HP Robots | Otto Middle modules

The Middle Modules are the heart of Otto’s modularity. This section sits between the Top and Bottom parts of the robot and was originally designed to hold the main circuit board and battery. But the middle has evolved into much more: a flexible expansion zone where you can stack modules, add spacers, mount displays, swap faces, and give your Otto new personality and functionality.

Whether you want expressive eyes, sensor mounts, extra space for components, or a completely new look, these middle modules let you customize Otto in endless ways.

🧩 What You’ll Find Here

A collection of faces, middle frames, and complementary attachments that slide, stack, and snap into the Otto Starter system.

🔸 Middle Modules

• The “band” between the top and bottom parts of Otto

• Originally for the main board + battery, now a stackable expansion layer

• Add spacers to increase internal room for electronics

• Combine multiple middles to create taller or more expressive robots

• Perfect for mounting displays, sensors, or custom electronics

😀 Faces

• Slide directly into the middle module

• Instantly change Otto’s personality with different eye styles, mouths, or themes

• Support for multiple displays (LED matrices, OLEDs, etc.)

• Can hold sensors such as distance, light, or gesture modules

• Easy to swap—great for classrooms, workshops, and creative play

🔧 Attachments & Add‑Ons

• Decorative or functional accessories that integrate with the middle frame

• Ideal for adding character, tools, or extra interaction features

• Fully compatible with the Otto Starter modular system

All parts are modular, remix‑friendly, and stackable, giving you total freedom to design your own robot style.

🧠 Part of the Otto Starter Modularity

The Otto system is built around three printable layers:

• Top → lights, hats, displays, personality

• Middle → faces, sensors, electronics, expansion

• Bottom → wheels, bumpers, arms, movement

These Middle Modules expand the second layer, unlocking more creativity and technical possibilities.

If you haven’t printed the main Starter Kit yet, you can find it here:

🖨 Print Instructions

• Material: PLA or similar

• No supports, rafts, or brims needed

• Layer height: 0.2 mm or less

• Perimeters: minimum 3

• Infill: 15% or more

💡 Tips

• Mix and match faces to give Otto different moods

• Use FaceUS_flat.stl face extra holes with couple of screws for decorations like glasses, beards and so on, allowing modularity and more colors without multi-material printers or you could think of using magnets too!

• Stack middle modules to add internal space for custom electronics

• Use display‑compatible faces to show animations or sensor data

• Remix your own designs—we love featuring community creations

🌍 Join the Community

❤ Like and share, and join our friendly global community of robot builders, educators, and makers. Join today our Otto Builder community