Left z-axis motor seized up  

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mdaneman
(@mdaneman)
Estimable Member

Hi guys.  This morning I tried to start a print and my left z-axis motor was not moving (the right was still trying to).  The printer was printing fine just last night and has been printing fine for over a month.  If I turn off the power I can turn both motors and I don't see any particular resistance on the left one.  It the power is on the left motor is hard to turn (i.e. it's getting power).  The only recent addition I did was to connect an LED light to the 24v input of the Einsy board, but I have  printed a few things since then without a problem, so it's unlikely to be that.  I tried searching the forums for similar problems, and found some that mostly related to issues at first assembly (which this is not) and the issue was the hexagonal nut holding the X carriage to the Z or the Z-motor cover being too tight (see links below).  However, since I've been running problem free for a while, I'm not why these issue would suddenly occur. 

Would appreciate any advice.  Thanks.

https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/left-z-axis-motor-problems/#post-81974

https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-others-archive/non-functional-left-z-motor/#post-67783

Posted : 07/10/2019 7:07 pm
Tim
(@tim-m30)
Illustrious Member

First step is to put the printer back to factory - remove the LED lamps and test ... 

The motor jam nuts can tighten over time, and it's easy to rotate them up away from the motors as a test. 

Another friction issue is the upper supports aren't fitting right and one is holding the lead screw too tight.  Same for one of the T-nuts being damaged.  But manually stepping the lead screws with power off should catch something being tight.

Other causes are the cables not being plugged in fully: you can swap the two Z cables as a test of connector issues.

And it isn't out of the realm of possibility the motor controllers on the EINSY are flaking out.  Others have had to contact Prusa for a replacement.  Use the CHAT button on their store site.  Have them help you diagnose the issue.

 

It is always wise to get more than one opinion......
Posted : 08/10/2019 12:27 am
mdaneman
(@mdaneman)
Estimable Member

Thanks for the advice.  I disconnected and removed the LED light and, as expected, it didn't make a difference. Upon further fiddling, the left motor just doesn't seem to turn on its own (even though it is definitely getting power since it's hard to turn).  After running z-axis up and down a bit I see that the right motor gets warm but the left (bad) motor stays cold.  I have a strong suspicion that the motor went bad.  Will try contacting Prusa support. 

Posted : 08/10/2019 5:54 am
Robert-mm200
(@robert-rmm200)
Noble Member

Try swapping the Z Axis cables for a test. You may have a bad Einsy driver, and this would show it.

Posted : 08/10/2019 7:06 am
Tim
(@tim-m30)
Illustrious Member

The driver is the same for both motors, but the connects can have issues, so swapping the cables at the einsy can help refine where the problem is.

It is always wise to get more than one opinion......
Posted : 08/10/2019 7:53 am
mdaneman
(@mdaneman)
Estimable Member

Ok, with some help from Prusa, we debugged the issue.  It's a bad cable on that motor.  If I wiggle the cable I can get it to move.  Prusa is sending me a replacement motor, but in the meantime, I wanted to see if there's a straightforward way to fix the motor cable (ideally without taking the motor out of the printer).  I'm guessing I could try to find the bad portion of the cable, cut it out, and then solder the pieces back together.  Anyone have experience doing this type of thing?

Posted : 09/10/2019 3:55 am
Robert-mm200
(@robert-rmm200)
Noble Member

You are lucky - so to speak. The Z Axis motors don't move, so flexing is not an issue.

Locate which wire is broken by flexing them. If it were me, I would replace the entire wire leaving an inch or two on each end to solder to.

It will be easy to solder to. You can get fancy with shrink wrap or electrical tape is fine. It would be nice to use the same color and gauge wire.

Posted : 09/10/2019 4:35 am
mdaneman
(@mdaneman)
Estimable Member

Sounds good.  I would prefer to replace the entire cable+connector in case it's the connector that's bad and to only have one solder connection.   Any idea where to get such a cable without a motor?  I found these: Stepper Motor cable, but I think the connector (black) is wrong.  I can get an entire stepper motor with wire and (I think correct) connector for ~$16 on Amazon and cut off the wire, but that seems like a waste.

This post was modified 12 months ago by mdaneman
Posted : 09/10/2019 4:02 pm
Robert-mm200
(@robert-rmm200)
Noble Member

Given that I have never heard of a broken wire not subject to flexing - and I have heard about a lot of bad connectors - by all means check the connector. Customer Support should be able to tell you the connector type. Hopefully connections inside the stepper are good.

Posted : 09/10/2019 4:29 pm
mdaneman
(@mdaneman)
Estimable Member

Thanks.  I just found this awesome site on github that I didn't know existed: MK3 Compatible Parts.  It lists all the parts compatible with Prusa MK3 printers.  Looks like the connector is Molex 0050579404

Posted : 09/10/2019 5:15 pm
chocki
(@chocki)
Prominent Member

You can always buy a 0.1" dupont crimp connector kit and make your own 4 way male / female connectors, also if you use the 4 way female connector it fits onto the einsy board tight enough to not need the retaining clip.

I've used a 2x2 configuration to make a join inside the sleeving where it is not visible, and used these on all the OMC motors I have fitted as these only come with short leads and I have also made connectors for the e3d PT100 amplifier board and the connection to the einsy board.

Well worth the small outlay, the crimper also works with jst connectors and a few others as well.

Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet....
Posted : 09/10/2019 5:57 pm
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