I asked this question as a small question under an answer of another question (How bed leveling is achieved without table screws?), but have been asked to post this as a separate question to answer it with more detail conform SE policy.

One question with respect to automatic bed leveling (also known as ABL): If the bed is tilted and the auto leveling measured this and then the printer adjust the z axis over the position on the bed, will a x-y-point on the first layer be located exactly under the (in model) same x-y-point in a higher layer, or will it be shifted to? I mean, if the bed is 1 mm lower on one side over 10 cm then a top corner of a 10-cm-cube should be also 1 mm shifted, so that the cube still is real cubic and not sheared.


Using automatic bed leveling assists you in getting the print to stick better to the build platform as a result of the print head following the non-uniform geometry or tilt of the build plate.

In, e.g. Marlin Firmware, the bed level correction is fading out over a predefined distance, this is determined by the constant #define ENABLE_LEVELING_FADE_HEIGHT in the printer firmware Configuration.h file and the height can be set with M420 Z<height> (see here).

M420 S1  ; Enable compensation using current grid/mesh
M420 Z10 ; Gradually reduce compensation until Z=10

If Z equals zero, leveling compensation will be fully applied to all layers of the print object.

Yes, a cube will not be perfectly cubic, that is why even with auto bed leveling you need to provide a bed as level as possible, it only should correct for very small deviations.

When the print is smaller than the fade out height, you would indeed get a sheared print, if larger, then the top of the print would be level with respect to the reference plane (machine true; this is the level of the X-Y plane, basically the level of the hot end carriage). Note that that still can be skew if the printer is improperly calibrated (e.g. when using 2 Z steppers or misalignment of the height on either side).


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.