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[Solved] Y-axis self test failing consistently  

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Filip Sádovský
(@filip-sadovsky)
Member
Y-axis self test failing consistently

Hello, yesterday i did finish building MK4 kit. Everything went smooth on first try except Y axis self test. I already checked belt tension (using prusa web app tuner) placement of all components and over all any possible loose screws but everything seems to be fine. Any idea what could be wrong?

Posted : 25/07/2023 6:17 am
Filip Sádovský
(@filip-sadovsky)
Member
Topic starter answered:
RE: Y-axis self test failing consistently

Aaaaand as iam not exactly patient when it come with searching for solutions i did go through Y assembly again to make sure no error was made with fresh morning mind and for sure there was. Be super mega careful and make extra sure you follow especially this part on dual bearings side of Y assembly:


Unlike the previous bearing, position the bearing as close to the center....... Beware, the bearing must not touch the edge.....

Posted : 25/07/2023 7:09 am
Jmagi
(@jmagi)
Member
RE: Y-axis self test failing consistently

What is the “edge”?  Makes no sense to me… do you mean locate both pushed toward center but leave just a bit showing on outsides?   I keep having the y acix failure and am quite frustrated.

Posted : 26/08/2023 7:07 pm
MarioAnders
(@marioanders)
Member
RE: Y-axis self test failing consistently

Nabend, mir geht es genau so. Habe den Drucker auch gerade zusammen gebaut und wollte voller freude schauen ob es geht und bekomme auch die Meldung das die Y Axe nicht geht und bei der Z Achse ist ein Strich.

Dachte ich kaufe dieses mal einen guten Drucken nach dem ganzen China Dingger aber es geht schon scheisse los.

Posted : 30/08/2023 7:04 pm
Lvet
 Lvet
(@lvet)
Estimable Member
RE: Y-axis self test failing consistently

I just finished assembling the MK4 kit, and I have too problems with intermittent Y axis calibrations failures.
As far as I read so far, the most common problem lies in the position of the two bearings on the left rod.

If you look at step 30 in the chapter "7. Y-carriage & Heatbed assembly", you will see that the bearings need to be positioned as close to the center as possible. If the edge of the bearing is too far outside it will prevent the heatbed to fully move and will make the calibration fail

Posted : 31/08/2023 8:19 pm
Fignutz
(@fignutz)
Active Member
RE: Y-axis self test failing consistently

A month and 50 hours with support and this piece of shit still fails the y test every time. I regret this purchase 

Posted : 28/10/2023 12:31 am
MichalV
(@michalv)
Member
RE: Y-axis self test failing consistently

Same problem, same solution. The bearing was completely even with the the side of the pocket. I pushed it back 1-2mm so it looks exactly like on the picture and voilá, test passed. Step 19 in Y-carriage.

Posted : 03/11/2023 9:27 am
brescoli
(@brescoli)
Member
RE: Y-axis self test failing consistently

I had the same problem that the Y axis test was systematically failing, independently of the belt tension or the positioning of the bearings. I had trouble shoot the problem and the root cause was that I had installed wrongly the Y-Belt tensioners (step 29) of the Y-Axes assembly instructions. I had installed the one that goes left in the right position and the left one in the right position. I had re-installed the Y-belt tensioners in the right position and the problem of Y axis fail is solved. Now it always passes the test.

Posted : 03/12/2023 12:15 pm
vhubbard
(@vhubbard)
Estimable Member
RE: Y-axis self test failing consistently

As stated by brescoli, putting the belt holder in correctly is critical.  The Y axis belt holder is part of the bump stop.  The part with the non-adjustable bolt hole goes to the back, nearest to the Y axis servo mount.  If the bolt comes loose, Y homing has problems also.  If the Y motor mount and belt holder "bump" surfaces aren't smooth a little sanding to get the "bump" surfaces smooth also helps.  

Posted by: @brescoli

I had the same problem that the Y axis test was systematically failing, independently of the belt tension or the positioning of the bearings. I had trouble shoot the problem and the root cause was that I had installed wrongly the Y-Belt tensioners (step 29) of the Y-Axes assembly instructions. I had installed the one that goes left in the right position and the left one in the right position. I had re-installed the Y-belt tensioners in the right position and the problem of Y axis fail is solved. Now it always passes the test.

 

Posted : 10/12/2023 3:29 pm
b4de4nd
(@b4de4nd)
Active Member
RE: Y-axis self test failing consistently

did you build it yourself?

Posted : 11/12/2023 1:41 pm
GreenPekka
(@greenpekka)
Member
RE: Y-axis self test failing consistently

I have a self assembled mk4 and also ended up with the dreaded Y-axis self test fail. I tried everything from downgrading the firmware, ensuring that all was aligned, pieces in the correct place, bearing alignment and pulling my hair !! The last post with the belt tension saved the day (actually took a week). By loosening the tension it worked, so do not over tension as that can cause problems. Thanks for all the great posts in this thread, thanks vhubbard for the tip

Posted : 12/12/2023 12:24 pm
R777
 R777
(@r777)
Member
RE: Y-axis self test failing consistently

Congratulations!I bought a mk4-kit - 2 pcs. One failed the y-axis test (the screen showed 211mm, which seems too much). It turned out to be a problem in the location of the bearings on the left. Although I did as in the photo in the instructions - the bearings are as close as possible to the center, but so that they do not touch the edge of the platform - that is, everything was the same on 2 printers. I moved one bearing (which is closer to the front side) by 1 mm from the center, that is, closer to the screen - this was enough to reduce the movement of the platform and the test was passed. Good luck!

Posted : 16/12/2023 9:34 am
Kortsy
(@kortsy)
Member
RE: Y-axis self test failing consistently

This is what appears to have helped me. Great find!!

Posted by: @r777

Congratulations!I bought a mk4-kit - 2 pcs. One failed the y-axis test (the screen showed 211mm, which seems too much). It turned out to be a problem in the location of the bearings on the left. Although I did as in the photo in the instructions - the bearings are as close as possible to the center, but so that they do not touch the edge of the platform - that is, everything was the same on 2 printers. I moved one bearing (which is closer to the front side) by 1 mm from the center, that is, closer to the screen - this was enough to reduce the movement of the platform and the test was passed. Good luck!

 

Posted : 19/12/2023 11:21 pm
halfdink
(@halfdink)
Member
RE: Y-axis self test failing consistently

I can only repeat: great finding! The official troubleshooting guide does not even mention the positioning of the left linear bearing, but that exactly was the problem. Thanks a lot!

Posted : 27/12/2023 6:04 pm
Gamerrangerbob
(@gamerrangerbob)
New Member
RE: Y-axis self test failing consistently

Thank you so much, same issue, 211 was the reading and failing. Moved the left front bearing and passed!

Posted : 28/12/2023 10:04 pm
miroslav.h4
(@miroslav-h4)
Honorable Member
RE: Y-axis self test failing consistently

The error is in the FW. Older versions of the test when measuring the length of movement of the Y-axis apparently only had limitations from below, i.e. the Y-axis had to travel at least 211 mm before hitting the front bracket. If she had driven more, nothing would have happened. In newer versions, some developer probably dug into the things that worked, and added a restriction from above, so if the Y axis moves a little more than 211mm + some small tolerance, it will declare an error. The solution to the problem is on the side of Pruša: either increase the tolerance or throw out this senseless restriction altogether. And why is it exactly 211 mm? Because the Y-axis program stroke is 210mm, but the actual mechanical stroke is 215mm. the Y-axis still has 4 mm of clearance to the rear stop so that it can be moved when searching for the rear position, and the actual "zero" position of the Y-axis is 4 mm from the rear stop and the front reachable position of the Y-axis is 210 mm, i.e. 1 mm from the front stop . And solving the front stop by impacting the bearing into some part is mechanical nonsense. At the same time, it would be enough to make a threaded hole in the Y carriage at the front next to the left bearing and attach a component with an adjusting screw here, with which I can adjust the front stop regardless of the position of the bearings.

Posted : 29/12/2023 8:42 am
miroslav.h4
(@miroslav-h4)
Honorable Member
RE: Y-axis self test failing consistently

Small correction, the adjustment part does not fit next to the bearing, because it does not go through the frame, which was a bad idea. However, it fits in the middle just next to the belt tensioner and the adjusting screw could rest against the front pulley body.

Posted : 29/12/2023 8:56 am
Fignutz
(@fignutz)
Active Member
RE: Y-axis self test failing consistently

Thank you so much. I was going to completely rebuild the y axis again but i figured there would probably eventually be some firmware fix. Im just glad i can at least use my other printers. It has to suck if you were upgrading your only frame to mk4 and get this disappointment. 

Posted : 29/12/2023 4:49 pm
HoryAycardo
(@horyaycardo)
Eminent Member
RE: Y-axis self test failing consistently

During the XY Axis test, X passes.  On the Y test, the bed goes to the rear, bumps it twice and then races to the front to show a Y:211 and of course, a failed Y axis test. Am calling it a night and am going to try to solve this tomorrow. I hope Prusa increases the tolerance as Miroslav posted.

Posted : 30/12/2023 2:30 pm
HoryAycardo
(@horyaycardo)
Eminent Member
RE: Y-axis self test failing consistently

Several folks have reported issues with FW 5.1.2.  Downgraded the firmware to 5.0.0 and my printer passed the self test!  

Posted : 30/12/2023 3:40 pm
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