Issue with probing: second approach skipped/aborted

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vincent_konglomerat
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Joined: Thu Sep 26, 2024 6:11 pm

Issue with probing: second approach skipped/aborted

Post by vincent_konglomerat » Wed Jan 29, 2025 8:14 am

We use a fixed probe for measuring the z-offset during initialisation or after tool changes. In order to get more consistent results, we let our z-axis approach the probe twice, once with F300 and then again with F100 after a small retract move.

However, sometimes the probing skips the second approach (?) and just retract z to the highest position.
There is no error code displayed and the script seems to continue as if nothing happened (G92 and G53).
This is the probing snippet we use in our program-start and tool-change scripts:

Code: Select all

G91 (put the machine in "incremental distance mode")

F300 (search speed)
G38.2 Z-87 (probe down until the plate is touched or until Z has moved by -87mm)

G0 Z1.5 (retract 1.5mm up)

F100 (second approach with lower search speed)
G38.2 Z-2

G92 Z20.4 (sets Z0 = surface table)
It is a huge issue for us, because whenever this happens, Z0 is suddenly shifted off by up to 2mm.
We are basically unable to use toolchanges during programs now, since every one of them could cause the issue, requiring us to stop the current program to repeat the probing.

Does anyone have an idea what might cause this sudden abort/skip of the second probing approach?
What we tried so far is slowing down the Z motor, and adjusting the retract height between first and second approach. So far, this was not successful and we are still unable to consistently reproduce the issue.

I managed to take a video of a faulty probing, let me know if you want to see it

cheers
Vincent

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Doug
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Re: Issue with probing: second approach skipped/aborted

Post by Doug » Sun Feb 02, 2025 9:41 pm

Are your sure that your switch fully opens with the 1.5mm retract? You might want to try retracting a litter further before the second probe.

vincent_konglomerat
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Joined: Thu Sep 26, 2024 6:11 pm

Re: Issue with probing: second approach skipped/aborted

Post by vincent_konglomerat » Mon Feb 03, 2025 5:44 am

yes, that was the first thing we tested when the issue came up. Tried heights up to 10mm, but it never seemed to solve the issue and it still skipped the second approach roughly every third or fourth attempt

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Doug
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Re: Issue with probing: second approach skipped/aborted

Post by Doug » Tue Feb 04, 2025 8:51 pm

Have you tried adjusting the 'input-debounce' setting on the SETTINGS-> I/O page?

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Doug
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Re: Issue with probing: second approach skipped/aborted

Post by Doug » Tue Feb 04, 2025 8:55 pm

Feel free to call me at 707-559-8539 if you want me to help you via the phone.

Doug

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Doug
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Re: Issue with probing: second approach skipped/aborted

Post by Doug » Wed Feb 05, 2025 6:52 am

Try putting in a dwell command (G4) just before the second downward probe. For instance 'G4 P2' would cause the system to wait for two seconds. If this works, you can try reducing the pause time the shortest value that works.

I think this might have something to do with the 'input-lockout' time that can also be adjusted on the SETTINGS->I/O page.

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