Anet A6, Marlin 1.1.x, bed leveling with sensor probe I have an Anet A6, an SN04 sensor for the Z-axis, and Marlin 1.1.x software that has automatic bed leveling enabled.
My question is (looking at the image below): &quot;It seems my bed leveling is not working correctly. What can I do to improve it?&quot;

You can see several things below:

I tried to use glue to make the first layer adhere better.. works only for small prints;
the middle part of the print is being done quite okay;
the outer part are either too low or too high.

I used the following procedure to get my leveling &quot;right&quot;:
First I set the z-offset with the M851 command, followed by M500. Then I performed the bed leveling with G29 T, followed by M500. Then I started my print.
Maybe I need more grid points for my bed leveling, even though I have this interpolation method on. Or do I need to check the implementation of the bed leveling, maybe something is just plain wrong in the software.
What is your recommendation?
Current bed level status (M420 V)

Send: M420 V  
Recv: Bilinear Leveling Grid:  
Recv: &emsp;&emsp;&emsp;  0  &emsp; &emsp; 1 &emsp; &emsp;  2 &emsp; &emsp;  3 &emsp;  &emsp; 4 &emsp; &emsp;  5  
Recv:  0 +0.709 +0.609 +0.519 +0.456 +0.448 +0.404  
Recv:  1 +0.525 +0.440 +0.370 +0.325 +0.304 +0.298  
Recv:  2 +0.368 +0.282 +0.222 +0.177 +0.189 +0.182  
Recv:  3 +0.221 +0.152 +0.100 +0.055 +0.069 +0.082  
Recv:  4 +0.086 +0.020 -0.028 -0.060 -0.050 -0.020  
Recv:  5 -0.027 -0.093 -0.138 -0.187 -0.163 -0.146
Eventually it was a mixture of things that sort of solved this.

Setting the Z-offset a bit more tight helped some
Probing with more gridpoints helped
Instead of using glue, I used painterstape. Way easier to refresh and easier to take prints off. I wanted to try kapton tape, but painterstape was good enough for now.
Manually leveling the bed to a better position also helped.
(After edit) recalibrating my two z-axis motors.

In the end, I think my bed has become a bit curved over time. So a final solution would be to print on a glass bed, but that was not really an option when using the SN04 sensor.
I am moving now to a BLTouch sensor + glass bed to make everything perfect again.
EDIT: important note, I also put off bed heating. Since I am working with PLA, it was not really necessary. Doing this allowed me to use painterstape, otherwise it would 'fall off' eventually.
EDIT2: I think I have thought of a better explanation. I am using an Anet A6 and it might be because the x-axis was not parallel to the plate. Meaning that my two z-axis stepper motors were not calibrated properly.