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[BUG] UBL G29 multiple probing not improving accuracy #22506
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Whenever there are homing or leveling issues, we now ask everyone to follow a standard procedure to gather more information so that we're not just taking stabs in the dark. Here is the boilerplate:
Repeat this procedure, if needed, to demonstrate inconsistencies. From these logs we should hopefully get a better idea of what's going on with your machine. |
done. Debug info attached + DSView logic analyzer file.
|
According to your log you are not running
It looks like the probe is simply returning almost the same exact value on each probe, indicating that you simply have a very consistent probe. A test with Your probe's Z offset could be improved. The probe result closest to 0 is -1.8. So you should subtract 2 from your probe Z offset to try to and get all your points close to 0. |
HMMM. Yes probe is pretty precise, see M48 results in the "Bug Description"
or am I totally on the wrong track? |
This issue has had no activity in the last 60 days. Please add a reply if you want to keep this issue active, otherwise it will be automatically closed within 10 days. |
This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs. |
Did you test the latest
bugfix-2.0.x
code?Yes, and the problem still exists.
Bug Description
Setup is a custom large format machine with custom electronics. The printer is working. ZPROBE is an inductive sensor with clean filtered signal and consistent results (M48: Mean: -3.165667 Min: -3.169 Max: -3.163 Range: 0.006, Standard Deviation: 0.002630).
I wondered about relatively wide varying probe values and tried to improve accuracy with multiple probing (x2, x3) but this has shown a strange behavior. Seems like only the first probing is a "real" measurement, the 2nd/3rd (at the same position) is always very close to the theoretical value. See Logic Analyzer measurement attached.
Background: since its "large format" (ca 700x700mm) a warped bed is very likely, 2mm between edges is realistically. UBL can manage this (proven prints). However, sometimes probing values are way off. You hear this on the Z-Motor when its moving much shorter to the ZProbe than usual. I wanted to identify the problem and found this with ,ultiple probing.
G29 T mesaurements are:
Probing step count 'til trigger of a triple probing run was:
...
Bug Timeline
tested on current version, very likely on older versions
Expected behavior
with multiple probing 2/3 very close measurements
Actual behavior
first measurement seems real distance, 2nd / 3rd measurement very close to Z_CLEARANCE value
Steps to Reproduce
G29 P1 T and count Z stepper pulses in to-probe direction until probe triggers - should be multiple times very close
Version of Marlin Firmware
2.0.9.1
Printer model
custom
Electronics
custom LPC1768
Add-ons
No response
Your Slicer
No response
Host Software
No response
Additional information & file uploads
configs.zip
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