Auto Bed Leveling not level

I am running KimbraMarlin Dev and am experiencing a .06mm slope from the front of a skirt around a 30mm x30mm test cube to the back.

My X-min and Y-min are the front left corner of the hotbed. I see ABL actively moving the Z axis while printing. If I put a feeler gauge under the probe in the front right corner while running a G29 V4 the output shows the front right corner being different. I probe 16 points on the bed after homing X, Y and Z in the front right corner.

Does it make a difference WHERE Z is homed before the G29?

My printer is a modified Prusa i3 using Openbuilds V-Slot extrusions, 8mm Acme rods for the Z axis with anti-backlash nuts, Ramps 1.4 and a .5" Mic6 hotbed.

KimbraMarlin is too far diverged from the real Marlin. Is there a reason you aren't running RC-3 (Release Candidate 3) ????

You sure your bed doesn't have a dip or a lump in it? ie its not flat

As the ABL just take the average of the probed positions and says this is a flat plane
If one or two of the probed points is very low or high... it can get it wrong.

Do you have glass on your heated bed? (for flatness)

Edited 1 time(s). Last edit at 02/17/2016 09:41PM by Dust.

My hot bed is a 1/2" thick MIC6 aluminum plate, very flat and I am only probing 4 points (outer corners)

I seem to have better luck with Kimbra Marlin. Maybe I will try the RC3, is there a config utility like KimbraMarlin has?

The website thinks I am an automated bot!

Edited 1 time(s). Last edit at 02/19/2016 03:59PM by randyf1965.

Made a little head way on resolving this issue.

I changed my G28 from the X Y home position which had the proximity detector partially off the bed to the spot for the first G29 bed leveling location. Bed leveling is still off but not as bad as before. I also contacted Openbuilds regarding one of the anti-backlash nut they sent me, one is tight on the acme rod. I tried swapping them but it is tight on either rod the first step seems to me sticking slightly when moving up.

I also soldered up a y cable to wire my steppers in series, seem to sound better than running parallel.

If anyone is interested in the cable found a write up here:

[www.instructables.com]

Edited 1 time(s). Last edit at 02/21/2016 08:24PM by randyf1965.

Here is my latest G29 probing 4 points using a proximity detector on a 1/2" MIC6 aluminum bed.

I am printing some parts and will measure the skirt when it is done. The Z-Axis moves very slightly while printing.

Am I reading it correctly? The front left is low and the back right is high?

echo: G29 Auto Bed Leveling
echo: Bed X: 215.000 Y: 10.000 Z: -0.003
echo: Bed X: 42.000 Y: 10.000 Z: -0.110
echo: Bed X: 42.000 Y: 215.000 Z: -0.110
echo: Bed X: 215.000 Y: 215.000 Z: -0.170
echo: Eqn coefficients: a: 0.00013728 b: -0.00040854 d: -0.06980550
echo: Mean of sampled points: -0.09812500
echo: planeNormal x: -0.000137 y: 0.000409 z: 1.000000
echo: Bed Height Topography:
echo: +-----------+
echo: |...Back....|
echo: |Left..Right|
echo: |...Front...|
echo: +-----------+
echo: -0.01188 -0.07188
echo: -0.01188 +0.09562

echo: Corrected Bed Height vs. Bed Topology:
echo: +0.00168 -0.05832
echo: +0.00168 +0.10918

echo: Bed Level Correction Matrix:
echo: +1.000000 +0.000000 +0.000137
echo: +0.000000 +1.000000 -0.000409
echo: -0.000137 +0.000409 +1.000000