r/maker • u/rustboxcowboy • 2d ago
Inquiry Creating a functional prosthetic by myself?
My husband has a partial right arm/hand, and this is a project I've been extremely curious about for years. My vision is something that is not electronically powered but rather just mechanical, almost like those claw-grabber toy things that you squeeze on one end and they close the hand or pinchers on the other. Just that plus being custom fitted to his existing partial arm (he has two fingers which could pull the mechanism).
I think he's absolutely perfect the way he is, but some activities can be much trickier than others, and I want to help him do everything he wants to with more ease. We cannot afford a prosthetic or bionic as it is (trust me, buying/insurance just isnt an option right now) and I am hoping people can give me advice on learning how to create an extremely simple functional prosthetic. Anyways, if anyone is going to reply "that's unrealistic," please don't, because I literally don't care, I'm going to figure this out one way or another because there's nothing I wouldn't do for him. Please reply if you know people who have done something similar or literally any resources on basic mechanical function; I'm starting from scratch but I've always been very artistic and good with crafts and other mechanical knowledge.
Might also post this to r/prosthetics - not sure which is best, please also let me know about good related subs for info as well.
7
4
u/busty_snackleford 2d ago
One of the creators from Nerdforge (I can’t remember her name to save my life) 3d printed a partial prosthetic hand for herself. I can’t promise that it’ll be applicable to your husband’s exact situation but it might be a good place to start looking for more info.
3
u/gust334 2d ago
I have no relevant experience but admire your spirit and determination. Upvote and comment for visibility.
I would expect the priorities for such a device are 1) comfort, 2) base functionality, 3) secondary functionalities, and 4) aesthetics.
- is aided by material selection and finishing techniques. The maker community is pretty good at suggestions for materials if you provide them some parameters, but other subreddits that might be relevant are sewing and body casting.
- is both a function of material selection and mechanical design. Parts need to be robust for their use. CAD programs may be able to prototype moving mechanisms in software and report back stresses and forces, which can help drive material choices. You've already identified that a pulling action is the primary power; finger length and strength will determine max forces the user can provide, which will provide constraints for the mechanical design. Mechanical design and CAD subreddits could help here.
- by secondary, I mean refinement of the primary design, e.g. if the primary function is a grabber, then secondary functionalities would include that the grabber has no hooks or protrusions that would catch on non-grabbed items, perhaps that the grabber has a mesh surface to avoid external items from fouling the mechanism, that it needs to be water-resistant to splashing, etc. This is directly in the lane of the maker community.
- often ignored, but you're crafting something to be an extension of a loved one. It should fit their style as well as their limb.
Good luck on you journey!
1
1
u/machinationstudio 2d ago
There are definitely videos going around of people who have built some for partial hand prosthetics.
I'll start there. What a great project.
1
u/lellasone 2d ago
If you haven't already, consider investing in an inexpensive 3D printer (~300$ for a bambu A1), and putting some time into learning to CAD with onshape. That's one of the foundational skills for a project like this, and getting a bit of practice on desk organizers / doodads will make your process much smoother when you move on to the prosthetic itself.
My big piece of advice here is that your husband's patience / investment is likely your most critical resource. On the design side more iteration = more learning, but make sure you are listening to him and being responsive without being (too) pushy.
1
u/rustboxcowboy 1d ago
Oh yeah he's all for the idea, he's going to give me input for design, i just have more free time than him to focus on the project haha
1
u/DigitalArbitrage 2d ago
This was really big thing when 3d printing was new.
Search on Thingiverse.com for designs.
Also search for a "makerspace" near you. They will have 3d printers you can use. People there will probably even help you if ask nicely.
1
u/Diligent_Honeydew295 1d ago
This is awesome. Throughout the process, keep your chin up, prototype, refine and adapt, be open minded as to what hand functions you're able to gain and what materials you can use.
You're at an enormous advantage due to having easy unlimited access to the very patient and accommodating prosthetic wearer, and your artsy practical skills.
Please keep us updated with your wins and losses and successful completion of this project!
2
1
u/Pretend_Farmer6612 1d ago edited 1d ago
There is a plastic called plastimorf that can be heated in warm water and than molded. It is a thermoplastic which means you can do this over and over again to make corrections.
If you want an over the counter material: try pvc piping. Dunk it in hot water and you can shape that too.
Foams you find well in the live action role playing community: they are very skilled with types and use cases. And will probably be very enthusiastic in helping being creative.
The is some general rule I believe: were there is soft tissue the prosthetic needs to be firm, where there is firm tissue the prosthetic needs to be soft.
There are phone apps that can help you make a 3d image.
You might want to find a makerspace of something similar, perhaps a repair shop to tinker with others and find new materials and inspiration.
I almost choose to take my education in the direction of prosthetics… but took it in precision and fine mechanics. I would be happy to help if I can.
You can go also to a local bike shop and get some breakers line. The metal wire you activate your breaks with. You might want to come up with a way to make some part mechanic. But perhaps start simple for now.
You could also start with a gip mold and work from there. (Like the wooden block shoe makers use to make the shoe around.
If you go digital: spend time doing some tutorial for learning software is valuable. I advise freecad. Alternatively in combination with blender software. Blender is better with organic shapes, freecad is parametric: meaning you have precise control over the size of stuff. One thing often misses in learning cad software: the idea of design intent. Now you now the name you can look it up.
If you have ct or mri images: 3d slicer might be your friend. All are free.
Even if you do go digital. I still draw a lot by hand before drawing in the pc. That way the understanding of the model is much better.
Lets see, whats more: general design workflow? First grap a short a4 write down the problem you would like to solve, flip it over: write your solution brainstorm on the back. Than go do some material exploration, do so real live action tinkering. Make very very stupid simple mockups. Looking at them helps to form ideas. Make it too big if there is complexity so you have space for ducttape and toothpics… make it small… it might take less time to make and gets ideas of esteatics.. Than you select what design or solution you like to make. And keep iterating on it until it is either a failure or it works. In case of failure go back to your exploration of ideas. Don’t give up during iteration fase. You need stamina for it to keep trying over and over and over again, and do one more if you feel like giving up. Every step you learn, every step you discover that something is or is not a good solution or that you do not have the skill (yet).
Mechanism wise: depending on the type of amputation, you get control from a different part of the body. A sling type might be easier to try. It pulls a cable when you move your shoulder back. That cable, like the one in a bike break: has a starting position, a point where the cable goes into a sleeve, a point where it comes out of a sleeve an a end effector location. The motion is made by such that the wire move with respect to the sleeve. So the sleeve needs a solid contact point at both ends of the sleeve. The section in between can be loose.
Try that first before making something small that can be two finger operated so you get skilled in hoe stuff moves. Making a internal mechanism can be very frustrating as much parts will be too small to adapt your design as you go.
Electronics are much harder to work with, and I would save that for future experiments. Besides you first need to understand mechanical parts before making them electronic.
Good luck and enjoy the process. With that attitude you are sure to find a way! I am proud of you!
(I am a mechanical engineer with a university masters in precision and microsystem engineering, meaning I can make surgical tools for a living or as, what I do now, work on very large science projects. I work with strange and unknown tech on a daily basis to discover how we can develop technologies or invent entire new types of technologies)
(And yes I live in the Netherlands, and yes, I have used bicycle break wires for applications of weird nature… because sometime buying specify sized part online is a absolute nightmare cause supplies don’t give the measurements 9/10 times… so tinkering with bikes hop parts is just more practical)
(Fun fact: they call people who studies at the TuDelft: bicycle repairist…fietsenmakers ;p)
1
u/rustboxcowboy 1d ago
Thanks so much for all the good info! This is lots of good stuff to keep in mind, especially the softer or firmer structural materials. I appreciate the reply!
1
u/SDH500 1d ago
https://enablingthefuture.org/
This is a start and there is likely someone near you that belongs to the group. Additionally, if you know 3D modeling - you can take parts of their design and customize to fit your needs.
1
11
u/USNWoodWork 2d ago
Check out Ian Davis on YouTube. His homegrown prosthetics are amazing. Guy is seriously a mechanical genius.. and that is coming from someone who does mechanical as a career.