@dc42 @Wyvern guess the problem is solved: I just switched to a switch (ha) anycubic probe sitting right under the nozzle, and here is the result... which at least confirms the fairly good "trueness" of the frame (for which I ran out of any possible options):
Thanks once again for pointing me towards the right direction!! 
@wyvern yes agree w/ having a simple mechanical switch (at the time I got it it wasn't included... but anyways the only anycubic stuff left are the 2020 extrusions, rods and effector :)).
Just the tilt, is in any case unexplained to myself.
@dc42 said in Kossel linear plus: tuning a poor mesh grid:
Offset probes such as BLTouch are extremely sensitive to effector tilt. For example, if your BLTouch is offset from the nozzle by 25mm, then a chan
Yes, it is definitively still.
My probe is a BLTouch, and being a delta effector, it's forcibly Y-offseted from the nozzle by exactly 40mm: adding a picture just to show the effector setup:
@Veti I use 6 calibration factors (13pts), here is my bed.g: 0_1550510388221_bed.g
@dc42 The circular spirit level on top of the effector gives me of course the reference to the ground, but the positioning of the bubble is pretty centered and is consistent moving it across the bed. Given I placed it above the metal casing of the fans (40mm above the rod axes), the error should be even amplified, so should be ok...
That said, I’d expect that given that the glass bed is flat (measured with a precision square), the bed compensation should do the on-the fly corrections as the print is being executed, according to the poor mesh… instead it looks like it’s ineffective since it looks like the mesh just keeps the Zmax deviation (0.3mm) as the Z=0.
I've proven this to myself by manually jogging to Z=0, measuring -0.3mm of bed distance and then adding it to the M665 height along with disabling M501 in config.g, but keeping M375.
In lack of ideas, I even tried rotating the bed… but got roughly the same results, so one might say it could be the top frame extrusions on which the bed is directly laying (even though the whole frame is truly squared and measured with precision workshop tools), but again, if I put a flat surface on top of the frame extrusions, and given the bed is not being bent by any clamp (as it’s only firmly kept on the sides by plastic mounts), I'd expect the bed compensation should dynamically correct the print… or am I missing something?
Here is also my config-override.g, being loaded by M501 at the end of config.g:
0_1550511164818_config-override.g
Issue is I just can't get that perfect 1st layer... and it's driving me nuts 
Thanks for any help/suggestion.
@Veti thanks for that resource, really interesting article.
Not sure though it's a symmetry problem, as mentioned the whole printer is maniacally squared and leveled against the all metal CNCed corners & 2020 profiles... moreover, everything is assembled with proper chuncky T-nuts (not those useless square bolts).
Could it be perhaps be a slight rod/radius length difference (looking at the article you pointed out)?
Hello all,
I'm struggling in trying to fine tune my Kossel linear plus printer.
Prints are coming out fairly good, but I'm getting out this "not so good" heatmap, with a corner bent down 0.216mm:
The whole printer is maniacally squared and leveled against the all metal CNCed corners (even carriages & head are metal).
The levelling probe is an original BLTouch.
The bed is a 240x4mm borosilicate glass disk, directly laying on the 3 lower-top 2020 aluminum extrusions, so absolutely flat and therefore I cannot understand why I’m getting this convexplane... which is btw pretty much compatible with some warping of the prints in that "blu" area.
Can anyone suggest what can I possibly look after, as I totally ran out of options here? 
Thanks for any help!
@fcwilt good point, thank you!
You're right, especially at the beginning, when you're always hands-on with configs, it doesn't help scattering around with all the updating here and there, in place of a simple M500.
On the other side though, you learn a lot about what you're doing, which isn't bad 
Now that my delta is all fine tuned, I will start relying on this suggested practice of yours for any other further tweak I may need in the future.
Thanks
Gianni
@dc42 super, you nailed it again: I was "a bit off" with the delta radius.
Thank you very much!
@fcwilt thanks for pointing out raising the S parameter, definitively better option (was just using the auto-generated bed.g from the RepRap configurator).
But unfortunately raising to S6 (also tried S9) did not have any effect on the above result.
Regarding the M501 commented out in the config.g, it's simply because I prefer to have all values reported in the main config, rather than having an override file... but i new to Duet & RepRap, so might be doing something wrong: is it obbligatory to M500 & M501?
Gianni
I managed to fully configure my Kossel Plus, up to having Auto Delta calibration (with a fixed BLTouch) work perfectly.
I even succesfully printed some objects without issues.
I wanted to try mesh leveling, but I always get the following result after all the probes:
What could be the issue?
Including my config.g & bed.g:
1_1548548684464_config.g 0_1548548684463_bed.g
Thanks for any help!
@dc42, that's exactly what I was missing: endstop adjustments!
Auto-calibrating with a greater probe height in M558 (20 was enough in my case) allowed me to grab the resulting values to be fed into the M666 inside config.g.
Thank you very much for your prompt support!
Yes I did and it all worked, resulting in Z=1.9 correction in the G31 command in config.g, that is now:
G31 P25 X0 Y-40 Z1.9
So I decided to commit and proceeded with the Auto Delta Calibration, BUT here is what happens:
Luckily the emergency button is quick enough to stop the crash at its beginning…
What could be causing this?
Hi,
I have fully operational Anycubic Kossel Plus + BLTouch rig, that I just migrated from stock-Trigorilla to Duet 2 WiFi v1.04 (after a succesful goodbye print of the Duet mounts ;)).
Now, all the wiring should be ok, as all the tests I made so far have passed, EXCEPT ONE: when I start the Auto Delta Calibration, and test if it stops by manually triggering the BL Touch, it does not stop!
BLTouch is correctly wired as per what indicated here: https://duet3d.dozuki.com/Wiki/Connecting_a_Z_probe#BLTouch
I can command the BLT to do up, down, self test and reset, and I can see the Probe state change from 0 to 1000 by performing the tests in the doc.
Here is my config: 0_1548409538729_config.g
What could be wrong?
Many thanks for any help.