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Z Axis weird behaviour ==> Won't calibrate [with VIDEO]  

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marc.n4
(@marc-n4)
Active Member
Z Axis weird behaviour ==> Won't calibrate [with VIDEO]

Hi Everyone,

Just finished the assembly of the mk3 kit and it seems my Z-axis is somewhat defective.

While in the selftest, one of the motor will turn (the right one) but not the other.

I tried going directly into calibrate Z option and it will work a tad better but the two motors do not turn at the same time and the right always seem to be "leading" the way which sometimes end up in the axis binding altogether and the motor growling...

Also, when powered-up, the right motor always seem to be energized and is hard to turn while the left oppose no resistance.
When I power the printer down, both are easy and do not show any significant drag.

Below is a link with a video of the problem.

Sorry for the vertical filming!

Thanks for your help,

Marc

Posted : 29/05/2018 3:35 pm
RH_Dreambox
(@rh_dreambox)
Prominent Member
Re: Z Axis weird behaviour ==> Won't calibrate [with VIDEO]

Your Z-screw covers are too tight and must be loosened.
Or, your trapezoidal nuts are too hard screwed in the plastic so they are slightly screwed.
Check the assembly manual chapter 4, step 3 and 6.

Bear MK3 with Bondtech extruder

Posted : 29/05/2018 5:16 pm
marc.n4
(@marc-n4)
Active Member
Topic starter answered:
Re: Z Axis weird behaviour ==> Won't calibrate [with VIDEO]

Hi RHDreambox,

Doesn't seem to be any of it.

Before posting I tried the usual methods : screw caps are loosened, I also basically loosened all the Z-axis from the motor mounts to the top mounts via the trapezoidal nuts but nothing changed...

Both axis seem quite loose and smooth when the printer is not powered up.

Bet regards,

Marc

Posted : 29/05/2018 6:08 pm
ejberg
(@ejberg)
Estimable Member
Re: Z Axis weird behaviour ==> Won't calibrate [with VIDEO]


Also, when powered-up, the right motor always seem to be energized and is hard to turn while the left oppose no resistance.
When I power the printer down, both are easy and do not show any significant drag.

This suggests that it isn't a mechanical problem, but rather an electrical one.
See if you have pushed the plug from the left motor all the way in. Or even try swapping the two Z motor leads and see if the problem is still on the left, or moves to the right motor.

Posted : 30/05/2018 7:36 am
marc.n4
(@marc-n4)
Active Member
Topic starter answered:
Re: Z Axis weird behaviour ==> Won't calibrate [with VIDEO]

Hi ejberg,

Indeed, good call. I switched the Z cables and the problem is now on the left side... 🙂

But now where do I go from here? Should I ask PRUSA to ship a control board in super express?

Marc

Posted : 30/05/2018 8:44 am
ejberg
(@ejberg)
Estimable Member
Re: Z Axis weird behaviour ==> Won't calibrate [with VIDEO]


Indeed, good call. I switched the Z cables and the problem is now on the left side... 🙂

Do you mean the problem remained on the left side (it was also left in your original post), or did you mistype and the problem moved to the right?

If it moved side when you swapped cables, then you have isolated the problem to the control board. As one of the motors is working, the Z axis driver ic is ok, so it probably is a bad solder joint or a bent pin in one of the plugs. The next step would be to contact Prusa.

If the problem remained on the left side, the problem is the left motor, its cable or plug.

Posted : 30/05/2018 11:56 am
marc.n4
(@marc-n4)
Active Member
Topic starter answered:
Re: Z Axis weird behaviour ==> Won't calibrate [with VIDEO]

Yes it was a typo,

The problem changed sides...
I'm contacting Prusa right away.

Posted : 30/05/2018 2:55 pm
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