Z-axis calibration failing after leveling  

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sheva.serg
(@sheva-serg)
New Member

Hi, trying to calibrate new MK3S built from the kit, firmware version 3.8.1-2869. Stuck on Z-axis calibration step.

After X-axis assembly is brought up and leveled the calibration software prompts to clean the nozzle, remove the metal print sheet and put a sheet of paper on the bed. When I hit 'OK' X-axis assembly starts to move down and almost immediately, maybe 2 or 3 mm from the top point it stops and the error message is displayed:

"Calibration failed! Check the axes and try again."

There is not much of a wiggle room in Z axis to be honest but I've tried to reattach, tighten/un-tighten top Z axis caps, switching left and right Z axis smooth rods and lubricating them.

inb4

* Self tests including Z axis finish with no issues.
* I'm able to move X axis assembly up and down turning screw rods using no excessive force - I'd rather say I subjectively feel less resistance turning screw rods than moving the printing head along X axis.
* I have tried to unscrew trapezoid nuts to make sure they don't lock up motors.

If anyone can suggest what I can do or how to learn what exactly is wrong with my build I'd really appreciate that. Thanks!

Posted : 16/12/2019 1:31 am
Robert-mm200
(@robert-rmm200)
Noble Member

Remove the bracket screws from the trapezoidal nuts and verify they turn freely on the threaded rod. They should be really smooth.

The problem you describe can be caused by one or both trapezoidal nuts being cross threaded during assembly.

After that, loosen the stepper motor screws and the upper bracket screws and run the Z axis full length a couple of times.

Then tighten all the screws. What you are doing is making sure all the rods are parallel.

Posted : 16/12/2019 5:07 am
sheva.serg
(@sheva-serg)
New Member

Checked trapezoidal nuts, they turn butter smooth.

Tried to loosen stepper motor screws/upper bracket, ran Z axis up and down several time to force rods into a proper position, same problem.

Tried to run tests with loose screws in motors and upper bracket thinking maybe rods would align if shaken, same problem.

I wonder is there a way to get a better insight why the test fail.

Posted : 16/12/2019 7:32 am
Robert-mm200
(@robert-rmm200)
Noble Member

It fails because increased friction make the code think it has reached an endstop...

Last arrow in my quiver is raise the dust covers on the steppers a bit, so they are not touching the steppers.

Next stop would be contact Support. EShop above, sign in, then use the Chat button.

They are really very good and can step you through it. Tell them the steps you have done.

Posted : 16/12/2019 9:12 pm
sheva.serg
(@sheva-serg)
New Member

Robert, it looks I found the problem, same as here - basically if P.I.N.D.A. sensor is toast Z axis calibration will bail out. Thanks for your time!

Posted : 17/12/2019 2:49 am
Robert-mm200
(@robert-rmm200)
Noble Member

Good job finding it! I will add that to my checklist.

Posted : 17/12/2019 5:26 am
patrick.fekete1992
(@patrick-fekete1992)
New Member

I am also having the problem with the XYZ-calibration failing, with the error message

Calibration failed! Check the axes and try again.

Is there some kind of step-by-step guide I can run through to solve this problem?

Posted : 03/01/2020 1:37 am
i.am.goga
(@i-am-goga)
New Member

@patrick-fekete1992

I struggled with the same issue too. 

In my case, the double spool holder was attached at the front which caused the inaccurate adjusted Z-Axis height.

I have attached the picture with the correct position of the double spool holder - it should be at the back:

Also, make sure that P.I.N.D.A. is sitting at the right height; the instructions to use the zip tie did not work for me ... I had to manually adjust the height of P.I.N.D.A.  by running Z-Axis calibration: lowing the P.I.N.D.A. sensor when the nozzle toches a paper; and rising it when the calibration fails. 

 

This post was modified 9 months ago by i.am.goga
Posted : 03/01/2020 10:40 pm
patrick.fekete1992
(@patrick-fekete1992)
New Member

@i-am-goga

It was the trapezoidal nuts on both sides, a buddy of mine suggested raising them a couple of milimeters and it solved the issue.

Make sure to run the initial self test again though, because raising them a bit too high will cause an error.

Posted : 04/01/2020 10:57 am
Robert-mm200
(@robert-rmm200)
Noble Member
Posted by: @patrick-fekete1992

@i-am-goga

It was the trapezoidal nuts on both sides, a buddy of mine suggested raising them a couple of milimeters and it solved the issue.

Make sure to run the initial self test again though, because raising them a bit too high will cause an error.

I am trying to understand this one. You put spacers under the trapezoidal nut screws?

That would have the effect of moving the Z contact point up (Z end stop)?

You have verified assembly of the parts was correct? (Nothing upside down)

 

Posted : 05/01/2020 5:09 pm
patrick.fekete1992
(@patrick-fekete1992)
New Member

@robert-rmm200

No no no. I just loosened them a bit. I mean to me it didn't seem like anything was out of the ordinary (upside down, or anything like that)

Posted : 05/01/2020 11:05 pm
Robert-mm200
(@robert-rmm200)
Noble Member
Posted by: @patrick-fekete1992

@robert-rmm200

No no no. I just loosened them a bit. I mean to me it didn't seem like anything was out of the ordinary (upside down, or anything like that)

Loosening them a bit may have allowed them to align better.

If your vertical rods are really not parallel, it is helpful to loosen the brackets at the top, and the stepper mounting screws.

Run the Z axis up and down a couple of times to let everything align.

Then tighten it all up. Including the trapezoidal mounting screws...

This is all something to keep in mind if your Z problems return.

Posted : 06/01/2020 2:03 am
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