2025 InMoov Two Servo Linear Drive Neck with Optical End Stops

Simplified design with enhanced positioning and tighter linkages over my previous design.

I started with the original InMoov neck Gael Langevin www.Inmoov.fr designed which only had flexion/extension and left and right rotation.
Then I changed over to Bob Houston's articulated neck here: https://www.thingiverse.com/thing:861146
After a series of mods and patches I changed over to Drupp's Parloma style neck here: https://www.thingiverse.com/thing:2059967
Still not satified with the movement control I decided to design a linear drive similar to that I created (https://www.thingiverse.com/thing:3743426) as a mod to Bob Houston's Articulating Stomach here: https://www.thingiverse.com/thing:1409964

The Drupp files are needed to make modifications to the InMoov torso so it can receive the linear drive cube. Drupp's Parloma Neck fits in this same space. HomPlateBackLeft and Right needed a wee bit of trimming after install to maintain the 80mm width of the rear entry.

Printing & Assembly Hints:

You will need four of these optical end stops: https://www.amazon.com/dp/B07PMW2QMT?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1
The right upper stop gets its mounting ear sliced off with a Dremel so it won't protrude.

I've include an Arduino test script Linear_Neck_Test.ino so you can see how to get it moving.

Imagine these parts in a stack:
Drupp_Neck_Hinge - the head mounts on this.
Neck_U_Joint_Base is secured in above with a 5/16" or 8mm bolt.
Neck_U_Joint_Coupling assembles to the Base
use the Neck_U_Joint_Star and print four Neck_U_Joint_Pins
Neck_Coupling - Print two and glue and press fit them together
Then glue that to the Neck_U_Joint_Coupling
Neck_Servo_Lid receives the entire neck & head assembly above. Glue it in place.
Route all the cranial wires down through the center holes & through the body of the universal joint star.

Now we'll start at the bottom and work our way back up to assemble the drive cube:
Print Neck_Servo_Base as the foundation.

I purchased two continuous rotation servos from Amazon for the drive system: https://www.amazon.com/dp/B01HSX1IDE?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1&th=1

Print two Neck_Servo_Lead_Screw The file contains a top and bottom half that interlock. The side with the central column gets pressed onto a 100mm x M8 x 2mm Pitch Lead Screw. Make sure the central column is facing away from the lead screw. The side with the two little pins mounts to the servo disc with two very small self tapping screws. Now the two halves may be pressed together.

Neck_Servo_Caps attach with 3mm machine screws and will act as guides and supports for the two Neck_Lead_Screw_Drives.

Print the Neck_Lead_Screw_Drives. Press an M8 Lead Screw nut into each, aligning the holes. Use four M3 x 10mm screws to secure each in place.

Thread each Neck_Lead_Screw_Drive onto its respective lead screw with the recessed holes on the side facing out. Those will secure the push rods to the Neck_U_Joint_Base, and the Neck_Pot_Rack_Gear. Spin the servos by hand to get the Neck_Lead_Screw_Drives all the way down.

Now the Neck_Pot_Rack_Gears may be secured to the Neck_Lead_Screw_Drives

Lastly, slip the Neck_Servo_Lid into place and secure with four M3 x 15mm machine screws.
It is possible to wait to glue the head assy into place so you may test and calibrate the cube first.

Install the head to the cube, and the whole business into the Torso with four M3 x 15mm machine screws in front and two small self tapping screws to hold Neck_Cube_Rear_Lower_Clip in place which mounts on the back of the cube and holds it in place.

Mount Neck_Rear_Cover on the bottom back of the skull. Drill a 2-3mm hole at the bottom of Neck_Rear_Cover.

To connect the Neck_Lead_Screw_Drives to the Neck_U_Joint_Base I used M3 x 50mm threaded rods (https://www.amazon.com/gp/product/B01LWPOXJO/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1) attached to RC ball joints (https://www.amazon.com/gp/product/B07SSZ1T46/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1)

Neck_Servo_Stabilizer caps the two 8mm threaded rods. Once in place I drilled two small holes in the Neck_U_Joint_Coupling and screwed in 2 3M x 10mm machine screws.