while doing G32, it press on the bed at some points.

edited May 2019 in Extruder & Bed
I don't know if the Title is clear, but so far I have been unable to solve this.
The first row on the grid (X20), probing is normal.
On the following Rows, for Y20, it continue pressing the head on the bed, (the probe is already on), so the results for these points are wrong (+- 1mm). On the other points, results are looking OK.
When I do Z homing, it looks perfect, the head a coupe of tenth of millimeters above the bed.

I am not sure which parameter I need to change to get proper measures everywhere.
Right now I have Z-Probe Height 4.00, Max-ZProbe bed dist 10.00

Thanks for your help (I Had this working fine before, but I changed the probe and all parameters have to be adjusted)


  • Only one i can think of is


    make sure this is set high enough to un-trigger the probe , i have mine at 3.

  • I forgot to say I had already done this. I solved this my lowering a little bit the probe. Still found it strange that it was only on some points
  • You do G32 with 20x20 points? That is a bit overkill as only 3 points are required for bed. All additional points are just used to make it a regression plane through points measured. This also explains why a few points with wrong values have not much influence. Normally 3x3 is good enough for G32. If you need bump correction you do that with G33 where more points can make a difference.

    Does the probe return to Z=10 for each point when switching? Normally you should get an error in log if z probe does not switch off where expected. So it will stop when z probe H is detected. If it still gets a bit lower the signal is not coming to the board. Can it depend on the probe type? E.g. inductive probes can be influenced by bed heating or changes in conductive material.
  • edited May 2019
    Thanks for your answer. No, I do 5 x 5 points. And yes, I have a number of problems, it does not seem always consistent. My probe is a LJC18A3-H-Z/BX which is capacitive, if I am not wrong. I followed the instructions here https://www.repetier.com/documentation/repetier-firmware/z-probing/ but I am really not sure what I got as Z-PROBE_HEIGHT is correct: it give me 2.038, but the physical distance is at least 5mm more than that. Should I physically lower the probe?

  • Best way to calibrate z probe height is using G30 and a metal block with known height. Run G30 see what distance it returns, move that distance would be block height and compare with block so that block is just not touching extruder nozzle. The correction between the 2 points is what you need to correct z probe height.

    Then test same at a position where you know it measures wrong. See if height is measured differently there. Then you know something is influencing the z probe. Make sure bed is not heating when testing. That is known to influence inductive probes. You also need a metallic surface above the heater or you measure against the heater spirals and they have parts without metal so it influences measurements as well.

    Also try repeated G30 to see if probe always measures the same distance so repeatablility is given. If not repeatable, decrease sensitivity so it needs to come closer.
  • Thank you, I appreciate the help. This gives me a good roadmap.

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