Self-centering tapered-thread Z-axis coupling (5/6/8mm)

by loco, published

Self-centering tapered-thread Z-axis coupling (5/6/8mm) by loco Jul 16, 2014


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NEW VERSION AVAILABLE: http://www.thingiverse.com/thing:602481

This is a rigid self centering axis coupler.
It's ideal for printers like Prusa i3, because the z-axis threaded rods normally have no dedicated bearings or bushings to ensure coaxiality between the steppers and the rod itself.
This Thing adds some rigidity to this system and keeps the axis coaxial to each other.
Make sure your rods are as straight as possible.
Bent rods can lead to Z-axis wobble. In this case you should install an anti wobble system.
14-07-16: Added a 5/8mm version
14-07-17: Added a 5/6mm version - use nut_5mm for both sides


Print this as fine as possible to get nice threads.
This one is printed with 0.16mm layer height, 2 perimeter, 100% infill.

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Thank you for excellent work! Just printed this in PETG and installed, seems to be working very well based on few test prints! I had some visible rod wobble with the standard flexible coupling, all gone now! Seems to fit tight now, I hope it will not loosen up and fall off (I have a top mounted Z motor).

Update: mine came loose and popped off the motor shaft the other day, when I was manually moving the nozzle up & down, so be careful with this if you have a top mounted Z motor. I went back to standard coupler + stabilizing "cage" around it.

Could you make the 8mm nut 0.750 or (1mm if easier), smaller on the outsides ? they hit my smooth roods I kind a solved the problem by sanding them down on the corners but it looks messy.

Just printed the 5 to 8mm out and installed; fits on nice and tight; threads very nicely. Haven't tested with a print yet but I am impressed by this coupler so far.

Comments deleted.

Disregard my request lol I ll use as is, only thing, I had to sand off the corners because im using a 17mm center for my z axis and they were lightly taping my smooth rods, other then that, FANTASIC ! Way better then those china made z couplers. Btw How the heck were you able to make the treads on the tapered parts? I been trying and trying with fusion and it wont let me make them.

Great Fix,This part reduced my z ribbing by a whole lot.

Am I right in thinking that this part should fit over the rod/motor freely until you do the nut up? Ive still got a little z ribbing going on and I think it may be the abs shrank after it cooled making it a tight fit.

Thanks again,

This is the most useful thing I have ever printed! It fixed my z wobble issues. Thx for sharing

Please make a 5mm->10mm version too (:

Hi there,
i'm redesigning this coupler at the moment. I'll make a 5/10mm version, too.
Come back in the next few days, or follow me to get notified when It's done.

Could you explain what self-centering means or how it works? I'm not sure I see the magic. I guess it's just about the 3 fingers clamping with equal force?

You're correct. When tightening the nuts, the 3 fingers will clamp the shafts inside them while aligning the shafts axis (at least in theory) perfectly centered (concentric or coaxial).
In some type of clamps the axes of the two shafts are not aligned, especially when one of the shafts has a slightly smaller diameter than the couplers bore.
This Thing should eliminate Z-wobble caused by misaligned axis. However, it is important to use straight shafts as there is nothing to compensate the movement of a bent shaft, which could lead to wobble again.

Thanks for the explanation, I will try this once I got straighter rods.