Is flexible coupler helpful? I have been annoyed by z- wobble that happens on my Prusa Mendel. I plan to get two aluminium flexible coupler. Are they any good? I need some suggestion. I tried that z constraInts but they are not helpful. Thanks. https://reprap.org/forum/read.php?1,305126,305126#msg-305126 Fri, 12 Jun 2026 14:25:42 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,305126,320900#msg-320900 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,320900#msg-320900
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brnrd
So, the nut trap is large and allows the nut to wander? So, this trades some lag in the z nuts to eliminate wobble? I think the Prusa2 x-ends may have been intentionally made to have oversized nut traps to do the same thing. That's how my Prusa2 works.

lag? No I don't think so. Up and down the clearance is null, side to side there is play however.]]> foshon General Thu, 06 Mar 2014 17:00:32 -0500 https://reprap.org/forum/read.php?1,305126,307396#msg-307396 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,307396#msg-307396 brnrd General Thu, 06 Feb 2014 23:47:07 -0500 https://reprap.org/forum/read.php?1,305126,307297#msg-307297 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,307297#msg-307297 Clicky. they allow the nut to wander horizontally while keeping verticle constraints. Great for taking out the last bit of wobble.]]> foshon General Thu, 06 Feb 2014 17:35:57 -0500 https://reprap.org/forum/read.php?1,305126,306329#msg-306329 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,306329#msg-306329
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cnc dick
The real root of the problem for all of these machines is that the Z is not strong enough the rods should be continually supported and they should be mounted to a stiff frame. The idea is whatever the screw does it should not push the Z back and forth in other words the linear axis should be stronger than the screw

I think going to M5 threaded rods instead of M8 rods would reduce z wobble a lot. This is what was done on the Prusa3. This is a simple upgrade describe in thingiverse.]]> brnrd General Tue, 04 Feb 2014 20:44:10 -0500 https://reprap.org/forum/read.php?1,305126,306321#msg-306321 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,306321#msg-306321
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stonedcoldskier
Check this out: [www.thingiverse.com]

For me, making the change to M6 lead screws solved all of my z-wobble and banding issues. The wobble itself, as CNC_Dick pointed out, is the result of the Z-axis not being as rigid as it should be and the thinner lead screws will flex, allowing the 8mm smooth rods to do their job. Additionally, the change to metric threaded rods with 1mm (M6) or 0.8mm (M5) pitch, along with correct layer heights, will remove any banding issues associated with Z moves which are less than one full step.

There are other posts that will explain things much better than I have, but the comments / discussion on Thingiverse illustrate things pretty well.
thank you somebody finally understands the real root of the problem if somebody is building a machine from scratch and uses stronger Z guides supported it would be nice to see. This is part of the frame and doesn't move I would suggest possibly 16mm supported all the way or real linear rail and bearings. The only extra weight would be the bearings the hard part would be lining everything up there would be no forgiveness because nothing is going to spring so would take somebody with some skill to assemble. Shafts would have to be perfectly parallel if somebody had something that was the right size and used as a gauge to make sure they were exactly parallel top to bottom could be done. jpan has put up a couple more posts and he says it's not happening in the in the right direction so I don't know what would be causing his problem]]> cnc dick General Tue, 04 Feb 2014 19:39:25 -0500 https://reprap.org/forum/read.php?1,305126,306317#msg-306317 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,306317#msg-306317 check this post to see my prints please..]]> jpan General Tue, 04 Feb 2014 19:31:01 -0500 https://reprap.org/forum/read.php?1,305126,306244#msg-306244 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,306244#msg-306244 www.thingiverse.com]

For me, making the change to M6 lead screws solved all of my z-wobble and banding issues. The wobble itself, as CNC_Dick pointed out, is the result of the Z-axis not being as rigid as it should be and the thinner lead screws will flex, allowing the 8mm smooth rods to do their job. Additionally, the change to metric threaded rods with 1mm (M6) or 0.8mm (M5) pitch, along with correct layer heights, will remove any banding issues associated with Z moves which are less than one full step.

There are other posts that will explain things much better than I have, but the comments / discussion on Thingiverse illustrate things pretty well.]]> stonedcoldskier General Tue, 04 Feb 2014 16:54:29 -0500 https://reprap.org/forum/read.php?1,305126,306101#msg-306101 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,306101#msg-306101 jpan General Tue, 04 Feb 2014 13:34:05 -0500 https://reprap.org/forum/read.php?1,305126,305721#msg-305721 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,305721#msg-305721
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Dirty Steve
...The aluminum couplers are usually 5mm motor shaft to 8mm threaded rod. ....

There are several different configurations of these aluminum couplers to be had - make sure you get the right one for your setup. The stepper shafts are usually 5mm. I originally had 8mm threaded rod on my printer, and had corresponding 5mm-8mm couplers. Later when I went to an imperial lead screw (1/4 inch) I swapped my coupler for a 1/4 inch-5mm. So there are other configurations - if you go this route, just make sure you pay attention.

Most people here do not feel these are beneficial. Certainly, they're not ideal if your motors are above your shafts - too much weight on the spirals. I still have them on my printer, but I think I got better results from 1) removing any Z axis constraints - especially those on top, and 2) decoupling my X ends from the shafts. The nuts are not embedded in the X ends anymore - they are embedded in a separate smaller piece beneath the x ends. I have attached an openscad file that you can customize if you want.]]> jbernardis General Mon, 03 Feb 2014 20:09:22 -0500 https://reprap.org/forum/read.php?1,305126,305718#msg-305718 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,305718#msg-305718 jzatopa General Mon, 03 Feb 2014 20:03:57 -0500 https://reprap.org/forum/read.php?1,305126,305710#msg-305710 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,305710#msg-305710 Also, should I tighten the bearing on the linear rod even more? Sounds like that's what I should do...]]> jpan General Mon, 03 Feb 2014 19:22:51 -0500 https://reprap.org/forum/read.php?1,305126,305500#msg-305500 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,305500#msg-305500 cnc dick General Mon, 03 Feb 2014 13:42:26 -0500 https://reprap.org/forum/read.php?1,305126,305480#msg-305480 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,305480#msg-305480 Ohmarinus General Mon, 03 Feb 2014 13:19:10 -0500 https://reprap.org/forum/read.php?1,305126,305134#msg-305134 Re: Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,305134#msg-305134 Dirty Steve General Sun, 02 Feb 2014 21:44:41 -0500 https://reprap.org/forum/read.php?1,305126,305126#msg-305126 Is flexible coupler helpful? https://reprap.org/forum/read.php?1,305126,305126#msg-305126
Thanks.]]> jpan General Sun, 02 Feb 2014 20:38:10 -0500