Another Calibration issue Folgeltec kossel mini marlin 1.1.5

hi everyone,

so after a bit of time playing with a home built mendel90 i got offered a Fogletech kossel mini
(2020 extrusion, aluminum corners, ramps 1.4, reprap discount smart controller)

i have fixed a few build issues and upgraded firmware to marlin 1.1.5 (using the "stock" config for the kossel mini from marlin directory and modifying to suit)

i have adjusted the end stops so that when the nozzle is in front of each tower they read the same
tower A 10.5, tower B 10.5 and tower C 10.5.
the center is 0.
so as you can see the printer thinks its a long way out. i believe that is called a convex print surface.

from there I adjusted the "#define DELTA_RADIUS 120" to be correct
(if i tell it to move 80mm it moves 80 mm)
(also this didnt effect the convex problem)

but that is as far as i can get. From the reading i have done, next, i have to adjust the "#define DELTA_DIAGONAL_ROD 230"
I have adjusted this from 180-260 and it has NO affect on the distance between the nozzle and the print surface in front of the towers.
(they all still measure 10.5 and the center 0.0)

I have done a lot of reading, and the change from "delta_smooth_rod" (pre1.1.1) leaves a lot of instructions useless
this one i found very useful
[www.mindmeister.com]

What am i missing here?

Chris

here is a snip from the config.h, for the delta variables
// Print surface diameter/2 minus unreachable space (avoid collisions with vertical towers).
#define DELTA_PRINTABLE_RADIUS 110.0 // mm

// Center-to-center distance of the holes in the diagonal push rods.
// is actually 230mm
// tried down as low as 180 with no effect.
// tried up to 240 with no difference to 180.
#define DELTA_DIAGONAL_ROD 230 // mm CH WAS 215

// height from z=0 to home position
#define DELTA_HEIGHT 244 // get this value from auto calibrate

#define DELTA_ENDSTOP_ADJ { 0.0, 0.0, 0.0 } // get these from auto calibrate

// Horizontal distance bridged by diagonal push rods when effector is centered.
//(this is actually about 145. but it works at 120. ie 80mm is 80mm)
#define DELTA_RADIUS 120 // Get this value from auto calibrate

// Trim adjustments for individual towers
// tower angle corrections for X and Y tower / rotate XYZ so Z tower angle = 0
// measured in degrees anticlockwise looking from above the printer
#define DELTA_TOWER_ANGLE_TRIM { 0.0, 0.0, 0.0 } // get these values from auto calibrate

// delta radius and diagonal rod adjustments measured in mm
//#define DELTA_RADIUS_TRIM_TOWER { 0.0, 0.0, 0.0 }
//#define DELTA_DIAGONAL_ROD_TRIM_TOWER { 0.0, 0.0, 0.0 }



distance between the ball join on the effector and the center of hotend is 35mm
(but this does not seem to have an entry in the "delta setup" where the above parameters are found.)

Get your delta geometry values as accurate as you can, and fine tune with calibration G33. This should be fractions of a mm or something is wrong.

Do not forget to load them and save into EEPROM to take effect (M502 M500)