How to use G29 on a Delta?

Good day members,

Still struggling with my very first printer build / calibration.

Please also refer to this thread:
[forums.reprap.org]

I downloaded the latest Marlin firmware, RC version from here:

[github.com]

Configured it properly, and now my delta printer does what I think a proper auto bed level calibration/probing sequence.

Here is what I did:

1. In pronterface, I home all axis
2. send G29
3. printer head probes the bed at a bunch of seemingly logical / correct locations.
4. printer head moves to a slightly random location, then stops.
5. in pronterface, it spits out a bunch of coordinates:

G29 Auto Bed Leveling
33.51 33.61 33.44 33.27 29.52 32.28 39.42
30.15 31.49 31.46 31.78 31.29 36.24 41.19
29.12 29.30 29.48 30.29 33.06 35.06 37.06
28.10 28.55 29.00 29.73 32.59 33.00 28.57
27.25 29.89 32.53 20.20 25.19 30.19 35.18
26.40 -1.71 4.30 14.83 23.47 31.71 39.94
-35.94 -33.30 -23.92 3.28 21.74 33.23 44.71

6. seemingly nothing happends after that.

What do I do next? what is actually done in the back ground? I assume these are the z height of all the points probed? Why are there negative numbers?

I lowered the print head to z2, then did some pure x / y moves, and found that the print head is closer to the bed at center, and slightly further at edge (about 1.5mm).
This tells me that my delta radius is still off (too high), and G29 probably didn't adjust anything in the back ground to compensate, or maybe it did something, but I can't tell.

I can tweak the delta radius, but I would like to know how to use the G29 properly and correctly if possible. I was reading somewhere that I need to use some M codes
to make it remember certain things, for the G29 to take effect?

So confused right now.....

Thanks for your help in advance guys.

Kind regards,

Gordon

G29 is for bed leveling to make sure it can print flat on the bed.

Calibrating is so the effector can move flat across the bed and not convax or concave (higher in the center lower on the edges vise verus).

You dont do anything with the g29 info, it is loaded into ram and the printer use this information when it starts printing.

I'd suggest some type of z probe and an autocalibration firmware. I use Rich Cattell's marlin.

Once done just add g28,then g29 to your start G code (I also add a heat extruder without waiting and heat to just below the temperature at which my filament begins to ooze to save time, it heats whilst it does the auto level.)