I recently bought and builded an Anycubic kossel plus, the build went very smooth till i came to test print some objects. The object i test printed had to be 20 x 20 x 10 mm but it came out as 18.25 x 18.25 x 11 mm. in the manual it says you have to adjust the DELTA_DIAGONAL_ROD with 1~3 steps at the time but i increased and decreased the value with 100 steps and the cube is still the same 18.25 x 18.25 x 11 mm.
i also have some problems with the convex printing, X100, Y0, Z10 it touches the plate almost, but when it is X0, Y0, Z0 there is like 1 centimetre gap between the nozzel and the plate.
thanks in advance 
For delta smooth rod, I recommend removing one of the rods and measuring it from center of each hole at the end. If its low in the center and high on the edges, you should decrease DELTA_PRINTABLE_RADIUS. I believe its supposed tobe around 116 for the plus version. The best way to adjust these is with the M665 command, then M500 to save. See G-code - RepRap and Delta 3D printer calibration with Marlin | Boim Systems
For adjust print objects dimensions: change DELTA_DIAGONAL_ROD, low value=big prints, high value=small prints For the height of prints objects: adjust motor step per unit, X Y Z to 80, for extruder E 96 For concave or convex bed plane: adjust DELTA_SMOOTH_ROD_OFFSET or DELTA_RADIUS value
I tried changing it in the arduino code then uploading it, but (i dont know why) when i change it nothing goes different, like the printer doenst care what i change at all
Probably you have set some values in EEPROM, send M502 (read parameters from firmware) and M500 (save parameters in EEPROM) If you change values in your firmware you need to make this procedure any times to see the effects
The M502 and M500 WORKED!!! It prints like a beast right now! Thanks so much, also the printer prints the good size, and it prints flat. Everything is fixed exept some minor imperfections but i think i can fix those myself! Thaaanks so much!!!
I’m happy for you! This printer will give you great satisfaction!
