<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.
The issue was the Gcode I added after the G29.
In fact for some reason I added a G28 X0 after the G29 and that basically cancel the data acquired in the G29.
I learned something new, do not use G28 after G29!</p>

<p>Now it is working nicely.</p>

CC BY-SA 3.0
2016-11-10T10:54:57.707Z
2016-11-10T10:54:57.707Z
FeliceM
<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>

<pre><code>Z' = 0.999992Z - 0.001233X - 0.003905Y
</code></pre>

<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>

<p>Though, if your first layer is perfect, I would see no reason to mess with it.</p>

CC BY-SA 3.0
2016-11-10T08:32:28.237Z
Agree with you about "don't fix what is fine" but if I installed the ABL is to have it working. I tried printing a 180mm diameter  cylinder 2 mm thickness. Since there is 1 mm change from corner to corner on Z, the ABL should have compensated. Nothing is happening. I do not see the Z working on the same layer from one edge to the opposite.
FeliceM
CC BY-SA 3.0
2016-11-09T19:59:04.193Z
2016-11-09T19:59:04.193Z
Tom van der Zanden
<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>

CC BY-SA 3.0
2016-11-09T16:42:59.673Z
If it ain't broke, why fix it?
Tom van der Zanden
CC BY-SA 3.0
2016-11-09T19:55:22.640Z
@TomvanderZanden, Lol....are you saying that is too leveled to call for Z compensation?
FeliceM
<marlin><z-probe>
Autobed leveling doesn't compensate
FeliceM
# Autobed leveling doesn't compensate

(Asked by: username_0 on 2016-11-09)

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.

finally I get the map of the bed:

```
Bed Level Correction Matrix:
+0.999999 +0.000000 +0.001233
-0.000005 +0.999992 +0.003905
-0.001233 -0.003905 +0.999992

```

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

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

**UPDATE**
I printed a 180 mm diamater cylinder and the Z axis is not compensating the 1mm difference from edge to edge of the bed.

**Tags:** marlin, z-probe

> **Comments:**
> **username_1**: If it ain't broke, why fix it?  
> **username_0**: @username_1, Lol....are you saying that is too leveled to call for Z compensation?  

---

## 2 answers

### Answer by username_0 on 2016-11-10. Score: 2

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.
The issue was the Gcode I added after the G29.
In fact for some reason I added a G28 X0 after the G29 and that basically cancel the data acquired in the G29.
I learned something new, do not use G28 after G29!

Now it is working nicely.


---

### Answer by username_1 on 2016-11-09. Score: 1

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 `(X,Y,Z)` position by multiplying the corresponding vector with that matrix. This means that the new Z position would be

```
Z' = 0.999992Z - 0.001233X - 0.003905Y

```

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.

Though, if your first layer is perfect, I would see no reason to mess with it.

> **Comments:**
> **username_0**: Agree with you about "don't fix what is fine" but if I installed the ABL is to have it working. I tried printing a 180mm diameter  cylinder 2 mm thickness. Since there is 1 mm change from corner to corner on Z, the ABL should have compensated. Nothing is happening. I do not see the Z working on the same layer from one edge to the opposite.  

---

