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Auto-calibration is a firmware feature that will automatically calculate the parameters required for accurate printing by probing the bed at thirteen locations. However, there is a little prep work to setup the printer to be able to auto-calibrate wthout crashing the hot end into the bed.

The config.g file provided by UltiBots has reasonable initial values but we're going to add an extra margin of safety during commissioning. Click the Settings button and then the System Editor tab. Click the green (pencil) Edit button next to the config.g file.

The M558 command sets up the probing parameters. You'll find the M558 command near the bottom of the file. The H (dive height) parameter tells the printer to start probing the specified distance (in mm) above the bed. Set it to H50 and click the Save Changes button to save the file.

Even though the default Z height is in the ballpark (M665 H parameter), it could be off by 10-15mm higher or lower. Setting the M558 H50 gives the printer a little margin for safety by starting probing 50mm above where it thnks the bed surface is.

Reset the Duet when presented the option after saving the config.g file. If you don't get the option to reset, you will have to reset manually by entering the command M999 in the Send G-code... field at the top of the window.

Click the G-Code Console button and enter M665 in the field and press ENTER. The second screen capture shows the expected output, verify the homed height value - it should be 445.00mm.

Now enter M558 and press ENTER. The third screen capture shows the expected dive height you set above is correctly set to 50.0mm.

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