UBL Auto Leveling - setting to cover the bed

I am having difficulties to understand how to set up UBL to cover as much bed as possible.
I have not square bed 250x290, but my probe can reach all of it ( not as nozzle but close)
I understand that settings I am looking for is MESH_INSET and PROBING_MARGIN
Initially I had set to
MESH_INSET 1
PROBING_MARGIN 10

But that was failing on 57/100 points and causing printer to HALT.

With settings
MESH_INSET 30
PROBING_MARGIN 50
I have managed to complete G29 P1, but that does not cover whole bed, I know I can run G29 P3 which I do, but I want to cover as much as I can with a probe itself.

So how should I set it up, I was thinking something like:
MESH_INSET 0
PROBING_MARGIN 5

but I am not sure I understand it correctly.
I would really appreciate any help

As long as X_MIN_POS/Y_MIN_POS and X_BED_SIZE/Y_BED_SIZE as well as NOZZLE_TO_PROBE_OFFSET are set correctly, you should not need to use PROBING_MARGIN. PROBING_MARGIN is required only for probes that behave badly near the edge of the bed such as inductive or capacitive probes. A BLTouch should not require PROBING_MARGIN.

What you should ensure is that X_MIN_POS and Y_MIN_POS are set correctly such that when you move to 0,0 the nozzle is right over the front left corner of the bed. This may require X_MIN_POS and/or Y_MIN_POS to be negative. Also, if the nozzle can safely move past the right or back edge(s) of the bed, you can increase X_MAX_POS/Y_MAX_POS accordingly - this may allow the probe to reach more of the bed. For example, on my printer I have:

#define X_MIN_POS -20
#define Y_MIN_POS -21
#define Z_MIN_POS 0
#define X_MAX_POS X_BED_SIZE + 15
#define Y_MAX_POS Y_BED_SIZE + 5
#define Z_MAX_POS 260
...
#define NOZZLE_TO_PROBE_OFFSET { -29, 1, -1.10 }
...
#define PROBING_MARGIN 0
...
#define MESH_INSET 3

With these settings I can probe all of the bed except for the rightmost column (since that would require moving the nozzle to X=249 which is outside X_MAX_POS).
Note that being unable to probe the whole bed is not a problem with UBL - once you have run G29 P1 to probe the bed, you can fill in the un-probed points with reasonable values using G29 P3 before saving your mesh.
If PROBING_MARGIN is not 0, it will be impossible for UBL to probe the four edges of the bed and these will need to be filled in with G29 P3.

Awesome,

I will have a go, I currently have PROBIMG_MARGIN set to 0, and inset set to 5 , however I can only manager 91/100 points but pretty much on all edges.
But I also realised, that my X=0 is not actually on the edge of the bed, looks like nozzle can only reach X=+10mm of the bed physically, so I have to check real measurements and available points and update MIN_POS accordingly.
Thank you for that hint. Hopefully I will get it. And I am aware of G29 P3, it's just ... you know would be nice to cover as much as you can with probe

OK So I did my measurements and my current settings are:

// The size of the print bed
#define X_BED_SIZE 288
#define Y_BED_SIZE 250

// Travel limits (mm) after homing, corresponding to endstop positions.
#define X_MIN_POS 0
#define Y_MIN_POS 0
#define Z_MIN_POS 0
#define X_MAX_POS 299
#define Y_MAX_POS Y_BED_SIZE
#define Z_MAX_POS 285

#define MESH_INSET 3 
#define PROBING_MARGIN 0

But still it stops at 91/100 points. It goes to the corners, and G29 P3 does the job and all looks good.
But it just doesn't seem right that it can do 100 points.

first issue i see is that you have defined X_MAX_POS as 299 but your X_BED_SIZE is 288

I think 100 points is excessive I would suggest starting with 9 or 16 points than working your way up to a greater number

Edited 1 time(s). Last edit at 12/05/2020 12:22PM by bigfilsing.

Well I thought if I define higher X limit when probe can actually reach, which is bed size + probe offset so it's 299, but bed size ends at 288.
But that didn't seem to make a difference.
I successfully get 90 points so I might define it to that or something like that.

Also answering previous suggestions. Changing amount of points doesn't change anything, I've tried 49 points and it still doesn't get 49 points but 43/49.
I guess the calculation of points needs to be correct otherwise it doesn't matter how many points I think.

Quote
uneasy
Also answering previous suggestions. Changing amount of points doesn't change anything, I've tried 49 points and it still doesn't get 49 points but 43/49.
I guess the calculation of points needs to be correct otherwise it doesn't matter how many points I think.

Honestly i'm not sure if there is a limit to the max number of probe points but considering they are recorded as a compensation matrix/mesh you may be overloading the memory allocation.
As far as i know the points are plotted as a sub division of the bed dimensions minus the probe margin ( and accounting for the probe off set)

Its been a while since i played with ABL but id still recommend starting with say16 so its easy to visually monitor what's going on.

Are you then talking aboult ABL then ? Because I am talking about UBL.
There is safe limit of 15 grid which is 15x15 points. 10 is default (100) points

Quote
uneasy
Are you then talking aboult ABL then ? Because I am talking about UBL.
There is safe limit of 15 grid which is 15x15 points. 10 is default (100) points

Yes I'm talking ABL . but i dont think the bed definition & layout differs

If i remember correctly Chris Riley did a video a few months back on UBL That might be worth finding and watching

Edited 1 time(s). Last edit at 12/06/2020 09:58AM by bigfilsing.