G30 S-1 Probeheight differences



  • Hey all,

    Today I turned on my printer again after 2 months of waiting until I was ready again to fight some symptoms.

    I use a CR10S with a BLTouch Z probe.

    When probing for Z-Stop Height with the command G30 S-1 it comes up with a value of 1.355mm

    When I raise my Z axis for 5mm and then probe again it gives me 1.390mm
    When I raise my Z axis for 25mm and then probe the stop height again it comes with 1.330mm

    So when I raise my z-axis higher the probe stopping height gets lower.
    but when I even get higher to 50mm it starts to get lower. 1.357mm stop height.

    Can anyone tell me where this deviation comes from? at sometimes it can be like 0.1mm difference, and when I am printing at 0.15mm layer height it can ruin my print XD


  • administrators

    Some bed heaters affect the BLTouch, so try adding parameter B1 to your M558 command to turn the heaters off during probing. Another possible cause is probing too fast, so try reducing the F parameter.



  • hi,

    The bed is off, and probe speed is super slow, tried those already.

    could it be that it has something to do with Zrods that are not straight?
    or something else? maybe stepper motors not accurate enough?


  • administrators

    I am not an expert on BLTouch, but I understand that they don't always give consistent results. Are you sure that the value you get depends on how high you raise the probe, and doesn't just have a random element?



  • yeah, I'm sure.

    of course, it deviates a little bit but the variables are almost the same every time.
    it is reoccurring in the way I described it. really strange to be honest.

    Same occurs when I try to level the nozzle to the bed with a piece of paper, in steps of 0.05mm down until it makes contact with the paper. but when I go up, it takes more 0.05mm steps up, then what it did while going down.

    Down
    0.00mm - no contact
    -0.05mm - contact

    Up
    -0.05mm - contact
    0.00 - contact
    0.05mm - still contact
    0.10mm - no more contact with the paper

    that's also occurring


  • administrators

    @nelisgast said in G30 S-1 Probeheight differences:

    yeah, I'm sure.

    of course, it deviates a little bit but the variables are almost the same every time.
    it is reoccurring in the way I described it. really strange to be honest.

    Same occurs when I try to level the nozzle to the bed with a piece of paper, in steps of 0.05mm down until it makes contact with the paper. but when I go up, it takes more 0.05mm steps up, then what it did while going down.

    Down
    0.00mm - no contact
    -0.05mm - contact

    Up
    -0.05mm - contact
    0.00 - contact
    0.05mm - still contact
    0.10mm - no more contact with the paper

    that's also occurring

    That's called backlash.



  • haha okay thanks for giving it a name, now I can investigate more.



  • searched for Z axis backlash, but there is nothing to be found, how do I fix this 😄



  • @nelisgast anti-backlash nuts



  • thanks will look into that 😉


 

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