Removable Z-Probe Height and Bed Leveling

tcurdt

I've got a delta printer with a removable z-probe (that sits on the nozzle) and I am a little confused with the z-probe and autolevel topic. This is what I tried:

First I calibrated the endstops/towers:

G28

G131

M99 X0

M99 Y0

M99 Z0

G132 S1

< 23:16:49: Tower 1:28

< 23:16:49: Tower 2:47

< 23:16:49: Tower 3:0

Then I levelled the bed:

G32 S2

< 23:22:49: X:0.00 Y:0.00 Z:295.937 E:0.0000

< 23:22:56: Z-probe:49.79 X:-66.00 Y:-38.00

< 23:23:00: Z-probe:49.86 X:66.00 Y:-38.00

< 23:23:03: Z-probe:49.89 X:0.00 Y:66.00

< 23:23:04: plane: a = 0.0006 b = 0.0006 c = 49.8478

< 23:23:04: Transformation matrix: 1.000000 0.000000 -0.000568 -0.000000 1.000000 -0.000603 0.000568 0.000603 1.000000

< 23:23:04: CurrentZ:49.89 atZ:50.00

< 23:23:04: Z after rotation:50.00

< 23:23:04: Printer height:295.82

< 23:23:04: Info:Autoleveling enabled

< 23:23:05: X:-0.03 Y:65.97 Z:49.915 E:0.0000

< 23:23:05: Info:Autoleveling disabled

< 23:23:12: SelectExtruder:0

< 23:23:13: X:0.00 Y:0.00 Z:295.825 E:0.0000

< 23:23:13: Info:Autoleveling enabled

Now I would have thought that Z0 currently would be where the z-probe hits the bed. But it turns out that's not true. 

G0 Z40

lets the z-probe hit the bed, while

G0 Z34.8

Let's the nozzle hit the bed.

Now I am wondering if that's because the z-probe height is set to 40. So my guess is I now have to modify the z-probe height. But if I subtract the 34.8 from the current z-probe height at 40 and use the resulting 5.4, I am getting:

< 00:01:56: Error:z-probe triggered before starting probing.

I've read this document and it seems to suggest to do a similar thing

  ZHnew = ZHold + Z0 + Znew - Zold - ref_height

Unfortunately the text mentions Zstart and Zend but not Znew and Zold. (I guess that's worth fixing).

Some help would be much appreciated.

cheers,
Torsten