NormaCore ElRobot

ElRobot is a fully 3D-printable 7+1 DOF robotic arm designed by the NormaCore team for affordable physical-AI research and imitation learning experiments.

With 6 main joints plus a parallel jaw gripper as the 7th degree of freedom, ElRobot covers a wide workspace while remaining lightweight and low-cost — the full build runs around $220 in hardware including 7 STS3215 serial bus smart servos, which are the same servo family used in leading open-source arms like SO-ARM100.

The arm ships with full URDF + mesh support for simulation (NVIDIA Isaac Sim, MuJoCo, ROS 2), making it dual-purpose: train imitation learning policies in simulation and deploy directly to the physical hardware without modification.

Key specs:

• Joints: 6 rotational (shoulder pan/tilt, elbow, wrist pitch/yaw/roll) + parallel jaw gripper
• Servos: 7× Feetech STS3215 serial bus servos (TTL half-duplex, 12V)
• Print time: ~14 hours total across all structural parts
• Filament: PLA+ recommended; PETG for high-cycle gripper jaws
• Payload: ~200g at full extension
• Build cost: ~$220 USD (servos + hardware kit; printer not included)
• Simulation: URDF meshes provided in hardware/elrobot/simulation/

Imitation learning workflow: NormaCore provides a full teleoperation stack based on LeRobot. A leader arm (or SpaceMouse) records demonstrations which are replayed and used to train ACT / Diffusion Policy models. The simulation assets in this repo mean you can augment real demonstrations with synthetic rollouts for data-efficient policy learning.

Build this robot: Full BOM, assembly guide, and wiring diagrams are in the NormaCore GitHub repository. STL files for all structural components are embedded in this program for 3D printing reference.

Hardware licensed under MIT. Software stack licensed under MIT. Original design by the NormaCore team — https://github.com/norma-core/norma-core

Build Guide

Assembly manuals (PDF) and hardware files: github.com/norma-core/norma-core/blob/main/hardware/elrobot/README.md

Printing

This is the part set for a single ElRobot follower arm (6 rotational joints + parallel-jaw gripper). Parts are the individual STLs from the upstream repo (hardware/elrobot/STL/elrobot_individual_parts/), one STL per physical part. Recommended filament: PLA+ for structure, PETG for the gripper jaw. ~14 hr total print time.

Arm structure — print one each (14):

• Base, Base_Shield
• Joint_1
• Joint_2, Joint_2_Shield
• Joint_3, Joint_3_Shield_Camera_Side, Joint_3_Shield_Drive_Side
• Joint_4, Joint_4_Shield
• Joint_5
• Joint_6, Joint_6_Shield
• Wiring_bracket

Gripper — print one each (4): Gripper_Base, Gripper_Base_Shield, Gripper_Gear, Gripper_Jaw

Controller enclosures (4): This build uses both a Seeed XIAO ESP32C3 controller and a Waveshare servo driver board (per the BOM), so both enclosures are included — ss_enclosure_case + ss_enclosure_lid (Seeed) and ws_enclosure_case + ws_enclosure_lid (Waveshare). Print whichever enclosure(s) match the boards you actually mount; if you only use one board, you only need its case + lid.

Camera mount (optional — pick ONE): CameraMount_regular, CameraMount_square_27mm, or CameraMount_square_34mm. Choose the one matching your camera module's mount footprint (27 mm vs 34 mm square, or the regular round mount). Skip entirely if running headless.

Servos (not printed): 7× Feetech STS3215 serial bus servos — joints 1-6 (×6) + gripper (×1).

Removed from the previous list: the 19 simulation meshes (base_link.stl, Joint_0N_*/Joint_0N_v1_1, Gripper_*_v1_1, and 8 ST3215_N_v1_1 servo-body meshes — these are URDF/Isaac-Sim visualization assets, not printable parts), plus the pre-merged build-plate bundles (panels/regular_parts/strong_parts for both leader and follower) which duplicate the individual parts above, and the leader-arm parts (this listing builds the follower arm). Duplicate camera-mount copies were also removed.