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X-Axis Weirdness  

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earhornjones
(@earhornjones)
New Member
X-Axis Weirdness

I've had my mini since June of 2020, and have been printing without any problems until recently.

I was getting some layer shifting in the X-axis, so I checked the grub screws, and found them to be tight, and installed correctly.

When I do a mesh bed level, the printer moves to the front right of the bed, probes for the first point, then, when moving to the next point, sometimes moves only a tiny bit.  This is repeated for all points, sometimes moving the "regular" distance, and sometimes moving only a few millimeters.  Sometimes this results in the mesh bed levelling occurring across only a tiny portion of the bed.  Sometimes it fails, because the combination of steps leaves the probe hanging out beyond the right edge of the print bed.

Here's a video of what I'm seeing.

Any ideas on what's going on here?

Posted : 19/07/2021 2:39 pm
triti
(@triti)
New Member
Same thing happens to me occasionally

I don't have any issues with layer shifting on my Mini+ but I do occasionally have something very similar happen during a mesh bed level. The X/Y/Z axes all auto-home, the print head moves to the first probe point at the front right corner of the bed, the X axis will then move to the left by about a millimeter or so, probe, move a millimeter, probe, repeat similar to your video. Only difference I get is when the Y axis moves to start probing on the next row, when the print head moves to the right, it'll slam against the limit and keep probing, slamming, probing, etc. until the Y axis moves to start probing the third row. At that point, it starts probing normally for the third and fourth row.

But the printer only does it sometimes and I haven't yet figured out how to consistently recreate the problem. The X axis belts are at the correct tension (measured with the tension meter printed from this site), all the screws are tight. If I see/hear it happen at the start of a print job, I'll cancel and restart the print and so far the mesh bed level always succeeds on the second try and the prints all come out looking great. It feels like a software/firmware problem.

Posted : 23/07/2021 1:52 pm
triti
(@triti)
New Member
Mesh bed leveling weirdness

Here's another forum post with someone else replicating what looks like a very similar problem: https://forum.prusaprinters.org/forum/hardware-firmware-and-software-help/bed-level-not-scanning-whole-bed-on-first-print-only/

Posted : 23/07/2021 10:09 pm
earhornjones
(@earhornjones)
New Member
Topic starter answered:
Mesh bed leveling weirdness

I'm closing the loop on this one.

I worked with Prusa tech support, and they recommended the following:

1. Tightening the grub screws on the X-axis gear. - This was also my first thought, so I performed a tear-down of the axis, and verified that the gear was properly aligned, and that a grub screw was secure against the flat surface on the motor axle, and that both screws were tight.

This did not solve the problem.

2. Replacing the X-Axis bearings. - While the X-axis felt tight when I moved it by hand, if I removed the print head assembly, the carriage moved as smoothly as I've ever seen.  This seemed to contraindicate a bearing issue.  I replaced them anyway.

This did not solve the problem.

3. Replace the MINDA probe with a Super-PINDA.  - I'm not sure what this was supposed to do, and my MINDA passed every test I could think of.  I did it anyway.  Initially, the printer still failed X-Axis self checks, but the mesh bed levelling seemed to work normally.  

After the install of the Super-PINDA, I readjusted some of the cable management that was a little disarrayed from the install.

After that, all self tests passed, and printing is working normally.

If I had this to do again, knowing what I know now, I think I'd cut the zip ties holding the X-Axis cables in place, remove the fabric sleeve, carefully repack everything in the sleeve, and replace the zip ties with less snug ones.

In the end, the actual solution is unclear, but my Mini is working.  Hopefully this will help someone else who encounters this.

Posted : 28/07/2021 2:47 pm
BogdanH
(@bogdanh)
Estimable Member

Thank you for reporting -this might be valuable info in future.

Mini+ with Bondtech upgrade & modified firmware...
Posted : 28/07/2021 2:52 pm
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