<p>I finally manage to setup the ABL on my Prusa.
I run G28 to home all axes (for z I use the same probe used for ABL). Then
I run G29 E ( I use E because otherwise for some reason I have not understood yet, Z does not lift during probings) probing 4 points on the corners of the bed.</p>

<p>finally I get the map of the bed:</p>

<pre><code>Bed Level Correction Matrix:
+0.999999 +0.000000 +0.001233
-0.000005 +0.999992 +0.003905
-0.001233 -0.003905 +0.999992
</code></pre>

<p>and after that, the print starts.
The first layer looks perfect however I have not seen Z moving a single step along the printing.</p>

<p>Any hint about what to check? Is the obtained map indicating that the bed is already too leveled to act on any compensation?</p>

<p><strong>UPDATE</strong>
I printed a 180 mm diamater cylinder and the Z axis is not compensating the 1mm difference from edge to edge of the bed.</p>

[{'answer_id': 3032, 'author': 'Tom van der Zanden', 'author_id': 26, 'author_profile': 'https://3dprinting.stackexchange.com/users/26', 'pm_score': 1, 'selected': False, 'text': "<p>I believe that the matrix is shown transposed from how it should be, but that doesn't affect the answer. The compensated Z position is derived from the original <code>(X,Y,Z)</code> position by multiplying the corresponding vector with that matrix. This means that the new Z position would be</p>\n\n<pre><code>Z' = 0.999992Z - 0.001233X - 0.003905Y\n</code></pre>\n\n<p>If you have a 200 x 200 printbed, a diagonal move from one corner to the other would correspond to a 1mm change in Z-height. This should be noticeable, but if perhaps you're printing something quite small you might not notice it.</p>\n\n<p>Though, if your first layer is perfect, I would see no reason to mess with it.</p>\n"}, {'answer_id': 3034, 'author': 'FeliceM', 'author_id': 4388, 'author_profile': 'https://3dprinting.stackexchange.com/users/4388', 'pm_score': 2, 'selected': False, 'text': '<p>I found the issue. As I mentioned in my question UPDATE, trying to print something that cover the full bed, the ABL was not working.\nThe issue was the Gcode I added after the G29.\nIn fact for some reason I added a G28 X0 after the G29 and that basically cancel the data acquired in the G29.\nI learned something new, do not use G28 after G29!</p>\n\n<p>Now it is working nicely.</p>\n'}]
['https://3dprinting.stackexchange.com/questions/3031', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/4388/']