Can't get the nozzle height correct



  • I have just had to take the nozzle out of my E3Dv6 for cleaning, and now I can't get the height right. Regardless of the value I put in the config.g file's G31 command, after the Duet is reset the nozzle comes down a little too far and grabs the paper too tight. Lifting the nozzle 0.3 gives me exactly the clearance I want. What's confusing me is that it seems that no matter what value for Z I put in the config.g file, the clearance always ends up too small, and Z+0.3 always sets the gap right. It's as if whatever I put in the config.g file is being ignored and it's still using an old value from somewhere.

    My setup:
    Duet 0.6 running 1.19.2 firmware
    V1.2 mini height sensor board
    I do use bed mapping.

    The process I followed (from the Mini height sensor board web page):
    1. Heat the bed and hot-end to working temperature.
    2. Home X and Y, then move the carriage to the centre of the bed.
    3. Lower the head until the nozzle just grips a sheet of thin paper.
    4. Send G92 Z0
    5. Raise the head 5mm and remove the paper.
    6. Send G30 S-1
    7. Read the value for Z in web page, or from M114 (I get 0.787).
    8. Put the value into the M32 line of config.g (G31 P500 X0 Y0 Z0.787 ; Set threshold and offsets)
    9. Save config.g and accept the Duet reset.
    10. Heat the bed and nozzle again, home everything, and retest.

    This is all very frustrating, as this setup has been working happily for many months. However I do seem to have problems every time I try to set the nozzle height… Am I missing a step here? Am I doing something wrong?


  • administrators

    Do you have a config-override.g file, with another G31 command in it?



  • D'oh!

    Well called - there it is… hiding in plain sight.

    Call I just delete that from config-override.g?

    DON'T PANIC - I've fixed it the proper way (set the parameter on the command line, then M500)



  • And now it works… many thanks! 🙂

    David - is it worth noting that gotcha in your IR sensor instructions? I'm sure I won't be the last to fall for that one.



  • In my case I while building up I forgot to tighten the bolt holding my crude jury-rig mount, only the wires were actually keeping the sensor in vertical position; I had some wild initial printing where I confused this for sensor/glass bed failure and was frantically microstepping during skirt printing to correct the initial level. I eventually noticed it was flapping about during moves.. 3 seconds with an allen key and I got to move on to genuine glass bed sensing issues :-S

    'Tighten everything down' is probably another candidate for a gotcha list..


 

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