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Z probe Issues Will not lock in - value

Posted by Mbardsley61 
Z probe Issues Will not lock in - value
October 17, 2019 04:06PM
Been playing with this, using marlin 1.1.9, attached is configuration.h file. My bltouch is actually -4.5mm on from my print head on the Z. This is a custom Core X/Y of my own design. every time i set M851, then M500, M501, then look at M503 it shows it right, but when I do a G1 F60 Z0, its still at true 0 not -4.5mm Any help would be appreciated. Thanks
open | download - Configuration.h (72.3 KB)
Re: Z probe Issues Will not lock in - value
October 22, 2019 03:42PM
Uh... I'm not understanding the problem. When you do G1 Z0 it should move the nozzle to the 0 position, i.e. just barely touching the bed.

That said, you really want your BLTouch trigger point to be when the nozzle is about 2mm above true 0 to ensure that when the pin is retracted it won't hit the bed when the nozzle goes to true 0.

Note that the actual position of the BLTouch body is irrelevant except with respect to how it alters the trigger point. The trigger point is what matters when setting Z offset.

Assuming you're using the BLTouch for homing:

  • Use "M851 Z0" to reset the Z offset.
  • Home the printer. At this point, the nozzle should end up around 2-2.5mm above the bed. If not, adjust the position of the BLTouch until it does. Your LCD should show Z=0 at this point.
  • Execute "M121" to disable hardware endstops, and "M211 S0" to disable software endstops.
  • Jog the Z axis down with your LCD until the nozzle just grabs a piece of paper. The LCD should show Z as a negative number, for example Z=-2.1
  • Run "M851 Zwhatever you measured" - for the example above use "M851 Z-2.1"
  • Home the printer again. The nozzle should end up around 2mm above the bed (same as before) but the Z on the LCD should read the negative of whatever you set for M851 (for example Z=2.1)
  • Execute "G0 Z0" and the nozzle should just grab a piece of paper and the LCD should show Z=0
  • Save the value with M500, and copy it into your Configuration.h.

Edited 2 time(s). Last edit at 10/23/2019 03:07PM by MMcLure.
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