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A 16-YEAR-OLD BUILT A FULLY 3D PRINTED ROBOT ARM

A teenager built a 6-axis robot arm from scratch with counterweighted motors, cycloidal gearboxes, and a differential wrist — and says the hard part is just starting.

by u/_Rayolo_

FULL CAD BOM FIRMWARE DOCS

RoboticsWorkshop

Built withSTM32

difficulty
●●●●●
time
months
license
license not specified
repo
repo 0 stars

WHAT YOU’LL NEED

1
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COMPAREE VERDICT

This is a documented success, not a shared project. The creator finished a fully custom 6DOF robot arm at 16, with rear-mounted motors acting as counterweights, cycloidal gearboxes printed in nylon, concentric tubes driving motion up to the wrist, and a differential wrist mechanism driven by belts. The electronics are fully custom with TMC2209 and TMC2160 motor drivers and an STM32F103 microcontroller programmed in C++ and Rust. It is genuinely impressive engineering. But the post does not link any files, firmware, parts list or build guide. The creator is still working on control and inverse kinematics, and openly asks for direction on computation offloading and pin mapping. If you want to build a 6DOF arm, this is proof it can be done by a determined teenager with access to a 3D printer and PCB fabrication, but you will have to design your own from first principles. The one thing most likely to go wrong if you try to replicate it: underestimating the control software. The creator says that is the hardest part, and they have been working on this since they were 14.

GOOD TO KNOW

  • —The Reddit post does not link a repository, CAD files, firmware, a parts list or build instructions.
  • —This is a single Reddit post with photos and a written summary of the build.
  • —The creator describes the mechanical design (cycloidal gearboxes in nylon, PLA for the rest, concentric tubes, differential wrist) and the electronics (custom PCBs with TMC2209 and TMC2160 drivers, STM32F103 microcontroller), but does not link the files.
  • —The creator is actively working on inverse kinematics and control, and asks for advice on offloading computation to a Raspberry Pi or PC.
  • —No licence is stated, because nothing has been released.
  • —You cannot build this exact arm from the post alone — treat it as a reference for your own design.

Parts to buy

7 items

From our check of the build. Exact quantities and part numbers are in the creator’s BOM.

  • TMC2209 and TMC2160 motor driversFind
  • STM32F103 microcontrollerFind
  • Nylon and PLA filamentFind
  • MotorsFind
  • BeltsFind
  • BearingsFind
  • Custom PCB fabricationfrom the repo files

Can I build this?

Printno printable files are shared
BuyTMC2209 and TMC2160 motor drivers, STM32F103 microcontroller, nylon and PLA filament, motors, belts, bearings, custom PCB fabrication
Tools3D printer with nylon capability, PCB design software, embedded programming environment for STM32, soldering station
Skillsadvanced mechanical design (gearboxes, linkages, differentials), PCB design, embedded firmware in C++ or Rust, inverse kinematics, motion control
Timemonths to design and debug from scratch
Cost$$ dominated by motor drivers, motors, custom PCBs, and nylon filament for gearboxes
SafetyStandard electronics care. If you are replicating from scratch, take care with motor power supplies and moving mechanical assemblies.

Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.

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Start here

Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.

  1. 1.Read the Reddit post (This is the only public source, and it does not link files.)
  2. 2.Research cycloidal gearboxes for 3D printing(The creator used these for the base and shoulder. You will need to design or find your own.)
  3. 3.Study differential wrist mechanisms(The creator is proud of this part. Understanding the kinematics is essential.)
  4. 4.Plan your control strategy before you build(The creator says control is the hardest part. Decide whether to run inverse kinematics on the microcontroller or offload to a Pi or PC.)

KNOWN ISSUES

  • The post does not link any files, so you cannot build this exact arm from it. Use it as design inspiration.
  • Cycloidal gearboxes in nylon are non-trivial to print and assemble. Expect tuning and iteration.
  • The creator is still working on inverse kinematics and control, which means the software side is unfinished even for them.
  • Underestimating the computational load on an STM32F103 for real-time inverse kinematics. The creator suggests offloading to a Pi or PC for a reason.
  • Pin mapping across several motor drivers is still open in this build — the creator asks for advice on it.
  • Custom PCB design and embedded programming in C++ or Rust are advanced skills. If you have never done either, this is not the first project to try them on.

Are the STL files available?

The Reddit post does not link STL or CAD files. It is a build showcase, not a release.

Is the firmware shared?

The creator mentions programming an STM32F103 in C++ and Rust, but the post does not link the code.

What motors were used?

The post does not specify motor models. The creator uses TMC2209 and TMC2160 drivers, which handle stepper motors.

Can an STM32F103 handle inverse kinematics in real time?

The creator is unsure and is considering offloading the computation to a Raspberry Pi or PC. That is a genuine open question.

How much did this cost to build?

The creator does not give a cost in the post.

Is this ready to use?

No. The creator is still working on control and inverse kinematics.

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Discussion1

FROM THE COMPAREE TEAM

The creator says inverse kinematics on an STM32F103 might not be fast enough and is considering offloading to a Pi. If you have built a 6DOF arm, what did you run the IK on?

CompareeTEAM1d ago

This page is based on the creator's Reddit post. It is a documented build with photos and a written summary, not a repository or a release. The mechanical ingenuity is real — cycloidal gearboxes in nylon, rear-mounted motors as counterweights, concentric tubes, differential wrist — and the electronics are custom, but the creator is still working on control software and openly asks for advice. If you want to build a 6DOF arm, this is proof that a determined teenager with a 3D printer and PCB skills can do it, but you will have to design your own version from scratch. The single biggest challenge the creator names is inverse kinematics and real-time control, not the mechanical build.

u/_Rayolo_

The creator started this project at 14 and finished the mechanical and electrical build at 16. They describe it as a learning vehicle for mechanical design, PCB design, and embedded control systems, and are now working through the control software.

Star the project on GitHub

DISCLAIMER

  • Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
  • Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
  • Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
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