Cebulatron robot arm fourth axis

This actuator is fourth axis or first wrist joint of 6-axis robot arm. To drive I used one Nema 23 stepper motor, but it is possible to use two Nema 23 however it adds mass to the robot and load 2nd and 3rd axes. The FourthAxisBodyHalfNew has compatible mounting holes with the second axis (https://www.thingiverse.com/thing:5405129). The gear ratio is 1:6 (motor gear has 15 teeth and ring gear has 90 teeth). The hole in motor gear need to be drilled to press the gear on the motor shaft.

BOM:
6x M3x18 DIN 912 hexagon socket head cap screws (it might be necessary to shorten them a bit)
6x M3x25 DIN 912 hexagon socket head cap screws
6x M4x20 DIN 912 hexagon socket head cap screws
3x M5x30 DIN 912 hexagon socket head cap screws
4x M5x16 DIN 912 hexagon socket head cap screws for mounting motor (1x Nema23)
20x M4 nuts
2x 61810 Ball bearings
Nema 23 stepper motor
RAMPS 1.4 or another board to control the motor(s)