Hackaday Prize Entry: Robotic Prosthetic Leg Is Open Source And 3D-Printable

We’ve been 3D-printing parts for self-replicating machines before, but we’ve been working on the wrong machines. Software and robotics engineer [David Sanchez Falero] is about to set it right with his Hackaday Prize entry, a 3D-printable, open source, robotic prosthetic leg for humans.

[David] could not find a suitable, 3D-printable and customizable prosthetic leg out there, and given the high price of commercial ones he started his own prosthesis project named Drakkar. The “bones” of his design are made of M8 steel threaded rods, which help to keep the cost low, but are also highly available all over the world. The knee is actively bent by a DC-motor and, according to the source code, a potentiometer reads back the position of the knee to a PID loop.

drako_footWhile working on his first prototype, [David] quickly found that replicating the shape and complex mechanics of a human foot would be too fragile when replicated from 3D-printed parts. Instead, he looked at how goat hooves managed to adapt to uneven terrain with only two larger toes. All results and learnings then went into a second version, which now also adapts to the user’s height. The design, which has been done entirely in FreeCAD, indeed looks promising and might one day compete with the high-priced commercial prosthesis.

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19 thoughts on “Hackaday Prize Entry: Robotic Prosthetic Leg Is Open Source And 3D-Printable

  1. It looks really cool. I always apreciated this kind of projects. My mom may need a prostectic knee in a few years. I always wonder if i could make an externat exo-skeleton like knee, to extend the life of her knee and relief the contant pain that she suffers when she walk.
    Something like the EVS knee brace, but made to support part of the weight of her body may help her alot.

    1. Such braces exist. I knew a person that had weak leg muscles and problems with shortened tendons, she used braces on her legs to walk. They had bendable knee joints that locked when leg was straightened. It made walking a bit awkward – Imagine walking with pipes on your legs. And these braces were custom-molded to fit her legs at a price of 10kPLN per brace…

      1. I never saw one. Do you have a link or pic?
        I always wonder how to make one that is confort enought but works well.
        I remember i saw a video when people thermoform plastic bottles over plaster molds to make a close fit to the stump on amputated pacients.
        I could make a more classic vaccum forming using two halfs shell of each side of the knee and see if it clamps to the leg well enoguht to transfer part of the weight to the foot. Otherwise i have to make an entire exoskeleton leg from the hip to the foot, and that wouldn’t be the best for walking.

  2. Did you use the FEM workbench in Freecad to design this prosthetic leg? If yes, do you plan to document your use of the FEM workbench? I would be very interested for my own projects.

  3. “design entirely done in FreeCAD”. Kudos for a very nice result, but i sure hope he doesn’t have to edit a part. The latest version has come a long way, but parts still go out of sync when going back to edit something.

  4. what is the motor all about then, how do you control it with your thoughts or something? or a mobile phone app probably!
    how long does it take to move a single step waiting for the motor to bend the knee? where did the video of it moving come from it’s not here.

  5. Very nice to see more and more approaches to actually usable, sane prosthetics (instead of the “I am a cyborg, I injected an Arduino into my rectum!” hype). Really like it.
    What I always wonder about when trying to understand knee prosthetics is the “rest” versus “bend” function. The human knee (and, obviously, some animal knees as well) has to have a resting position in almost straight down pose where it can support the full body weight, while also allowing for rather rapid acceleration in motion, and some impressive durability in bent position … it’s quite obviously not “intelligently designed”. Obviously, because it *works*, even if it is overly complex (which an “intelligent” designer wouldn’t have had the needs for :D )

  6. So little bit of an industry point here, but I am a little worried about his design. 3D printing a hand is one thing, but 3D printing a leg without a clinician to fit the device is a recipe for a disaster. I cannot tell you how many times we have had patients come in who have just made a “little adjustment” to their legs only to mess up their gait and subsequently their back (or in one case even tear their residual limbs skin).

    1. Most likely would indeed be fit by one–just far, far less expensive to do the actual acquisition portion this way, and definitely far easier to replace anything that broke.

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