M558 parameters with Duet

Hi all,

Just one precision with M558 command.
H parameter specifies at what height must be the position of the probe to start its measurement with G32 ? Default is 3mm. Is it right ?

Best regards,

Laurent

Yes, that is correct. The default 3mm is OK when the printer has already been calibrated approximately, but I recommend using a higher value for initial calibration.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I was more puzzled by the P500 value.
Is it the hysteresis of the probe?
What unit is it? Is more better or worse?
-Olaf

The P value is the probe threshold at which the head is deemed to be at the trigger height. The correct value depends on your type of Z probe:

- If you use a Z probe with an analog output, choose a value appropriate to the probe.

- If you use my IR sensor, choose 500. This is because my sensor outputs 465 when approaching the trigger height, and 535 at the trigger height. The firmware senses the 465 value (because it is more than 90% of 500) and slows down the probing speed when it sees it.

- If you use a switch, then it will output 0 when not triggered and 100 when triggered. So again I suggest a value of 500. But you can use a lower value (e.g. 50) if you want a faster response.

Other M558 parameters in 1.09k-dc42 and later firmware include F (probing speed) and T (travel speed between probe points).

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hello,

About probing speed and travel speed between probe points ,the speed of execution has been an influence on accuracy ?

Hello,

After some G32 calibration and config.g updated, I obtain the following result when I launch one G32 :

Calibrated 6 factors using 13 points, deviation before 0.048 after 0.044

Is it correct and accuracy enough ?

Quote
lolocaledo
About probing speed and travel speed between probe points ,the speed of execution has been an influence on accuracy ?

The travel speed should not be so fast that you lose steps. If the probing speed is too fast, you may lose accuracy because the motors can't stop fast enough. If you are using my IR probe on a Duet, then preferably use a probing speed that is slow enough that you can see it slow down as it approaches trigger height. Slowing down probing speed may increase trigger height a little because of the time delay introduced by the averaging filters.

Quote
lolocaledo
Calibrated 6 factors using 13 points, deviation before 0.048 after 0.044

That's good IMO, and it also says that running calibration again only improved the deviation very slightly. Your homing switch and Z prove repeatability may not be better than 0.04mm anyway

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

IMHO, trying to tweak the probe speeds isn't useful. I changed config.g to match the new found parameters. Now I have a deviation of 0.04 before calibration and 0.03x after.
Don't need to calibrate every time.
-Olaf