Hi,

I have installed auto bed level on 2 of my machines. I am running arduino 2560 / ramps 1.4 / marlin. I use a micro servo with very little backlash and my own bracket designs that are very stiff. The mechanics of my setup are very repeatable. I tested the ABL with an M48 command and my standard deviation is less then 0.01 for both machines. That means the micro switch and bracketry is stiff and predictable.

The problem lies with my z offset. I get the value by rough measurement, then attempt to print, and then I adjust my next print accordingly to get closer to the perfect 1st layer thickness. This process takes 3 or 4 tries before I nail down my first layer thickness and the correct z offset.

I then edit my firmware and upload it. The new z offset is in the machine, I see it on my LCD screen.

However, despite all this, the machines do not show a consistent Z offset after a few prints. The z offset changes, by a large amount, on the order of millimeters. I end up having to recalibrate the zoffset frequently. I even went to lengths and bought a dial gauge and made brackets to mount it to the machine head, just to ensure the bed is flat.

I took every precaution to ensure the printing is repeatable and quick. The ABL system does work, the Z axis rods are turning and attempting to compensate, but z offset is just a ghost that I am trying to chase.

Any advice is appreciated.

- D