I am trying to add auto bed leveling to my Prusa i3. When I run G28 my printer hits the X and Y end stops properly, then it assumes X=25, Y=99 position on the bed and performs Z homing, after which it stays there. The problem is when I run G29 then it starts following the grid points from this position and tries to go out of bed.

My settings for the grid are:


And travel limits are set to this:

#define X_MAX_POS 150
#define X_MIN_POS 0
#define Y_MAX_POS 150
#define Y_MIN_POS 0
#define Z_MAX_POS 220
#define Z_MIN_POS 0

I guess this might be relevant too:



  • $\begingroup$ What should be added to your question is the offset position of the sensor to determine the correct sensor bounds (see e.g. How to set Z-probe boundary limits in firmware when using automatic bed leveling?). Note that the presented code is somewhat dated w.r.t. current Marlin configuration, but, if correctly inserted, the printer homes in the middle of the bed dimensions. $\endgroup$
    – 0scar
    Jul 24, 2019 at 10:06

1 Answer 1


I don't know how your firmware load handles G29 ,but here's a guess, based on information at the reprap wiki . Try using FBLR to force the travel limits.


P Set the size of the grid that will be probed (P x P points). Not supported by non-linear delta printer bed leveling. Example: G29 P4 S Set the XY travel speed between probe points (in units/min)
D Dry-Run mode. Just evaluate the bed Topology - Don't apply or clean the rotation Matrix. Useful to check the topology after a first run of G29.
V Set the verbose level (0-4). Example: G29 V3
T Generate a Bed Topology Report. Example: G29 P5 T for a detailed report. This is useful for manual bed leveling and finding flaws in the bed (to assist with part placement). Not supported by non-linear delta printer bed leveling.
F Set the Front limit of the probing grid
B Set the Back limit of the probing grid.
L Set the Left limit of the probing grid
R Set the Right limit of the probing grid


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