Kayra 3D-Printable Open Humanoid Robot (Refurbished)

Kayra is a small humanoid robot you can print at home. The legs, hips, chest and arms are printed parts driven by standard hobby servos. A Pimoroni Servo 2040 controls the body, and an optional ESP32-CAM head streams video to a PC for vision and machine-learning experiments. Everything is designed in FreeCAD, so every part is easy to change.

Updated for modern use: a grouped print table, one purchase list, notes for separate servo and logic power, and a single build guide in build order. The print files are unchanged.

What you build

• Two legs built from the foot up: foot, foot joint, calf and shin, knee and hip joint
• Hip plates that join the legs, a chest base that holds the battery and a chest back that holds the controller
• Two arms with shoulder, upper arm and lower arm
• A Pimoroni Servo 2040 with up to 18 servo channels
• Separate power rails: a 10 A UBEC for the servos and a small 5 V BEC for the controller

Files

• All 27 print-ready STL files of the current design: feet, ankles, calves, shin, knees, hip joints, hip plates, chest parts, shoulders, arms and a servo block
• Build guide PDF: grouped print table, electronics and power wiring, assembly order and software overview
• Bill of Material PDF with quantities, notes and a shop link for every off-the-shelf part

Print settings

PETG recommended. Print one of each file and two of the shin (3FU_shin). Parts named L and R are the left and right versions; the number in each file name is its position from the foot (1) up to the chest (7) and arms (8-10).

Electronics

• Pimoroni Servo 2040 body controller
• Standard-size metal-gear hobby servos (MG996R class) for the joints
• 10 A UBEC for the servo rail and a 5 V BEC for the logic rail
• 2S LiPo pack with XT60 lead, a 10 A power switch and a balance charger
• Optional ESP32-CAM with OV2640 camera for the head

Bill of Material

Every part you need to buy, with quantities, notes and shop links, is in the Bill of Material PDF in the files of this model. The Pimoroni Servo 2040 is bought from Pimoroni (pimoroni.com) or a Pimoroni reseller, and the small ball bearings for the feet and hip joints from a bearing supplier; read the bearing sizes from the FreeCAD files. The build guide lists both.

Software

The robot side runs MicroPython on the Servo 2040 and the ESP32-CAM; the host side is Python for vision and learning. A MuJoCo model of the robot lets you try motions in simulation before running them on the hardware. Test each joint on its own at low speed first.

Skill level

Intermediate to advanced. You centre and fit many servos, wire two power rails and flash MicroPython boards.

Full build guide and source

The build guide, source and all project files: https://github.com/ToolKnox/hawkridge-kayra-3d-printable-humanoid-robot (Code > Download ZIP).

Safety

LiPo and Li-ion packs can deliver very high current. Fuse or current-limit the servo rail, never leave a charging pack unattended, and keep fingers clear of the joints while the servos are powered.