Auto_Bed_Leveling: Enhanced G29 command

[Roxy]

Yes, those numbers look OK. The problem is some where else. Let's do a G29 T V4 n5 and see what the bed's topology looks like.

[Bob]

I see my bed isn't very level.

ENDING:G29 n5 T V4
Roxy's Enhanced G29 Auto_Bed_Leveling Code V1.81:
Full support at http://3dprintboard.com
Bed x: 2.00 y: 1.00 z: 11.53
Bed x: 45.00 y: 1.00 z: 13.46
Bed x: 88.00 y: 1.00 z: 14.08
Bed x: 131.00 y: 1.00 z: 14.63
Bed x: 174.00 y: 1.00 z: 15.05
Bed x: 2.00 y: 37.00 z: 12.93
Bed x: 45.00 y: 37.00 z: 13.51
Bed x: 88.00 y: 37.00 z: 14.00
Bed x: 131.00 y: 37.00 z: 14.51
Bed x: 174.00 y: 37.00 z: 14.87
Bed x: 2.00 y: 73.00 z: 13.04Bed x: 45.00 y: 73.00 z: 13.54
Bed x: 88.00 y: 73.00 z: 13.96
Bed x: 131.00 y: 73.00 z: 14.38
Bed x: 174.00 y: 73.00 z: 14.67
Bed x: 2.00 y: 109.00 z: 13.08
Bed x: 45.00 y: 109.00 z: 13.52
Bed x: 88.00 y: 109.00 z: 13.84
Bed x: 131.00 y: 109.00 z: 14.16
Bed x: 174.00 y: 109.00 z: 14.36
Bed x: 2.00 y: 145.00 z: 13.06
Bed x: 45.00 y: 145.00 z: 13.38
Bed x: 88.00 y: 145.00 z: 13.63
Bed x: 131.00 y: 145.00 z: 13.85
Bed x: 174.00 y: 145.00 z: 13.96
Eqn coefficients: a: 0.01 b: -0.00 d: 12.98
Mean of sampled points: 13.800358

Bed Height Topography:
--0.73591 --0.41814 --0.16702 +0.04631 +0.15964
--0.71814 --0.27814 +0.04186 +0.36409 +0.55742
--0.75591 --0.25591 +0.15520 +0.57742 +0.86853
--0.87369 --0.29369 +0.19742 +0.70631 +1.07075
--2.26925 --0.33591 +0.27964 +0.82631 +1.25075

planeNormal x: -0.01 y: 0.00 z: 1.00

Bed Level Correction Matrix:
0.999945 0.000000 0.010521
0.000015 0.999999 -0.001429
-0.010521 0.001430 0.999944
echo:endstops hit: Y:0.00 Z:13.96

[Bob]

Sorry for the delay in answers. I run a home business, machining, and I have jobs to complete. I'll try to do better tomorrow.
BTW, I changed from 3 point leveling to 4.

[Roxy]

I see my bed isn't very level.

Bed Height Topography:
--0.73591 --0.41814 --0.16702 +0.04631 +0.15964
--0.71814 --0.27814 +0.04186 +0.36409 +0.55742
--0.75591 --0.25591 +0.15520 +0.57742 +0.86853
--0.87369 --0.29369 +0.19742 +0.70631 +1.07075
--2.26925 --0.33591 +0.27964 +0.82631 +1.25075

Yes, your bed is very not level. The Auto Bed Leveling can still print on that but as you move too far from the center the error starts to compound. It should be worth your time to get that much more level. And then if you re-run the same G29 as above we can check if your bed is flat or if it has high and low sports that aggravate the problem.

[AlexD]

Yesterday i rebuilt my bed system, its much more robust & rigid now. The first print i tried went very well. im going to try and get it dialed in real nice now. Thanks for the help, i will keep up to date on the autolevel progress.

[Bob]

Apparently I don't understand the topology map or I have something else really wrong.

In the map above I read that the back left, -0.73591, is low and the right front, 1.25075 is high. Is that a correct interpretation?

[Roxy]

Apparently I don't understand the topology map or I have something else really wrong.

In the map above I read that the back left, -0.73591, is low and the right front, 1.25075 is high. Is that a correct interpretation?

Yes, but that assumes you have the orientation set correctly. The default is to have the origin at the front left. But depending upon where you have the origin, you might have to change the #define's to get it aligned.

[Astek777]

Hi Roxy

if you have an inverted axis does this change the origin? I suspect not but I'm clutching at straws now.

Did some more tests. Using a 2x2 grid and mesh levelling seems to give good results. 2x2 grid with auto levelling scanning the same points gives me a low left (mainly front) and a slight high front right. For auto levelling I tried bringing these measures in my 20mm on each side, and then 50mm on each side but neither seemed to make any real difference.

I understand the basic difference between the two methods, but i don't really understand the difference between the two methods when using only a 2x2 grid...surely you've given both methods a perfect 4pt plane to use?

[Bob]

Yes, but that assumes you have the orientation set correctly. The default is to have the origin at the front left. But depending upon where you have the origin, you might have to change the #define's to get it aligned.

My origin, 0,0, is at the left front.

[Roxy]

Hi Roxy

if you have an inverted axis does this change the origin? I suspect not but I'm clutching at straws now.

It should not. But if you home towards minimum, that will be the origin. Unless you have set your bed dimensions to have negative numbers. Some people do that to put the origin at the center.

Did some more tests. Using a 2x2 grid and mesh levelling seems to give good results. 2x2 grid with auto levelling scanning the same points gives me a low left (mainly front) and a slight high front right. For auto levelling I tried bringing these measures in my 20mm on each side, and then 50mm on each side but neither seemed to make any real difference.

I understand the basic difference between the two methods, but i don't really understand the difference between the two methods when using only a 2x2 grid...surely you've given both methods a perfect 4pt plane to use?

I've never used the mesh leveling. I will when it can be used automatically.