Mesh bed leveling going haywire...  

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jochen.h
(@jochen-h)
Active Member

Been super happy with the Mini (after I threw the no-PLA-will-stick-to-it textured bed in a corner and switched to the smooth one). Prints as nice as my MK2.5SS (had that since the MK2 first came out, i.e. I've been around the block ;-).

Yesterday, out of the blue, the mesh bed leveling started going wonky on the left side of the bed. All fine for the first three points on the right. For the remaining points on the left, it just goes up two separate steps and doesn't come back down. Once it goes to the next row, it keeps going up for the first points (on the left). When it gets to the middle point, it comes down to the bed and everything is peachy. It does the same thing on the left side of the bed for every row. As you can imagine, the resulting calibration is useless... 😉

No physical changes or even a reboot between when it was working and when it first failed. I had flashed the printer with 4.0.1 when I first got it. The current behavior started out of the blue. Printer printed fine, was idle but switched on for about 20h, calibration for next print showed the above behavior. Printer also hadn't been moved in between.

Things I've tried

  • Reboot - No change
  • Factory reset - No change
  • PINDA is "non-wiggleable"
  • Tried to re-flash firmware but it doesn't give me the option when I put either the 4.0.0 or 4.0.1 FW on the USB stick

Any ideas? Thanks a bunch in advance!

Best Answer by jochen.h:

Customer support confirms broken MINDA cable. They are sending me a new one.

Thanks a lot for your help!

...
Posted : 28/12/2019 11:28 pm
Bodo
 Bodo
(@bodo)
Estimable Member

Sounds like this is your bug:
https://github.com/prusa3d/Original-Prusa-MINI/issues/4

Best check is to move the MINDA wire, and to see if the MINDA light flickers. If yes, open a ticket with chat support, and they will see you right (worked for me).

This post was modified 1 year ago 3 times by Bodo
Posted : 28/12/2019 11:45 pm
jim.n2 and jochen.h liked
jochen.h
(@jochen-h)
Active Member

Thank you! I bet that's it. The print before it started happening was to max print volume for the first time. That must have tweaked the cables.

My PINDA doesn't flicker when I wiggle the cable, though. 

Took a video of the behavior.

Mesh bed leveling

Thanks again and will contact support.

...
Posted : 29/12/2019 2:14 pm
jochen.h
(@jochen-h)
Active Member

Customer support confirms broken MINDA cable. They are sending me a new one.

Thanks a lot for your help!

...
Posted : 29/12/2019 2:37 pm
Bodo
 Bodo
(@bodo)
Estimable Member

Result. The linked issue report above also contains a temporary hack to bridge the waiting time for the new sensor. I'm hoping the error won't occur again with the new MINDA. If you haven't disassembled the textile-sleeved cable harness yet, maybe check the three cable ties at the sled if they are very tight, or if they can be rotated in place by hand.

Posted : 29/12/2019 4:04 pm
tzickus
(@tzickus)
New Member

I have the same exact issue!   My minda probe does not flicker either.   I have a new probe on the way, I really hope it fixes it.

Posted : 31/12/2019 4:16 pm
Bodo
 Bodo
(@bodo)
Estimable Member

After I repaired mine (the MINDA cable) provisionally (new replacement MINDA due to arrive tomorrow), I'm experiencing issues that could be related to the MINDA's history:

Actual bed leveling output is randomly different after each go for a couple of - what unit is that actually that you set in 1st layer calibration?? One thing I know: it's not millimeters! Let's call them Prušons (Pš) for now - after every bed leveling, there is a difference to the one I initially calibrated of about +/-0.400Pš.

A new calibration is worthless, because the printer does bed leveling before every print with a new 1st layer height.

Hope the new MINDA fixes this tomorrow.

Posted : 02/01/2020 4:55 pm
jochen.h
(@jochen-h)
Active Member

I think they are in millimeters 😉

Could be an issue with the temperature sensor wires. With the original PINDA, I’ve seen variations almost that big when restarting a print inside an already hot enclosure. Drove me nuts 😉

...
Posted : 03/01/2020 12:10 am
PJR
 PJR
(@pjr)
Moderator
Posted by: @jochen-h

I think they are in millimeters 😉

Could be an issue with the temperature sensor wires. With the original PINDA, I’ve seen variations almost that big when restarting a print inside an already hot enclosure. Drove me nuts 😉

The MINDa does not have temperature compensation (cost constraint) so you have to be very consistent when starting a print.

If the probe is at different temps, then the Live-Z will need to be changed slightly (I have variations of ± 0.2mm).

 

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…...
Posted : 03/01/2020 10:58 am
Crawlerin
(@crawlerin)
Prominent Member

@pjr

Thanks, people suspected that. This may explain why my live-z oscillates somewhere between -1.700 - -1.400 each print. I was starting to think I am clumsy and do not know how to set it properly. Makes watching first layer all the more important.

Posted : 03/01/2020 3:00 pm
Crawlerin
(@crawlerin)
Prominent Member

Sorry I meant - 1.070 to - 1.040, which is not as huge. Them decimal points 😣 

Posted : 04/01/2020 4:40 pm
bennydesign
(@bennydesign)
New Member

The MINDa does not have temperature compensation (cost constraint) so you have to be very consistent when starting a print.

If the probe is at different temps, then the Live-Z will need to be changed slightly (I have variations of ± 0.2mm).

 

Peter

But then the firmware needs to be changed so that it waits longer before the mesh leveling to have the probe reach a certain and hopefully constant temperature for every print. Maybe MINDA wasn't such a good idea after all ...  

Posted : 06/01/2020 2:08 pm
Talryyn
(@talryyn)
Active Member

My friend just got his replacement MINDA and the machine will still not work with the replacement.  🙁  He is sending another video to support now.  He is on version 4.01 and that is when it stopped working.

I am still on 4.0 with over 300+ hours on the machine. 

This post was modified 1 year ago by Talryyn
Posted : 07/01/2020 12:32 am
Trailer Alarms
(@trailer-alarms)
Active Member
Posted by: @john-m30

My friend just got his replacement MINDA and the machine will still not work with the replacement.  🙁  He is sending another video to support now.  He is on version 4.01 and that is when it stopped working.

I am still on 4.0 with over 300+ hours on the machine. 

Got my replacement and still having issues. I'm on 4.0.1

Posted : 07/01/2020 2:07 am
Talryyn liked
tzickus
(@tzickus)
New Member

I have 4.01 and my replacement probe is working so far.  

Posted : 07/01/2020 12:35 pm
jochen.h liked
Bodo
 Bodo
(@bodo)
Estimable Member

My replacement MINDA fixed the issue.

Posted : 07/01/2020 10:16 pm
jochen.h liked
jochen.h
(@jochen-h)
Active Member
Posted by: @bennydesign

The MINDa does not have temperature compensation (cost constraint) so you have to be very consistent when starting a print.

If the probe is at different temps, then the Live-Z will need to be changed slightly (I have variations of ± 0.2mm).

 

Peter

But then the firmware needs to be changed so that it waits longer before the mesh leveling to have the probe reach a certain and hopefully constant temperature for every print. Maybe MINDA wasn't such a good idea after all ...  

Oh, very sad to hear that, Peter. I had not realized that was the case 🙁 I really hope there's an upgrade path for that. I would have paid extra for it. Without it, ABS in an enclosure will be the same PITA as on the MK2...

Lyle, they did modify it. The Mini does the bed leveling with the hot end at 170C. I was pleasantly surprised. It's something I've been doing on the MK2.x for years to reduce the temp effect on the sensor (with ABS in an enclosure at 40+C). Another thing that helps is raising the hot end while the bed is heating. That would be a tweak you could do to the Mini start code. 

The variability also explains my issues with the textured sheet. I could never get that to stick PLA consistently. I then switched to my "ABS setup" of plain PEI, roughed with green kitchen sponge, and cleaned with acetone. That'll stick PLA even if your Z height is only roughly in the ballpark.  

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Posted : 07/01/2020 11:02 pm
MatthewW
(@mattheww)
New Member

I appear to have this exact same issue on my Mini.  Video of the problem:  

It also began after my first large-volume print.

I emailed Prusa when I posted that video, six days ago, but still haven't heard anything.  I'm hoping this is still just the holiday break/backlog causing some delays.  A big reason I added a Mini was to have something that just worked out of box, without constant attention and replacement of parts :/

Posted : 08/01/2020 3:59 pm
Bodo
 Bodo
(@bodo)
Estimable Member

@mattheww I emailed support as well, because the chat was closed in the holidays. When the chat opened, I also used the chat, and got helped immediately. Email was replied to days later after my issue was closed. I guess chat is more responsive (and also better for quick help).

Posted : 08/01/2020 8:04 pm
Trailer Alarms
(@trailer-alarms)
Active Member

Still having issue with new MINDA sensor. Now they think it an issue with my Y axis causing issues with my Z axis.

Posted : 08/01/2020 8:22 pm
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