Threaded Z-axis rod not fixed to it's motor properly?

Hi everyone!

I posted this previously in a different thread, being slightly off-topic I guess it got lost there so here goes again.

One of my threaded z-axis rods seems to not be fixed to it's motor properly. If I gently pull the threaded z-axis rod up or push it down it moves about 1-2mm up and down. The other one is fixed and does not move at all if I try to pull or push. See this video clip for details: https://www.dropbox.com/s/s8iog3i1grbc9jp/20131012_205330.mp4

Is it supposed to be like that or is it a potential problem?
If so, any suggestions for how to fix it?

Regards, Daniel

 

Mine's like that too, and I'm not really sure the purpose of it being like that, but it's not problematic for printing so I'm supposing it's by design, and not something you need to fix or worry about.

 

That's great to hear. Thanks!
I guess that it leans toward a feature rather than a bug but it would be nice to get an official answer as well.

 

Is it actually moving up and down or is the coupling compressing? Maybe some couplings are defective and are softer then others?

 

@tesseract I'll check those screws in the coupling.
@seshan it seems to me, watching the clip again that the coupling is compressing when I push it down and it's extracting when I pull. About a mm in either direction.

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detach the coupling from the z rod, make sure the threaded z rod is all the way down in the coupling then retighten the coupler set screw. Those couplings are designed to flex to compensate for misalignment. But sometimes whoever installs them doesn't push them all the way down before setting the set screw you will get that motion.

another cause could be that the z rod itself is out of tolerance and not allowing the z rod to sit all the way down. Then you would have a space at the end of the z rod and the top shaft of the stepper motor which would allow that up and down motion.

 

Thanks for the help Cambo3D. It's really appreciated, however I don't quite understand.

How can I unscrew the coupling from the z rod and then make sure the z-rod is all the way in the coupling???

Did you really mean "unscrew the top coupler set screw, make sure ..."?

Regards, Daniel

 

sorry fixed. I meant to say detach the the threaded z rod from the coupler