Introduction: How to Develop Your Own DIY Prosthetic Based on Your Needs.

About: i have spent my life finding alternative ways to get every task done in spite many challenges. most of my projects are as we call how we do things Fabrecobled (to make (fabricate) something from whatever layin…

This is my first Instructable and it is ambitious and still an ongoing project so please forgive any mistakes or missteps I will be editing the Instructable as the project progresses.

I am a long time (35+ years) amp (amputee) above shoulder left arm and recent graduate from Wichita State University with a bachelor's of Civil Engineering Technology. I started this project because my arm was failing and finally felt the need for an assistive device. I was able to use the project as a research requirement for my degree. As the project continued I started applying senior design ideas to this project and this Instructable is done using every thing learned and intended to guide you through the process in a way that may (hopefully) save you much time and frustration. This project is still vary much in progress.


You will need (depending on your skills and flexibility).

  1. Open mind.
  2. Willingness to fail (it happens a lot).
  3. Research tools (if you are reading this it's safe to say you have a computer and internet).
  4. An ability to make/represent the parts you designed. (I mostly used Solidworks but after using Fusion360 I highly recommend that instead (it's free to hobbyists) Tinkercad may work for your needs).
  5. A way to mount the device to yourself. (I'm using a 3D scan of my body and 3D printing (there are other ways)).
  6. Basic shop tools, skills and knowledge (Your safety is your priority take it as seriously as you are willing to accept the risks you take. Do not put others at risk!)
  7. Willingness to ask for help as needed

Step 1: What Do You Need in a Assistive Device?

This is the hardest but most important step.

Think long and hard about the tasks you preform every day and think what actions or tasks an assistive devise could do to improve the completion of those tasks.

List off all the wants and needs you have in a device. Mine looked like this.

  • EEG controlled by my hat
  • Interchangeable tools at working end (chain saw hand yes please)
  • Match my arms strength
  • Affordable to build and maintain
  • Dexterity compared to my hand
  • Interchangeable battery with my power tools
  • Hold things

I think that was about it, I didn't write it down (Remember this is how I should have done things knowing what I know now.)

Years of thought went into this and I determined that tentacle like device (You just fell into the gutter didn't you? When you climb out continue reading.) would fit my needs well.

Through my contacts in the amp community a few problem statements arose that may or may not pertain to your use or in the continued Instructable but here they are anyway.

Problem statements.
1. Find a way to improve functionality of working end of upper limb prosthetic.

2. Find a way to improve the availability of working end of upper limb prosthetic.

3. Find a way to improve affordability of working end of upper limb prosthetic.

Step 2: Self Educate.

Study what is required to get your device to do what you want it to do. Instructable is a fabulous resource for researching anything DIY.

I researched my daily activity's and how others do the same tasks. An observation made during this observation period was that many tasks require fixing an object at one end and manipulating another point to complete the movement. Sweeping with a broom is the task I use as an example. My father in blue holds the end of the broom mostly stationary at his chest and manipulates with other hand. I use my armpit to hold the end and manipulate with hand. (This puts the tasks full load on my shoulder.)

Also studied: EEG control, motors, battery, myoelectric control, Arduino, design software, 3D printing and scanning, traditional prosthetic fitment, soft robotics.

Step 3: Minimize the Unnecessary and or Tech Beyond Your Tolerance Levels.

Strip away every thing that you don't want or need after your research.

I striped away

  • EEG hat control
  • super strength
  • interchangeable working ends

I wanted to consider a powered device as long as possible; because a traditional body powered unit won't work well for my body configuration.

Step 4: Start Designing and Testing.

Doodle, cardboard, computer design programs, whatever it takes to put enough pieces together to get an idea of what may or may not work.

I designed and printed the working end "tentacle" so it could flex in both directions. Epic failure! When I load tested it, it buckled instead of curling. I learned more that day in the design process than at any other point (so far). What I learned was that you must constantly repeat the steps you have taken with the new knowledge you have gained.

So go back to step 1 and repeat all the steps until you end up with something you can be happy with.

This is where using a 3D scan of my body to design the body mount was chosen. And I had to educate myself on how to use a STL of a point cloud and turn it into a manipulable object. The fusion360 videos were very helpful with this, though I had to use a different technique. (This will be its own Instructable later.)

List as of now from returning to step 1.

  • hold object to be manipulated by hand
  • light weight
  • simple to use
  • affordable to build and maintain

Step 5: Build, Test, REPEAT All Apropreat Steps With New Knoledge.

Build it. Using the tools at your disposal there are many 3D printing resources on line if needed, I have access to the WSU equipment and my own home shop.Test it. Use some common sense here and be safe.

Some of my test videos so far. Every test failure (applied learning) drove a necessary repeat of any number of the previous steps. TIP; use permanent marker to note the adjustment needed for the next test on the prototype, this aids in keeping track of what needs to be done.

This test used 50lb braided fishing line (that broke) under the power of ~3in wide strip of bike inner tube as the spring.

This test uses ~1in band from bike inner tube and the 50lb line (this
worked), a way to adjust the length of the cable so the spring can function properly is needed.

Mouse trap power a solid solution to the above problems of getting controllable tension on the fishing line. My kids are fighting there naps and one fell and went boom, everyone is OK.

Assembly and adding tension to mouse trap spring pack.

opening cable broke devised pulley system (needs changed to keep fishing line in the track), shoulder update.


If this is for yourself and have been designing it all along you have probably observed the potential risks to using the device and designed in safety and or accepted the risks, though its advisable to complete the ethical training described below.

If you are helping someone design a device or designing it for some one, complete human testing ethical requirements. Any university with a medical or engineering programs should be able to at least point you in the right direction or help with this, or if your google foo is better than mine there are online resources.

Step 6: The Final? Design, and Use. (have Not Yet Got to This Part But This Is How It Should Go)

Build and assemble your finished design in higher quality materials. (I'll be printing parts in a carbon fiber or glass fiber filament.)

Use your new assistive device, (prosthetic, what ever you want to call it).

Be honest with your self this is only the first of many versions that you will make. Because through use, improvements will become apparent and you probably will do what you can to improve your life. (I certainly will continue to make improvements.)

Repeat all steps with new knowledge.

Assistive Tech Contest

Participated in the
Assistive Tech Contest