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Z-axis coupling broke again (prusa mendel)

Posted by smellyfis 
Z-axis coupling broke again (prusa mendel)
July 24, 2011 06:56PM
so i just started testing my mostly built prusa (still need the hot-end/money to get) by moving the bits around and both my z-axis couplings broke. One had broken in assembly so i epoxyed it back together (broke in a different spot).
So my point is, is there anyone in the USA/Canada regions able to print me off one of these with the modifications for SAE parts? I am willing to pay for the shipping and or the amount of ABS/PLA needed to print it.
Re: Z-axis coupling broke again (prusa mendel)
July 27, 2011 05:49PM
larmym@gmail.com sold me two coupling's after i broke one of my "Z" axis
he told me he charges 5 bucks per hour for printing came out to 2.50 plus shipping.
i told him he needed to charge a 5 buck min.Ha Ha.
i sent him the money with pay pal no problems.
and i am making my own from alloy in a while
but first thing after i get a good print setup i will print what ever better one's i find on thingvers
Like nopheads as your link shows

Edited 1 time(s). Last edit at 07/27/2011 06:00PM by spad007.
Re: Z-axis coupling broke again (prusa mendel)
July 27, 2011 06:31PM
Have you done anything to understand why it broke in the first place? I have a mendel that is all belt driven. Belts tend to give slightly so you don't break stuff and don't loose steps. I wonder if this simplified mendel has a design flaw in the Z axis? That said I would consider making the coupling out of a stronger material. Like wood or aluminum for example. You can also buy steel couplings from McMaster Carr.
Re: Z-axis coupling broke again (prusa mendel)
July 27, 2011 09:53PM
Those new couplings work well and are a great improvement over the old design


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Experimenting in 3D in New Zealand
Re: Z-axis coupling broke again (prusa mendel)
July 28, 2011 03:13PM
They broke because it was not the greatest of prints, the first time it broke was when i was putting the motor into the coupling the i put it in to far and when i was backing it out it tore off (no lateral torque from me just a straight rip) the second time i didn't have the steps_per_mm_z set correctly in the firmware and it was going to fast and broke the other one and the first one in a different place.
I re-epoxyed them and covered the whole coupling with epoxy. It seems to be holding okay, the epoxy lets it flex some, but i would rather have the little better parts.
Thanks spad I will email them once i am back near my prusa currently on bike tour so spotty connections with people.
From MYCNCUK is almost the same as my problem

"all was working fine untill just, out of the blue the Z axis will not move and i keep getting the error safe z turned off ignoring safe z move! ive not touched anything since last time i had a mess with it and it was working fine! it wont move when im in the motor tuning setup either".


Warp9 E189010
smoothstepper driver Ver 17efb, 37, 2.08.36.

the z motor does not lock - a new motor did not lock.
I reversed the pins no luck
I swapped the z x cables on the controller z did not jog but, x would jog on z or x. cross signal ?????
I put x on z of the controller and it jogs. [cable ok, controller ok.????]
Mach3 knows and shows the movement. SS diag shows the movement in mach3.
I checked out ohms on x to see what readings were on a useable cable then I checked z and it has continuity.
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