SET_SKEW crashing Klipper

General Discussion
1

Basic Information:

Printer Model: Voron 2.4 350x350
MCU / Printerboard: BTT Manta M8P
klippy.log

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Describe your issue:

…

Trying to set [skew_correction] but when I send command:

SET_SKEW XY=141.319,141.524,199.419 XZ=141.444,141.399,199.419 YZ=141.323,141.519,199.325

Klipper crashes and I get this in the slippy.log:

Internal error on command:"SET_SKEW"
Traceback (most recent call last):
  File "/home/pato/klipper/klippy/gcode.py", line 211, in _process_commands
    handler(gcmd)
  File "/home/pato/klipper/klippy/gcode.py", line 137, in <lambda>
    func = lambda params: origfunc(self._get_extended_params(params))
  File "/home/pato/klipper/klippy/extras/skew_correction.py", line 115, in cmd_SET_SKEW
    setattr(self, factor, calc_skew_factor(*lengths))
  File "/home/pato/klipper/klippy/extras/skew_correction.py", line 15, in calc_skew_factor
    side = math.sqrt(2*ac*ac + 2*bd*bd - 4*ad*ad) / 2.
ValueError: math domain error
Transition to shutdown state: Internal error on command:"SET_SKEW"

Any suggestions?.

klippy.log.zip (1.0 MB)

2

Found something interesting. I went to the Klipper documentation page and there is sample GCODE:

SET_SKEW XY=140.4,142.8,99.8 XZ=141.6,141.4,99.8 YZ=142.4,140.5,99.5

This works!.

Mine is:

SET_SKEW XY=141.319,141.524,199.419 XZ=141.444,141.399,199.419 YZ=141.323,141.519,199.325

I am getting these values from the excel calculation sheet provided by Vector3D, the maker of Calilantern, the model I am using to calculate skew.

I noticed that the third value for every plane on his calculations is in the hundreds and not tens. If I take out the one before each third value, it works. Will try to contact the maker of Calilantern to see if he can help me.

3

Are you sure you made the correct measurement for the third value?
It appears to be as twice as large as it should be.

1 Like
4

Not sure al calculations are correct. Measurements are but the excel document provided by Vector3D might have a bug in it. Checking with developer now. I have the suspicion that it might be related to the fact that I printed the Calilantern model at 200% scale to be more accurate on my 350x350 Voron 2.4.

5

Your values are just wrong causing the module to crash during calculation.
I think the 199.325 should be more like 99.325.

If you read through here and check the picture you should find some hints:
https://www.klipper3d.org/Skew_Correction.html?h=skew#take-your-measurements

Your last value is AD.
If we use this as reference for the legs of an right-angled triangle we can use the Pythagorean theorem:

AC² = 2 * AD²
AC² = 19730.911250
AC = 140.4667

You can solve this for AD as well if you use AC or BD.

6

Thank you. I heard from the developer of the Calilantern and its spreadsheet and it was, as all said, a calculation error in the spreadsheet once the model was scaled to other than 100% which I did.

2 Likes
7

Thank you for the feedback!

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8

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