Help me understand Auto Leveling commands

The original Robo only understood G29, go do auto level. The two eeprom variables are probe offset and z offset. I do not understand why there is a need for two variables. I have tried modifying the probe offset and it does not have any effect. Is this only read on power up. Is it used at all? The trim adjustment is z offset.

The latest code has G36 which executes G35, find the probe offset followed by a G29. How can G35 make use of probe offset when If I manually modify probe offset it has no effect. Does G35 which uses the M851 command store the probe offset locally or in the eeprom? Does it load the eeprom then load from eeprom?

 

As you can see I am using the Bi Linear. I level with dial gauge at each corner, but the weight of the print head does cause some error across the bed in addition to the natural distortion of whatever surface I am using. I do not run the M420 command and everything plays. I am using Marlin 1.8.9. In my initial Gcode commands the first is to set the bed temperature and wait until it reaches temperature, so that the auto level is done on the same temperature I am going to print at. I let it go through a 5x5 matrix to allow the bed to arrive at full temp.

I am playing with the early model R2 and decided to dedicate it to PETG. I discovered that I could not get it to complete a print. I pulled out the print head and the filament was all distorted. I realized that the fan could not keep the heatsink cool enough with a 245C print temp. I put in an E3D wade print head with a MK8 hardened steel nozzle. The fan is a double ball bearing 30mm high output that snaps onto the heatsink and keeps it cool. My print has not yet finished ( a 12 hour print ) but the quality of what is there is so much better, finish and detail. So far Garolite with hairspray running at 80C is giving me the best bed attachment I will not know if it is good enough (no curling) until it is finished. I will spend a few days getting it all working (hopefully) and then do a write up..

Got 90% through then got an offset. I am now putting a dual gear drive because the PETG is soft and does not play well with the single gear.drive. Will get back.

 

Once a put a dual gear extruder in conjunction with an E3D using a larger more efficient fan I was able to print with PETG. Garolite works with parts that are not too solid like the Z axis stepper support being printed.

I have reduced what is required so that anyone with a drill press and some cheap Chinese taps can make the parts. If anyone has interest I will post the STL for the top piece which directly replaces the top two pieces on the R2. I can also post instructions on how to make the other parts from standard parts.