This project is a fully 3D printable, actuated skull which plays a series of different "animations" when triggered by motion on a PIR sensor.

The goal of this project was to make an accessible design using commonly available Arduino parts and a minimal amount of soldering. The 3D designs are all quite simple and should be easily printed on any level of 3D printer. This is a great learning project as it introduces a basic geared system and has a clean code base which can easily be expanded to produce more custom designed "animations".

So if you want to build a little animatronic, learn a bit about gears or Arduino coding, or if you just want to create a spooky decoration to scare visitors then this is the project for you!

FULL BUILD INSTRUCTIONS CAN BE FOUND HERE ON INSTRUCTABLES

The first step is to 3D print all the required components required for this build as are listed in the section above. All the parts not listed as optional are required for the main body of the skull, the two optional components are for housing the PIR sensor if you need a mounting solution.

You can print your skull in any colours you desire, but I chose to go classic and use white for the Skull and Jaw parts, and then Black for everything else. I used a matt PLA for the white parts to give a more realistic "bone" finish, however this will make these parts weaker than using a standard PLA+ with a glossy finish. I used a standard black PLA+ for all the other parts.

I printed all these parts at a fairly high speed and still got decent quality results, but if you know your printer is less accurate it might be worth reducing the speed to make sure push fits/screw holes are as accurate as possible.

The following are simple small prints which can just be printed without supports:

• Servo Bracket (print with the large flat surface to the build plate so the screw hole legs point up)
• Servo Gear (print in the orientation provided)
• Left Eye Cover (print in the orientation provided)
• Right Eve Cover (print in the orientation provided)
• Nose Cover (print in the orientation provided)
• Back Cover (print in the flipped orientation so the screw hole chamfers face up)
• (Optional) PIR Case Front (print in the orientation provided)
• (Optional) PIR Case Back (Tack) (print in the flipped orientation so the screw hole legs point up)

The two main parts of the skull require supports to get the best print results:

• Skull - Orient this model so the front of the model is face down to the build plate. Enable supports so that the large curved front can be printed more cleanly. You can block supports on the screw holes for the backplate, and for the mounting hole for the switch (this can be seen in the image above).
• Jaw - Orient the jaw the opposite to the skull, so that the rounded front of the jaw points up. Enable supports so that they support the overhanging teeth, and the large cut-out sections below the gear slide (this can be seen in the image above)

After printing there is a small amount of post processing to do in order to get everything clean. Remove all the supports from the Skull and Jaw and then use a combination of a craft knife and sandpaper to get a smooth finish on the surface. If you want to paint your skull, this would be a great time to whip out some acrylic paints and get creative!