Delta Tower X, Y and Z co-ordinates

[MCOChuck]

I have a 170mm print bed on the Kossel and the following works well for me (you can create these as custom buttons in Pronterface)

X Tower - G1 F8000 X-60 Y-42 Z10
Y Tower - G1 F8000 X60 Y-42 Z10
Z Tower - G1 F8000 X0 Y60 Z10
Center - G1 F8000 X0 Y0 Z10

This is a good tutorial on manually calibrating your printer using the M665 and M666 commands: https://www.youtube.com/watch?v=tDLbqLve128

But you'll need to disable auto leveling in the firmware first. IIRC I followed a YouTube video to do this.

You'll likely need to enable EEPROM in your firmware. If you're using Marlin, go to the Configuration.h file -> Additional Features section and uncomment the following lines:
#define EEPROM_SETTINGS
#define EEPROM_CHITCHAT

On to manually calibrating your delta! Basically, if I understand it correctly as I'm new to this as well, you need to compensate for the inaccuracy between each endstop and the print bed, and also to correct for concave and convex motion across the print surface (Delta Radius).
To compensate for each tower's endstop to print surface distance, set the z height to be a few MM above the print surface in the firmware or using the M665 command to allow room for X, Y and Z tower negative offset, which you will set using the M666 command and save it to the EEPROM using the M500 command. You can verify what is set in EEPROM using the M501 command and what is stored in RAM using a M503.

Once you have all the endstop offsets correct, you need to edit the Delta Radius to correct for concave or convex motion along the print surface. Delta Radius is calculated by the following: DELTA_SMOOTH_ROD_OFFSET (minus) DELTA_EFFECTOR_OFFSET (minus) DELTA_CARRIAGE_OFFSET
-If moving concave, the Delta Radius Number is too High
-If moving convex, the Delta Radius Number is too Low
However much it's off by, make a change about 5 times bigger to the Delta Radius (so if it's off by ~1mm then change the delta radius by ~5mm) then start again with the tower offsets and test center again. Do this over and over until you're ready to throw your printer out the window, or all the tower offsets are correct and you have flat motion across the print surface.

I'm by no means an expert but hope that helps!

Not to hijack this thread, but I'm following the procedure above and running into problems with the Z tower offset. I can edit the X and Y tower offset, save to EEPROM and see the change after homing. The Z tower does not change...I could edit the offset from Z-0.5 to Z-50.0 and it will just sit on the endstop after saving to EEPROM and issuing a G28.
Any help is appreciated!

Chuck