Auto_Bed_Leveling: Enhanced G29 command

[Astek777]

Hey Roxy

Just wondered whether you could shed any light on a problem I'm having with auto levelling on a Lulzbot Taz 5 (Rambo 1.3). It's sooooo close to working!!

I built a small capacitive sensor circuit which I installed and replaced my old, static z endstop with. I then installed and configure the BeckDac firmware as recommend (from page 48ish).

I seem to be getting very accurate, repeatable results with the sensor, however, whenever I print the levelling seems too close towards the front-left (closest X0, Y0) and then, if anything, too high towards front-right. The Z-Axis is moving though, so it's obviously trying to compensate.

I do have a glass print bed, and there were suggestions the sensor might not be reading correctly, so I am no printing on a sheet on aluminium but results remain the same.

Here's the calibration piece I'm trying to print:

Test Print.jpg


My start code is:

G28 ; home all axes
G29 n5 ; auto level bed

If I run 'G28 ; G29 V4 T n5' I get this:

******* FIRST RUN ********
RECEIVED: Eqn coefficients: a: 0.01 b: -0.00 d: 0.89
RECEIVED:
RECEIVED: Bed Height Topography:
RECEIVED: --1.61390 --0.90640 --0.21327 +0.44360 +0.99610
RECEIVED: --1.32577 --0.66765 --0.06640 +0.48798 +0.97235
RECEIVED: --1.07202 --0.44702 +0.06423 +0.53923 +0.94985
RECEIVED: --0.85202 --0.27327 +0.18798 +0.61548 +0.99423
RECEIVED: --0.67702 --0.14577 +0.26923 +0.70360 +1.03673
RECEIVED:
RECEIVED: planeNormal x: -0.01 y: 0.00 z: 1.00
RECEIVED:
RECEIVED:
RECEIVED: Bed Level Correction Matrix:
RECEIVED: 0.999958 0.000000 0.009196
RECEIVED: 0.000020 0.999998 -0.002187
RECEIVED: -0.009196 0.002187 0.999955
RECEIVED: ok

******* SECOND RUN ********
RECEIVED: Eqn coefficients: a: 0.01 b: -0.00 d: 0.88
RECEIVED:
RECEIVED: Bed Height Topography:
RECEIVED: --1.61460 --0.90898 --0.22023 +0.44415 +1.00790
RECEIVED: --1.33210 --0.67273 --0.06773 +0.48540 +0.97602
RECEIVED: --1.07460 --0.45835 +0.06727 +0.54352 +0.95040
RECEIVED: --0.84960 --0.27273 +0.19102 +0.61477 +1.00227
RECEIVED: --0.67273 --0.14210 +0.27165 +0.70165 +1.03040
RECEIVED:
RECEIVED: planeNormal x: -0.01 y: 0.00 z: 1.00
RECEIVED:
RECEIVED:
RECEIVED: Bed Level Correction Matrix:
RECEIVED: 0.999958 0.000000 0.009216
RECEIVED: 0.000020 0.999998 -0.002196
RECEIVED: -0.009216 0.002196 0.999955
RECEIVED: ok


******* THIRD RUN ********
RECEIVED: Eqn coefficients: a: 0.01 b: -0.00 d: 0.88
RECEIVED:
RECEIVED: Bed Height Topography:
RECEIVED: --1.62077 --0.91577 --0.21203 +0.44672 +1.01423
RECEIVED: --1.33452 --0.67515 --0.06953 +0.48735 +0.97860
RECEIVED: --1.07515 --0.45390 +0.05860 +0.53860 +0.94423
RECEIVED: --0.85015 --0.27015 +0.18672 +0.60422 +1.00860
RECEIVED: --0.66453 --0.13703 +0.26860 +0.70047 +1.04172
RECEIVED:
RECEIVED: planeNormal x: -0.01 y: 0.00 z: 1.00
RECEIVED:
RECEIVED:
RECEIVED: Bed Level Correction Matrix:
RECEIVED: 0.999957 0.000000 0.009226
RECEIVED: 0.000020 0.999998 -0.002206
RECEIVED: -0.009226 0.002206 0.999955
RECEIVED: ok


I have the bed purposely quite uneven as I was struggling to tell if the Z-Axis was moving at all to begin with.

I've attached a couple of config files in case they help at all.

Final thought on probe offsets, I believe these are correct. Probe is directly in front of extruder on X axis (0), is 30mm in front of extruder in Y axis (-30), and the gap between the extruder and bed is 2mm which Z is homed (-2).

Any thoughts or recommendations gratefully received! Thanks!!

PS. I've just taken some manual readings from a matching 9 points around the print bed after performing a G28 to home. These are the results which seem to match nicely with what the sensor is saying (+- 0.1).

Y / X | 30 | 147 | 262
------------------------------------
285 | -1.7 | -0.2 | +0.8

170 | -1.0 | 0 | +0.9

55 | -0.5 | +0.3 | +0.9