Setting up Z probe


  • administrators

    How high is the nozzle tip above the bed when the probe triggers? That is the value you need in your G31 Z parameter.



  • Solved the problem. The 0.1 value in G31 was too low. I raised it to 10 and calibration worked faultlessly and very quickly.

    Thank you so much for your replies - you must spend an awful lot of time answering these questions and it is really appreciated. This must be one of the best forums for speed of reply.



  • So, if I am getting this right, the value of Z in G31 is equal to the offset between the nozzle and the point of the probe.


  • administrators

    Yes, it's the height of the tip of the nozzle above the bed when the probe triggers.



  • I have run the calibration routine a number of times, just to check everything is working okay, but it does raise a question of whether any changes are made to the config.g. I cannot see any change in the delta radius, rod length, printable radius or homed height in the M665 in config.g

    Does this mean I have to run the calibration every time I print? If so, I will find this very tedious as I need to fit the probe before calibration and then remove it after.

    How can I see any changes that are made so I can place them into config.g?


  • administrators

    The parameters found by auto calibration are not saved to config.g but they remain in effect until you restart the Duet. If you run M500 after auto calibration then the new parameters are saved to config-override.g. You should normally have a M501 command near the end of your config.g file to invoke config-override.g.

    After initial calibration I suggest you run M665 and M666 with no parameters to see what the new values are, and manually put them into your M665 and M666 commands in config.g.



  • Thank you - extremely helpful. Getting to grips with the Duet and all the masses of information available is quite daunting but, already I am astounded at the improvement over the original BrainWave. Thanks for all your efforts, much appreciated.



  • I don't seem to have a config-override.g and M500 and M501 do nothing. Do I have to create config-override.g somehow?

    Putting the M665 and M666 values in manually was a doddle - thanks.


  • administrators

    When you send M500 config-override.g should be created and various lines automatically added to it.


  • administrators

    The recommended procedure is here:
    https://duet3d.com/wiki/Configuring_RepRapFirmware_for_a_Delta_printer#Updating_config.g
    Although as you have a manually fitted probe I would not run auto calibration before each print


  • administrators

    @Mike_F:

    I don't seem to have a config-override.g and M500 and M501 do nothing. Do I have to create config-override.g somehow?

    Which firmware version are you running?



  • I am running 1.17e. I found I had to power cycle the board before config-override would show up. All done now and the printer is running fine. However, I just tried to save the heightmap, out of interest, and it saved okay but using M375 to view the file I got the message: M375
    Error: Failed to load height map from file heightmap.csv: invalid grid

    Not hugely important but I would like to have seen the grid.


  • administrators

    There was a bug in 1.17 that prevented the height map being loaded if lines in it exceeded a certain length. It was to fixed in 1.18.



  • I eventually managed to load version 1.18 but I am still getting the; Error: Failed to load height map from file heightmap.csv: invalid grid error message. I have power cycled the printer quite a few times and web page reports the correct versions of firmware. What else can I try to see the heightmap? The heightmap.csv file cannot be read from the SD card when it is placed in the PC either.


  • administrators

    @Mike_F:

    The heightmap.csv file cannot be read from the SD card when it is placed in the PC either.

    That is why its not reading in the web interface. Maybe a new G29 to generate a new file to see if that sorts it.



  • I am doing a G32 S2 which should save the heightmap to a csv file. After doing the routine and issuing an M374 the file is saved and I get a report that the file has been saved. It is when I try to read it with an M375 that I get the Error: Failed to load height map from file heightmap.csv: invalid grid

    I have tried it many times since updating the firmware with the same result. I have verified that the heightmap.csv is on the SD card. Incidentally, a csv file should be able to be read from the PC and loaded into a spreadsheet but the PC cannot open the file either.


  • administrators

    G32 uses bed.g for bed levelling - the height map is produced by G29

    See

    https://duet3d.com/wiki/Using_mesh_bed_compensation



  • Okay, thanks for that. So where does G32 store the result?


  • administrators

    @Mike_F:

    Okay, thanks for that. So where does G32 store the result?

    In memory. So it's lost when you restart the firmware.



  • lol I thought I was the only one doing FSR like this 🙂


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