Auto Bed compensation not correct



  • I've got a strage issue here with the auto bed configuration. The Z-Offset for the IR probe is set to 1.18 so when i do auto homing it moves the Z-axis to 1.18 and when i start the auto bed compensation the first point comes to 1.18 as well. Then for the scond point it comes to about 2.22 which is really strange because when i do it manually the IR probes light comes on when I am at 0.97.
    The really strange thing is that points 2-5 are all in about the same height but the first point is always much lower. No matter what I set for Z-Offset the difference between the first and third point is always more thant 1mm. Why is that?



  • Does no one have an idea?


  • administrators

    What sort of 3D printer is it?



  • It's an Ultimaker Original.



  • i have also noticed some inconstancy with my ir probe. I have a large format delta, using duet wifi, with a glass bed. I have tried sand blasting the backside of the glass, along with various colored paper glued to the back.
    I noticed that my probe points vary .2 to .4 mm in the same spot. and my calibration factors are all over the place every time a run a auto calibration i have also noticed that the value given on the DWC is very erratic at some heights, and almost none responsive at others. When lower the probe close to the surface, i will start getting erratic reading 180 and 300, as i bring it even closer it will go back to 0. as i step it closer, it will eventually jump to 466 at about 2mm above the bed and stay there as i continue to bring it down, it will then switch to 535 and turn the red led on and stay a that reading until it is at Z0. i have M558 set to mode 1, i get 4 led flashes when it powers up. both emitters are producing a light when viewed threw a camera and my power is 3.3v ground is 0 and the sensor voltage is also erratic when slowly bringing it close to an object.
    is this normal, or bad sensor. Its only 2 months old.


  • administrators

    Those readings of 180 to 300 indicate that you have a bad connection in your IR sensor wiring, or just possibly a cracked resistor on the sensor. You should only get readings that are very close to 0, 465 and 535.



  • Yes, my readings are correct. They re around 535 when triggering the bed to stop. Like I said, it all works correctly when I'm doing it manually. I just wonder why the auto bed compensation algorithm works and why the readings for points 2-5 are close to each other but way higher than point 1.



  • Still nothing to solve this problem?


  • administrators

    Have you tried measuring the probe trigger height at different places to make sure it is consistent? For example, measure it at the first and third points.


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