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G29 - Autoleveling for Tool Changing

Posted by 3dprinting01 
G29 - Autoleveling for Tool Changing
June 14, 2018 04:45AM

I'm using Marlin on a custom FDM printer running on an MKS 1.4 board, slicing with Simplify 3d.

The printer has 3 different heads, so I can change between materials/nozzle sizes.

The tools have different z-offsets, this is down to different designs for each head (one has direct drive for flexible filaments, the others have bowdens).

The only way I found to set the z-offset is to add a couple of lines in the toolchange script after picking up the tool as below (yer I know 36mm is alot of offset, but it works!):

; Set z Offset
{IF NEWTOOL=0}G1 Z36.1 F5000 ;
{IF NEWTOOL=0}G92 Z0 ; set as Z0

The problem I run into is with the G29 bed leveling command. Everything works fine until I add in the couple of lines above, when I presume the fw thinks 'Well I know the actual bed is 36mm away!' (even though the nozzle is right at the bed) and the leveling doesn't function during the print.

If I remove the 2 lines of script above (and don't allow it to actually pick up the tool to prevent a crash) the Z axis happily adjusts away during the print.

So my question is whether it's possible to override this? So having done a G29, picked up the tool and set the correct offset, the bed leveling treats this new offset as though the nozzle is at 0.

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