Prototyping Toolkit for Prosthetic Arm Extensions

About: > Master Industrial Design, Ghent University

As shown in the pictures, this Toolkit can be attached to a Prosthetic Work-Arm to allow persons with an arm amputation toattach 'low-tech' tools to their prosthesis. Its goal is to give these persons the ability to test and prototype prosthetic arm extensions and search for the right dimensions and positioning. All of the toolkit's components were designed to be 3D printed, laser cut or are off-the-shelf available. In this way, a tailored and custom-made Assistive Tool can be achieved.

The Toolkit is extremely useful in a rehabilitation environment, as it allows the occupational therapists, patients and other thirds to co-create custom-made DIY assistive technology, perfectly fitting the needs of one patient. Once the person knows which position, dimensioning and adjustability is comfortable, the tool kan be reproduced easily in steel or other more durable materials.So, the Toolkit mainly functions as a prototyping and testing step before an Assistive Tool is immediately made out of steel.

The kit was designed for digital production, existing of 3D printed and laser cut components. As an example, some pictures were added of a the prototyping phase for a wrench-aid. Feel free to design & share new components for other applications, it can help a lot of people worldwide!

All files can be found on the Thingiverse page:

Feel free to 3D print your own toolkit or make & share your own tool connections for other applications!

Step 1: Collecting the Needed Off-the-shelf Available Components

To assemble the toolkit later on, these components will be needed:

> M5x30mm bolts
> M5 wing nuts
> 4mm diameter axis with a length of 13mm (you can use a nail, etc.)
> Eventually zip ties, ropes or other connection tools...

Step 2: 3D Printing the Different Components

The 3D printed components were designed to be printed on every machine, even the cheaper desktop machinery. If you don't have your own 3D printer, you can take advantage of the growing number of fabrication laboratories, 3D hubs and 3D printing services.

I used 'Polymax PLA' ( on an Ultimaker 2.0 to print the parts. If you decide to print your own version at homeor produce your toolkit in a fabrication laboratory, I would recommend this filament. Also, I would recommend a minimum infill percentage of 50% and a layer thickness of 1,2mm.

If you let the parts be printed by a hub or service, ask them for adurable and tough material that fits your budget.

All files can be downloaded on Thingiverse:

Step 3: Laser Cutting the Extension Pieces and Rings

To adjust the length of the Prosthetic Arm Extensions, a laser cut cross was designed to be used as an extension piece. Also, a set of rings can be laser cut to let the joints move freely instead of being fixed in one position. For the sheet material to be laser cut, I recommend ABS or PA with a thickness of 3mm.The strength is mainly in the structure so it should work with other materials too. Though, plexi glass for instance will be too brittle and wood won't be durable when used in water...

If no laser cutter is available, the laser cut crosses can be replaced by off-the-shelf available, square profiles of 15x15mm.These files were also added on Thingiverse.

All files can be downloaded on Thingiverse:

Step 4: Assemble the Toolkit and Attach Tools

Themodular toolkitallows you to assemble the components in many ways. The pictures above give you some ideas on how to assemble the kit. All kinds of tools can be attached to the kit...

Step 5: Connect the Toolkit With the Prosthetic Work-arm

The toolkit can be attached to a prosthetic work-arm or a myo-electric prosthetic arm, using the pin connection shown above. For strength reasons, I recommend to use an off-the-shelf available axis with a diameter of 4mm and cut it to a length of 13mm instead of 3D printing this axis. Also, the files on Thingiverse were designed this way...

Step 6: Test, Learn or Make Your Own Tool Connections

In a rehabilitation context, many useful tests can be done with this Toolkit. Patients, occupational therapists and other thirds can explore and test very quickly what is useful and good for one specific case.

On this instructable, I give some examples of a case in which a person needed a wrenching aid.
Feel free to test your own applications and make your own tool connections if needed.
On thingiverse, different connections are already shared, as a connection for zip ties and a screw clamp.

Step 7: Optional: Reproduction of the Outcome Out of Steel

Once a comfortable and functional outcome is found with this toolkit, the assistive tool can bereproduced in steel or in another durable material if necessary. Of course, for some applications the 3D printed model will suffice.

It can be useful to use these off-the-shelf available serrated rings:

3D Printing Contest 2016

First Prize in the
3D Printing Contest 2016



    • Pie Contest

      Pie Contest
    • Weaving Challenge

      Weaving Challenge
    • Remix Contest

      Remix Contest

    9 Discussions


    2 years ago

    Nice! I love it. I did a similar project about a year ago.

    2 replies

    Reply 2 years ago

    I already saw your project a few months ago! It really looks great :)
    Great work too! Are you still busy with these things?


    Reply 2 years ago

    Glad you liked it. I am not working on prosthetics now, but I hope to revisit the project again in the future.