bed not level - mesh bed leveling does not compenstate
 
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bobc
 bobc
(@bobc)
Reputable Member
RE: bed not level - mesh bed leveling does not compenstate

I've noticed the bed leveling doesn't do a great job with my bed. I can see the Z moving to compensate depending on the position on the bed, but the first layer still is somewhat uneven.

I suspect there is a sampling error, I'm not sure what algorithm is used in the Mini firmware, but it may not be sufficient to map peaks and troughs. The general rule of sampling is you need at least twice as many samples as the highest frequency.

I've never seen anyone do a proper calibration of the mesh bed leveling. You would need to compare the result with an accurate measurement by something like a dial gauge.

Posted : 19/09/2020 8:49 am
Elbkind
(@elbkind)
New Member
RE: bed not level - mesh bed leveling does not compenstate

I fixed this with some steel springs instead of the 6mm spacers under the heatbed. The fine tuning takes a while, but the results are good.

Posted : 25/09/2020 8:54 pm
mafredri
(@mafredri)
Active Member
RE: bed not level - mesh bed leveling does not compenstate

When BML doesn’t seem to be doing the right compensation, two things can help:

  1. Pre-heat the bed and let it sit at target temp for 5 minutes before performing BML
  2. Pre-heat the PINDA/MINDA probe to 35C before BML
  3. Combine 1. & 2.

Granted, these are my experience from my MK3S, I don’t have a Mini, so can’t guarantee it’s applicable.

The reason 1) can help is that the heat bed will expand during heatup and there’s no guarantee it won’t keep doing it after hitting target temp. The firmware assumes the bed does not change shape which can lead to wrong compensation. Similarly for 2) the heated bed will heat up the PINDA probe during BML which means that first and last point can be probed at vastly different PINDA temps and firmware does not calibrate for the lower spectrum (<35).

Some people don’t seem affected by these things though, YMMV.

Posted : 26/09/2020 4:12 am
bobc
 bobc
(@bobc)
Reputable Member
RE: bed not level - mesh bed leveling does not compenstate
Posted by: @mafredri

When BML doesn’t seem to be doing the right compensation, two things can help:

  1. Pre-heat the bed and let it sit at target temp for 5 minutes before performing BML
  2. Pre-heat the PINDA/MINDA probe to 35C before BML
  3. Combine 1. & 2.

Granted, these are my experience from my MK3S, I don’t have a Mini, so can’t guarantee it’s applicable.

The reason 1) can help is that the heat bed will expand during heatup and there’s no guarantee it won’t keep doing it after hitting target temp. The firmware assumes the bed does not change shape which can lead to wrong compensation. Similarly for 2) the heated bed will heat up the PINDA probe during BML which means that first and last point can be probed at vastly different PINDA temps and firmware does not calibrate for the lower spectrum (<35).

Some people don’t seem affected by these things though, YMMV.

If you did have a Mini, you might realise steps 2 is not possible, the MINDA does not have a temperature sensor. This has been the subject of a lot of discussion in the Mini forums.

Good point about the bed temp though. I have a delay in my start gcode which helps a little.

Posted : 26/09/2020 8:21 am
Martin Majewski
(@martin-majewski)
Trusted Member
RE: bed not level - mesh bed leveling does not compenstate

It’s nearly the end of 2020, we have FW 4.2.1 and still MBL is not compensating for the poorly machined bed. I cannot use the entire bed, not even get the 1. layer calibration to stick on the right hand side of the bed. ☹️

 

 Cheers,

 Martin

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Posted : 30/10/2020 12:50 pm
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