Auto Bed Leveling went bad

BlueDust

@Phaedrux
I haven't tried to manually fix it until yesterday and it was just so I could print, and didn't try out running G32 again. Printing right now...

I can run G32 over and over again, and the more I run it the more accurate it becomes with smaller adjustments to make it level, but it is still at a bad angle.

Thanks for mentioning the screw locations don't have to be perfect... I keep trying to re check them and can change them maybe 1 or 2 MM based on where the nozzle when I check it. I just changed where home X/Y are (a few mm in so they don't hit the Z screws when homing, and possibly when printing if its a large object).

BlueDust

I kept tweaking everything, and now have it working "well enough", that for most printing attempts, if I bed level 3 times, and then run bed level compensation its "good enough". This used to work every time with running G32 one time, unless it's adjustment was outside of the set range....
But with all the trouble I have been having, this isn't so bad. I will close this issue if I can get another print or two out.
Let me know if you guys have come up with any other ideas.
Thanks

Phaedrux

So if it's not applying enough correction on each run, you can increase the amount it can apply with the M671 S parameter.
https://duet3d.dozuki.com/Wiki/Gcode#Section_M671_Define_positions_of_Z_leadscrews_or_bed_levelling_screws

The default is 1mm. Try increasing it to 2?

dc42

@BlueDust, you might want to try 4 points instead of 3, one near each corner of the bed.

Are you sure that the way that the bed is attached to the leadscrews provides sufficient flexibility for the leadscrews to move independently by a sufficient amount to correct the tilt?

BlueDust

@Phaedrux
I have the S settings set to 5... Default was 1. I made this change shortly after I set it up the first time so it could fix issues up to 5mm out of level.

BlueDust

@dc42
I can adjust the screws by hand very easily.
Also, the tilt is generally ~.5mm off from the two furthest measurements from each other.

I just setup 4 point instead of 3, in the corners and now playing around with it. I will have to get back to you on any improvement.

Thanks!

BlueDust

@dc42
I am now running bed leveling with 4 points and seems to be working much better.
Sometimes I find I still need to run bed level 3 times, but it is less often then it was before.
The biggest issue I have now, is that the bed is always lower than Z, and the printer keeps telling me to home Z. I do, and when I run Mesh Compensation again, it's still below Z enough for it to complain... again.
I end up printing anyways as it's close enough and doesn't have any problems printing the 1st layer.

Phaedrux

What your full order of operations for leveling and homing before you print?

BlueDust

@Phaedrux

This is the script I run to bed level. After you helped me to run Mesh Bed Compensation with multiple Z probes for accuracy, I added G29 to the script.

G28
G32
G29
G0 X125 Y0 Z25 F6000

Another thought. Not sure if this matters, but I home Z in the center of the bed. Should I be doing that at the same corner I home X and Y?

Phaedrux

Homing Z to bed center, or ideally a point close to center that is also a point probed during G29.

BlueDust

@Phaedrux
This printer has been causing me a lot of quality problems since Dec of 2019 where I sort of let it rest (small single object TPU/TPE jobs printed fine) for a year after Covid happened before putting more (but random) time in to troubleshooting it.
Over the last few years replaced all the major parts including this last week replaced the Duet2 with a Duet 3 and 1lc tool board. Once I got everything for the most part working (ie printer could print), I started working on Auto Bed Leveling again, and was again having trouble that reminded me about this post. I reread your question a few times (asking if I run leveling multiple times in a row does it get worse) thinking it was a clue. But as I never reran auto bed leveling more then once in a row, I didn't see this happen when I was testing, as the bed would get so far out of level that the BL Touch would give up or already be triggered when it went to a location to probe for the bed.
Turns out this was the problem the printer was having after I moved to the Duet 3. Every time I ran it, bed leveling got worse in the same way. Focusing on what could cause this, I realized that the Z motors were not associated with the correct locations.

I am not sure on what caused the problems with this printer on the Duet 2, but think the board is OK and it was just some calibration that got out of whack when trying to print a handful of different filaments that ended up being bad... And wasn't able to figure out what I did. Going to the Duet 3 forced me to redo everything, gave me an Accelerometer for Input Shaping and all the other goodies I get when using an SBC. So I am not complaining.

And as always. Thanks for the help!