58 am
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