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Replaced my stepper motor, now get an instant calibration failed error. Any suggestions?
 
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Replaced my stepper motor, now get an instant calibration failed error. Any suggestions?  

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david.m122
 david.m122
(@david-m122)
New Member
Replaced my stepper motor, now get an instant calibration failed error. Any suggestions?
I had a working MK3. It fell off a table and then sat unused for a while. I have been wokring on getting it functioning again. I had to replace the left stepper motor. I got a NM17 one on amazon. I wired it up color to color and it passed all the tests.
As soon as I get to the calibration though I get the "Calibration failed! check the axes and run again". It does even move up or down. One of the troubleshooting tests I read was to check the sensor, but that works with the light turning off right away.
One thing I did notice, was that when I press the dial down for three seconds and get to the page that lets me make the adjustments, it does make a difference in which way a rotate the dial, the head moves down. I thought maybe the other NM17 motor has to have its wires reversed, which I did, but it didnt help.
 
Any suggestions?
 
Thank you
Posted : 02/04/2020 12:25 am
JPLau001
 JPLau001
(@jplau001)
Eminent Member
RE: Replaced my stepper motor, now get an instant calibration failed error. Any suggestions?

A MK3's standard firmware is tuned to the stepper motors supplied with the original printer.

Obviously, both the left and right Z-axis stepper attached lead screws and trapezoid nuts must also be paired and physically identical or you'll have the x-axis tilting as it moves up and down on the z-axis because one side will move vertically at a faster rate per step. 

Check that the trapezoid nut on the left side z-axis is identical to that on the right and both are mounted in the correct top/bottom orientation as pictured in the MK3 assembly manual. Having the trapezoid nuts mounted upside down will also fail your calibration as the calibration routine also checks the detected z-axis length via the number of steps required on both steppers to move from top to the bottom of the z-axis.

Better still buy an official replacement from the MK3/MK3S spares in Prusa's store for about USD 32.86 (+postage, etc.). You'll have to logon to your "Prusa account" in the store to see and access the Spare Parts section.  The url for a replacement left Z-axis stepper is  https://shop.prusa3d.com/en/spare-parts/385-stepper-motor-z-axis-left.html

 

This post was modified 4 years ago by JPLau001
Posted : 02/04/2020 3:02 am
david.m122
 david.m122
(@david-m122)
New Member
Topic starter answered:
RE: Replaced my stepper motor, now get an instant calibration failed error. Any suggestions?

@jonathan-lin

I used the same trapezoid nut from the broken motor and mounted properly. I tried purchasing an official replacement but it's only letting me at to wish list even though it says in stock.

 

Thanks

Posted : 02/04/2020 5:55 am
JPLau001
 JPLau001
(@jplau001)
Eminent Member
RE: Replaced my stepper motor, now get an instant calibration failed error. Any suggestions?

@david-m122

You'll need to use the matched trapezoid nut that came with the new leadscrew stepper motor especially. The leadscrew and nut must have matching specifications. If the screw pitch, type, or other specification differs between the screw and the nut then you'll have issues.

For the Prusa I3 MK3s z-axis both leadscrew steppers must match.

As per ordering a replacement from PRUSA, it looks like the COVID-19 is affecting availability at this time. 

Posted : 04/04/2020 3:55 pm
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