BLTouch probe failing after a cancelled print

Hi All,

(ADVi3++ v4.0.06 with BLTouch. Bed levelling prior to all prints with starting G-code added in Octoprint).

After cancelling a print over Octoprint, on the next print, when attempting an auto bed levelling, the probe fails and the nozzle hits the bed. To rectify this, I then manually level the bed, manually set z-height (using ADVi3++), then ABL again. This then works.

My assumption is that the z-height entered via ADVi3++ is overridden in the EEPROM by the ABL conducted by the starting G-code, but the z-height is not saved. So when the next ABL is initiated, the nozzle has no reference and crashes into the bed. The physical set up of the bed and nozzle has not changed, hence my assumption that it is a problem storing the levelling parameters.

Possible fixes would to move the ABL to the starting G-code entered by Cura, although I am not sure this will fix the error. I have limited knowledge of G-code, so its hard to determine why this is occuring.

Thanks for any advice !

It is unusual to set starting G-Code in OctoPrint. Why not, but I have not tested such configuration.

What does it means exactly? Can you describe it very precisely? First, which BLTouch do you have? Does it turn red, flashing, …?

No, unless you set it explicitly in the starting g-code. As you have not provided it, hard to say.

No, as soon at the BLTouch detects the bed, it stops the z-axis.

Thanks Sebastian, I believe that I fixed my problem now.

Can you explain how? Can be useful for other people.

Hi Sebastian,

My issues were all created by the mechanical set up of my BLTouch and printer. Firstly, the X-axis guide rods weren’t level. Second, since I am using an adjustable BLTouch Mount, the mount had slid up. When I checked it with my BLTouch calibration piece, it was a few millimetres above the 8-8.5 mm range. I have since marked the position of the BLTouch on the adjustable slide for reference as an easy visual check.

Golden Rule for BLTouch : If ever your nozzle touches the bed during ABL, check the physical mounting of the sensor.

Regards
Ian