1st Layer height -



  • Something odd .. really odd with my systems Z height using 3.2 beta 3.2

    Machine is a core XY, Duet3, Z height measured using Pinda probe, triple independent z axis (bed supported on kinematic mounts, I am not using a Pi at this time.

    I did a print, something wasn't right I was getting a lot of filament building up on the nozzle during the first layer of a print and yet in some places filament wasn't deposited as expected. Pretty characteristic for PETG when the nozzle is too low.

    I therefore decided to verify the Z axis settings. In a test print using a single 0.15 layer square the 1st layer was 0.0660 - it was supposed to be 0.15. The G31 code at this time was G31 P1 X-21 Y0 Z0.739 C0.002 S29 H3

    Changed this to G31 P1 X-21 Y0 Z0.759 C0.002 S29 H3

    and the 1st layer height was .... yup 0.0660

    changed to G31 P1 X-21 Y0 Z0.859 C0.002 S29 H3

    and the 1st layer height was ... yup you guessed it 0.0660 ....

    I have done a measure on the actual trigger height using a feeler gauge and it is 0.88mm, I have verified the Z calibration (M92 X160.00 Y160.00 Z1600.00 E400.00) these are 1.9 degree steppers on a Tr8x2 pitch single start leadscrew (E3D)

    The calibration height is measured using a high end Mitutoyo micrometer (no it is not a fake)

    Understand that the original G31 P1 X-21 Y0 Z0.739 C0.002 S29 H3 was deliberate to ensure adequate nozzle height for PETG which does not like to be squished. I have verified that Z0 really is 0 when the nozzle time touches the bed.

    Anyone care to offer a clue why the layer height is not as expected, why is the machine not calculating the appropriate height for the first layer ?

    G29 S0
    182 points probed, min error -0.081, max error 0.087, mean -0.004, deviation 0.033

    G32
    Leadscrew adjustments made: 0.091 -0.086 0.065, points used 4, (mean, deviation) before (0.011, 0.083) after (-0.000, 0.047)

    DUMMY ALERT - make sure you don't hit the imperial selector on your fancy micrometer and jump to the wrong conclusion - 0.0660" = 0.167mm .... doesn't explain why the nozzle is picking up filament but it isn't the Z height - this isn't a beta code problem-


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