Mesh Bed Compensation and Bed Leveling
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Hi Everyone,
I have a question about using these two functions. I have a CoreXY with 4 Z lead screws connected to 4 Z motors using a Precision Piezo Orion as the probe.
Currently what I do is home all axis, and then conduct auto bed leveling in 4 points doing three iterations. Below is an example of the results
2:13:47 PMLeadscrew adjustments made: 0.003 0.002 0.004 0.003, points used 4, deviation before 0.003 after 0.000
2:13:18 PMLeadscrew adjustments made: 0.004 0.001 0.001 0.001, points used 4, deviation before 0.003 after 0.000
2:12:50 PMG32
Leadscrew adjustments made: 0.180 0.181 0.175 0.170, points used 4, deviation before 0.176 after 0.000.As you can see, I have a light lean in the bed from side to side when the motors are depowered that seems to be sorted using the 4 z axis motors, which is excellent. It works as it should when I test the zero height in all the corners.
Now when I use mesh bed compensation and do a run, I get the below results
It shows that the 6mm tooling plate and print surface has some slight deviations. This may have been how I mounted the plate to the z carriage (having countersunk holes) maybe relieving internal stress in the plate. I guess that's what the mesh compensation is for however.
What I don't understand however is the 4 corners that the auto compensation levels, is now out of level by more than what the deviation was during the auto bed leveling. After the mesh leveling was done, I then ran an auto bed leveling again and got below:
3:02:20 PMLeadscrew adjustments made: 0.005 0.006 -0.004 -0.009, points used 4, deviation before 0.006 after 0.000
3:01:52 PMLeadscrew adjustments made: -0.007 0.001 -0.000 -0.001, points used 4, deviation before 0.005 after 0.000
3:01:24 PMG32
Leadscrew adjustments made: 0.002 0.006 0.008 0.006, points used 4, deviation before 0.006 after 0.000This seemed to show that it is pretty normal and still less than what is being measured in the mesh compensation. Maybe not as good a before. Is the difference between the two because it clears any height transformations before it does the mesh compensation? The reason for asking is I seem to have issues getting my first layer to stick consistently. I am using PrintBite+ which is awesome. Things stick really well to it, however sometimes some areas of the part do not stick as well as other areas of the part and I am wondering if the bed compensation has something to do with it.
Does anyone have any thoughts on this?
Kind Regards,
Sam -
I also ran a second mesh compensation after and it is very very close to the above one.
Kind Regards,
Sam -
Do the 4 points you use for bed levelling fall within the area covered by the mesh?
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I forgot to mention I also re home the z axis after the auto bed leveling before I run the mesh compensation.
Kind Regards,
Sam
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That does seem odd. Can you arrange it so that the 4 points that you use for bed levelling correspond exactly to points on the mesh?
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Hi @dc42
So I had a look at the actual maximum probing points for the mesh compensation and used them for the bed leveling.
Here was the probing for the auto leveling:
8:39:12 PMLeadscrew adjustments made: 0.001 -0.001 -0.000 -0.001, points used 4, deviation before 0.001 after 0.000
8:38:44 PMLeadscrew adjustments made: -0.003 0.003 0.001 -0.001, points used 4, deviation before 0.004 after 0.000
8:38:16 PMLeadscrew adjustments made: 0.156 0.148 0.154 0.151, points used 4, deviation before 0.153 after 0.000Here is the mesh height map:
This was the results from doing auto leveling right after:
9:14:34 PMLeadscrew adjustments made: -0.000 0.004 -0.002 -0.002, points used 4, deviation before 0.003 after 0.000
9:14:07 PMLeadscrew adjustments made: -0.001 0.002 0.008 0.003, points used 4, deviation before 0.005 after 0.000
9:13:39 PMG32
Leadscrew adjustments made: 0.006 0.019 0.031 0.014, points used 4, deviation before 0.022 after 0.000I guess the points do line up other than maybe the second that was 0.01mm out. I am guessing some of the issues I am having could be attributed to the fact that there would be a compounding error over 342 x2 z movements as it probes every point twice?
Kind Regards,
Sam -
Another quick question, do you have to specify a taper at all in the .config or does it default if you do not specify the M376 code? I have not had it in my config file.
Kind Regards,
Sam -
If you probe repeatedly in the high-X high-y region (where the error appears to be greatest) using G30 S-1, do you get a consistent trigger height reading?
The default is that bed compensation is not tapered.
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Hi @dc42
Thanks for that. I will give it a go.So by not tapering, does that have an effect on the compensation? Or will it compensate over the entire height of the print?
Regards,
Sam -
@samlogan87 said in Mesh Bed Compensation and Bed Leveling:
Or will it compensate over the entire height of the print?
Exactly.
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Hi @Phaedrux
Thanks for clarifying that. I just seem to have a few issues with consistency between mesh compensation results and auto leveling that I think is causing issues with my first layer being inaccurate.
Kind Regards,
Sam -
For almost any case like this, my first go-to for an explanation would be a machinist's straight edge. 0.1mm deviation over a couple hundred mm is practically impossible to see, but that straightedge should tell the real story. If you are getting incorrect reporting from the sensor, the first step is to determine if your sensor is wrong.
If your sensor is wrong, then the idea is to determine what rules (And there will be some) that determine HOW it is wrong. Sometimes certain portions of the bed have more compliance than others, particularly when your bed is spring mounted. Sometimes there is a sag or bow in axis rails, and though the bed isn't bent, the probe is correct. this is one of the things that a mesh probe can help correct for.
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I did one more run last night of the mesh leveling and I want to do another one again tonight to confirm, but some of it could be a slightly bent Y axis (That is my moving carriage axis). I am still getting inconsistency in the mesh leveling which I am not overly sure why, hence the post.
Kind Regards,
Sam
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Well, I did another run and it is not a bent y axis. When I set it up, I had a few good nozzle digs into the bed and I am wondering whether somehow in doing so, it managed to put a slight bow in the center of the bed.
@dc42 When I run G30 S-1 with the piezo probe, it does not lift after probing and progressively digs harder into the bed. Not sure what I need to change to stop this. Even so at X 340 Y360 according to the mesh height map, the z value should be .197mm. When I probe it is 0.02mm.
Kind Regards,
Sam -
You need to raise the head by 5mm between each pair of G30 S-1 commands.
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