'calibration failed. check the axes and run again'  

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hanjo.v
(@hanjo-v)
Active Member

Hi!

After many great hours printing on my MK2s I upgraded it to MK2.5s (to build it to multi-material at some point in the future). Assembly went good - no issues there, but I run into a problem during the calibration wizard.

During the wizard program, when asked to move the z axis all the way up to the stops, it continues the wizard program by going down.

Just before it hits the bed (not touching) however it says:

'calibration failed. check the axes and run again'

The Pinda probe is functioning fine, it apparently spots the bed (it stops just before hitting) and also tested it with a piece of metal.

I am getting kind of desperate, don't know what to do now!

Thanks for helping me out! 

...
Posted : 22/08/2019 8:17 pm
fredrik.o2
(@fredrik-o2)
New Member

Hi!

I get the same error, and I have checked the axes to many times now it's not fun anymore...

When I do a auto home, the probe stops almost in the center of the ring, a little to the right.

But when I do the calibration, auto home stops in front of the ring to the left and then ask me to raise z to the top.

Is it the same for you?

I thought that it had something to do with the Bondtech extruder that I got, but reading here it seems that it is not the problem.

I can't find anything that works, and it is so annoying.

I should have skipped the mk2.5s upgrade, and just bought a new mk42 bed.

Posted : 12/10/2019 6:24 pm
rob.w5
(@rob-w5)
Trusted Member

Add me to this list.  I have many hours of successful printing on an MK2s, and upgraded it to an MK2.5s.  I can get points 1 and 2, but fail on point 3.  I am not sure if it would find point 4 or how it would do with the 9 point calibration.  I notice that the Y axis raises a bit when the printer goes to point 3 and does not seem to lower itself.  This may just be my imagination though.  I do see the red LED in the PINDA probe blink out as the sensor goes over the silkscreen circle in all three points I can get to.  There is also a chirping noise as the Z Axis motors make fine adjustments for all three points I can get to.  The Y axis does not move as easily as it did in it's MK2s form or the MK3s.  Perhaps I've made it too tight and the printer isn't getting the range of motion it expects?

The printer has Firmware v3.8.0-2684.

What IS a calibration point anyway?  I passed both poles of a magnet over them.  All I can guess is that they are weak magnets of opposite polarity to the fastening magnets.

I have a working MK3s + MMU2s, so I'm not in as bad shape as Fredrik and Hanjo, but it would be nice to get twice the work done via two functional printers.  While I await feedback from the community I will loosen the Y Belt just a bit and try calibration again.

Posted : 13/10/2019 11:14 pm
rob.w5
(@rob-w5)
Trusted Member

OK, a few more points of merit:

I meant X axis above when I wrote Y.  Loosening the belt so the extruder assembly moves easily from right to left did not improve the situation, but I do feel better about the life of the belt now.
I played around with other settings.  Z calibration finds the first three points just fine, but REALLY mashes down hard on the printbed on the fourth point, which is the one on the right side in the center.  Mesh Bed Leveling gets me to point 6.  Attempting a print failed on point 3 and requested an Axis check, which made it to point 7 one time 8 another, 7 the next, and all 9 after that.  After getting all 9 points on a "print" I tried the XYZ calibration again and got as far as  I'm lost, because I'm getting part way through and I know the alignment of the printer was good at least until the upgrade.

Just for kicks I tested the PINDA sensor by cutting a circle of aluminum tape about the size of the silkscreen circle and putting it under the PINDA sensor.  I was able to see the light go out when the tape got close, so I stuck the tape on the troublesome 3rd spot.  Same failure, aborts on that 3rd point.  Next, I disabled the stepper motors and moved the extruder assembly around the printbed, looking for the PINDA LED to go on and off.  It appears to need to be much closer to the printbed further back.  So I moved the PINDA down further one thread and ran the test again.  Same failure at that 3rd point, which now has aluminum tape on it.  My suspicion is that the heated printbed does not have enough metal mass on the calibration points to work well.  This is based on the number of complaints about this problem as well as a general internet search including YouTube regarding this problem.

  I'm not easily able to put a different bed in place, as I'd have to disassemble the MK3s, and I've given the printbed to the MK2s to a coworker in a different state.

Posted : 14/10/2019 12:24 am
hanjo.v
(@hanjo-v)
Active Member

Hello. I owe you an update.

Now, the printer is working again. I was under the wrong impression I did the 2S to 2.5S upgrade, but instead I was doing a 2.5 upgrade. So I followed the wrong instructions. Flashing it to firmware 2.5 resulted in a finished calibration sequence. 

But then I ran into the problem of a filament skipping/hopping extruder. This was because I used the shorter PTFE tube (from the 2.5S manual). I ordered a new tube locally, trimmed it like the picture, and the problem was gone.

Prusa ensured me that I am still able to upgrade to a mmu2s, although I have a 2.5 non-s now, using this upgrade kit:
https://shop.prusa3d.com/en/upgrades/183-original-prusa-i3-mk25smk3s-multi-material-2s-upgrade-kit-mmu2s.html

 This I still find confusing. Maybe someone can explain that to me? 

 

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Posted : 14/10/2019 12:09 pm
hanjo.v
(@hanjo-v)
Active Member

@rob-w5

Did you buy a 2.5 or a 2.5S upgrade kit. It sais on the cardboard box it arrived in.

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Posted : 14/10/2019 12:22 pm
hanjo.v
(@hanjo-v)
Active Member

@fredrik-o2

For you also the question, did you buy a 2.5 or a 2.5s kit? It sais so on the cardboard box. 

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Posted : 14/10/2019 12:25 pm
rob.w5
(@rob-w5)
Trusted Member

@hanjo-v

I bought a 2.5s upgrade kit.  It had a white sticker on the box stating so, and the printer now has a spring steel sheet and the extruder assembly has an angled fan and a ball/magnet as part of the filament sensor.  Why do you ask?

Posted : 14/10/2019 1:43 pm
hanjo.v
(@hanjo-v)
Active Member

@rob-w5

Because I did not 🙂 as you can read in my message above.

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Posted : 14/10/2019 1:46 pm
rob.w5
(@rob-w5)
Trusted Member

I may be able to shed some light on the differences you will see between a printer that can and cannot accept an MMU.  Your printer accepts filament that becomes 'controlled' when it enters the top of your extruder assembly.  An extruder that can work with the MMU2 has extra hardware that accepts a PTFE tube that runs from the MMU to the extruder.  In the case of my MK3 MMU2 being upgraded to an MK3s MMU2s, the filament sensor system changes from a magnet acting as a spring for the lever to block the optic sensor to a lever system that sits quite a bit higher than what is currently the top of the Extruder assembly.  You have the same PINDA sensor and plate, so I would assume the XYZ calibration process would be the same EXCEPT that the MK2.5 is a taller extruder assembly than the 2.5s.  so I would guess that the Z location needs to be a bit further down with the 's' models due to the shorter assembly.  If I were to have written the calibration routine, I would put effort into preventing the nozzle from crushing the heatbed, so I am starting to see a course of action to take.  But it will have to wait a few days, as I have some business travel in a few hours.

Posted : 14/10/2019 1:56 pm
rob.w5
(@rob-w5)
Trusted Member

OK, I'm back from overseas travel.

Since there is dialog about the possibility of having the wrong firmware in the MK2.5s, as in, having firmware for the MK2.5 instead being the cause of failure, I just reflashed my unit with prusa3d_fw_MK25S_3_8_0_2684RAMBo_13a_en_de.hex and got the same error: Fail to see the 3rd of 4 calibration points.  I can SEE the red light go out on the sensor when it passes the circle on the print bed, and I can feel the Z axis motors jiggle as the sensor passes over that mark.  With the stepper motors turned off, I can pass the extruder over those points and see the light turn off.  I have yet to use the menu options to see the sensor data change, but only have time to examine this in little bursts of spare time.  Exact same problem I had with most likely, the same firmware prior to reflashing it.
I've tried putting aluminium tape on the problem points.  I think I may just do a mesh bed leveling and go forward with the printer having never gone through the calibration wizard.

Posted : 18/10/2019 3:46 pm
rob.w5
(@rob-w5)
Trusted Member

Another shot at fixing this:  If I go to Support and watch the value of the PINDA sensor (or whatever the top option is) I can see a bit of ZERO value around a small ONE value in the center of each silkscreen circle.  In my problematic 3rd point I can't find any ZERO.  Everywhere around that third point is a ONE.  Maybe it's time to contact Prusa?

Posted : 18/10/2019 11:17 pm
jerry.s3 liked
rob.w5
(@rob-w5)
Trusted Member

I found my problem:  Although the printer worked flawlessly when it was an MK2s, it had too much skew to pass the setup wizard.  Adjusting the nuts holding the frame in position on the threaded rod did the trick.

Posted : 19/10/2019 3:20 pm
hanjo.v
(@hanjo-v)
Active Member

That is great news Rob! Hope we will have no problems anymore for a very long time...

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Posted : 19/10/2019 7:13 pm
rolf.h2
(@rolf-h2)
New Member

I'm encountering the same problem with the calibration.

Running the calibration XYZ fails with the error message: "Calibration failed! Check the axes and try again."

The calibration first works normally with me moving the Z-axis all the way up with the knob, asking the questions about metal sheet, cleaning the nozzle and paper. Then it moves the extruder all the way down. When the nozzle is slightly above the printbed (without metal sheet, of course), the printer stops and displays the error message at the very moment when the red light on the pinda probe vanishes. The printhead does not start to move laterally. The red light on the pinda probe is on when the printehead is far up.

After the error message, the Z-position is at 5.0mm.

I'm running firmware 3.8.1.

Selftest says everything is ok.

Up to now, I tried the following:

- lubricating all axes

- checking that all axes move well

What can/should I do now?

Any help is appreciated.

 

Best regards

Rolf

This post was modified 7 months ago by rolf.h2
Posted : 21/03/2020 3:20 pm
rolf.h2
(@rolf-h2)
New Member

I found my mistake. It was a really, really stupid one: I had flashed the wrong firmware, i.e. a MK 2.5S firmware on an MK 2.5 printer.

 

Here is the full story: As I was starting the conversion with an MK2S it seemed very clear to me that the result would be an MK2.5S. However, this is not the case. I suddenly saw on the paper accompanying the kit "MK2.5", while the display on the printer showed "MK2.5S". This seemed strange to me, and then I found out that there is a special firmware for MK2.5 (you have to scroll down quite a bit on the firmware page).

After flashing this correct firmware, the XYZ calibration ran without problems.

 

Sorry for taking anyones time thinking about my problem - I will try harder next time before asking here.

 

Best regards

Rolf

This post was modified 7 months ago by rolf.h2
Posted : 21/03/2020 8:47 pm
john.g24
(@john-g24)
Active Member

So, it looks like I've joined the list of folks with the Z axis calibration failure.   My MK2 had been working just fine since day 1 but the bed was now getting chewed up so I figured time for the upgrade to get benefit of the steel sheet.   The upgrade build went fine and,like the other folks, self test passes OK.   After I raise the extruder to the top and then hit ok after I confirm no sheet is fitted, the extruder goes to the bed, stops just before it hits and I get the 'calibration failed, check axis and run again' error.   I'm running FW 3.9.0-3421 and its the 2.5S version.   Incidentally, when flashing the firmware the printer lights up all the pixels and the beeper sounds continuously until the flash completes successfully.   I don't know if this is normal.

I've checked and cleaned all the rails and screws, I've checked the frame geometry.   Everything seems to be aligned and square.   I'm all out of ideas at this stage and I'm disappointed to see so many folks have similar issues with this upgrade.   Had I checked first I would have left the kit in the box!   Anyway, if any of you have some other suggestions I could try I'd be very grateful.

Thanks,

John 

Posted : 02/06/2020 10:38 am
john.g24
(@john-g24)
Active Member

After much reflection I found the problem in my case.   The nozzle was too low in relation to the extruder body.   What tipped me off was the fact that the Pinda probe was almost all the way down in its clamp.   Upon dismantling the extruder I found that the hot end heatsink had come unscrewed thus placing the nozzle about 4mm lower than it should have been.  I just screwed the heatsink back to where it should have been and re-assembled everything.   I don't know how this happened but at least I found a concrete answer and the calibration went fine after that.   This may help others if you're at your wits end to get it to pass the Z axis calibration.

 

 
This post was modified 5 months ago 5 times by john.g24
Posted : 06/06/2020 5:37 pm
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