Raise limits for "TRUE BED LEVELING"

peirof

Hi,

on a CoreXY printer, with 3 independent Z motors, I am trying to use "TRUE BED LEVELING", but when I try, I get this error message.

G32 Error: Some computed corrections exceed configured limit of 5.00mm: 1.912 -6.511 4.985

I understand that it is because the limits for the "TRUE BED LEVELING" are exceeded

Where those limits are increased? (5 mm seems a bit fair to me)

engikeneer

You set the limits in your M671 command, using the S parameter

https://duet3d.dozuki.com/Wiki/M671

Default is 1.0mmm, so I;m guessing you've already modified that in your config?

General reason for keeping your limit set low is because if there is an issue with the measurements (probe fails, or you have the Z motors mapped incorrectly), it could attempt to do a massive (but incorrect) correction and cause significant damage to your bed.

Personally I set my limit at 2.0mm. I only ever exceed that if there is something mechanical I have done (e.g. messed with the Z steppers and moved them). I'd then power the machine back off and slowly hand rotate the steppers to get the bed more level, before powering it back on and trying G32 again. At -6.5mm & +4.9mm, your bed must be on a very big angle!

fcwilt

@peirof

Increase the limit to see if you can avoid the error.

Then verify that the bed is actually becoming more level.

If the configuration for bed leveling is wrong the bed can become less level.

Frederick

peirof

@fcwilt the bed is very inclined, it is the first time that the printer is put into operation... if this parameter is so delicate, another thing that I can do is do, it is an approximate leveling "by hand", turning the leadscrew manually until is in the limits... and then execute the "TRUE BED LEVELING"

fcwilt

@peirof

Given the limits of bed leveling in coping with a seriously out of level bed you might consider adding Z endstop sensors to each Z axis.

Doing this allows you to home Z using the endstops sensors instead of the Z probe. Then you can use bed leveling to fine tune the bed.

Here is a quick-and-dirty video of my printer. I intentionally put the bed seriously out of level.

Bed Leveling Video

Frederick

oliof

@fcwilt how is that configured? I'm intrigued and would like to know more.

fcwilt

@oliof said in Raise limits for "TRUE BED LEVELING":

@fcwilt how is that configured? I'm intrigued and would like to know more.

All you need is the following with the appropriate pin names for your hardware.

M574 Z1 S1 P"!duex.e2stop + !duex.e3stop + !duex.e4stop" ; configure three Z endstops

Also the order of the endstops has to match the order of the Z steppers as that determines which endstop is checked for a given Z stepper.

Frederick

oliof

@fcwilt Super nice and easy to set up, thanks for indulging me (-: I'll be building another triple Z setup where I will give this a go.