Cyborg Beast Hand

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Ever want to lend a helping hand to people who need them?

The Cyborg Beast Hand is a 3D printed prosthetic hand from the non-proft organization e-NABLE. Designed by Jorge Zuniga, users push against the prosthetic with their wrists to make the fingers bend. e-NABLE also offers many different models on their website for people who have different needs and preferences. I received the idea of doing e-NABLE Prosthetics after our engineering teacher, Ms. Berbawy, introduced it to our Principles of Engineering class. My partner and I decided that we would pursue it as our Side Project and worked together for the past few months creating our own prosthetic hands. We have now received badges for our prosthetics, meaning we will continue to create more hands and eventually for clients of our own.

Materials:

  • Cyborg Beast Hand Materials Kit

Tools Necessary:

  • 3D Printer and Filament (PLA)
  • Tweezers
  • Scissors
  • Screwdriver
  • Sand paper
  • Exacto knife

Step 1: Printing the Parts

The STL files can be found by this website.

You will need to 3D print 4 finger phalanges, 4 fingers with or without bumps, 1 thumb phalanges, 1 thumb, 1 normal gauntlet WITH tensioners (Very Important), and 1 right or left palm.

Suggested print settings are shown on the e-NABLE website. The settings are shown from the pictures attached to this post. When I decided to 3D print, I used "Zelda," one of our Ultimaker 2+ 3D printers, under the surveillance of my classmate Sai Kesari. I used Polylite PLA in the color "True Green" for the entire prosthetic, but you can use any color you desire.

To look at other models of prosthetics by e-NABLE or are interested in them, please go to this link.

Step 2: Plan to Assemble and Remove Any Supports

After all of your prints are finished printing, its time to start assembling. Before you start, it is necessary to remove all the supports that are attached to the prints. I found it helpful to use tweezers in areas where the supports are small and difficult to take out. After removing all the supports, I used a rotary tool to smooth out the rough surface created by the supports. You can also use sandpaper as well. After this, I put the rubber grips over the 4 fingers and thumb so it will be easier to work with during the process. Beware, as the grips can feel weird and become dirty.

Step 3: Assembling and Connecting the Fingers and Thumb to the Palm

Starting with the fingers, slide a 1/2" Stainless Steel Chicago screw through both the finger and finger phalange so that they connect at a joint. Screw in the cap on the other side of the screw, taking care to not completely tighten the joint. This will result in stiff joints that are hard to move. Repeat this step 3 times till you have 4 pairs of connected fingers and finger phalanges.

Now, align the 4 connected fingers with the palm. Then, slide a 3 3/4" Stainless Steel Chicago screw through all the fingers and the palm. Screw the other side thoroughly, but not overwhelmingly tight. This is to ensure that the joints move smoothly, as indicated in the paragraph above.

For the thumb, slide a 1/2" Stainless Steel Chicago Screw through the thumb and thumb phalange. Tighten at the other side, taking care to not completely tighten the joint as well. Now, take another 1/2" Stainless Steel Chicago screw and put it through the finger and palm. By doing this, you have now connected the thumb to the palm.

Step 4: Add Foam Onto Preferred Surfaces

For the arm to be comfortable, you can apply pieces of foam onto your hand. The foam from the kit has an adhesive side, which I utilized to stick onto the prosthetic.

The foam used depends heavily on the scaling and overall size of the prosthetic. Therefore, I used a ruler to measure the length and width of the gauntlet, later marking them down on the foam. I cut the foam pieces out using scissors and an X-Acto knife where the cut was not clean. After, I took off the adhesive protector and stuck both pieces onto the sides of the gauntlet.

Using the same tactic as the gauntlet pieces, I measured out the length and width needed to cover the wanted surface area.

Step 5: Connecting the Palm and the Gauntlet

There are two holes that enable the connection of the palm and gauntlet. They are located on the top of the gauntlet and at the very edge of the palm. First, align the two holes together. Then, slip a 3/8" Stainless Steel Chicago Screw through them and tighten at the ends. However, do not tighten enough to the point that the prints will break and make sure that the joint moves well.

Step 6: Incorporating the Elastic Onto the Fingers:

The elastic is to add tension within the fingers and thumb so that they would function as a real hand would do so. If someone were to bend a finger, the tension from the elastic would bring it back to its original position.

To begin, tie a double knot at one end of the elastic. Then, sliver the opposite end into the opening on the front of the finger. Continue to push the elastic through the holes leading up to the top of the palm. Once your elastic reaches the palm, push the elastic through the hold adjacent from its current position. Repeat 3 times for the other 3 fingers till all the elastic strings are on the inside of the palm.

Now, take the two first elastic strings and pull together till you feel the tension from the elastic. Do not pull too hard, as the elastic may break and you will have to start that finger over. Too much tension is also harder to bend, so try finding a nice medium where the finger is movable and tense. To test if you have enough tension, bend the fingers down and see if they come up nicely. If so, create a double knot to secure the tension of the two fingers. If not, pull more on the elastic until it does so. Then, create a double knot and cut the ends off using scissors. If the end of the elastic becomes frayed, you can also use a lighter to singe them. Frayed ends may make it harder for you to push the elastic through the holes. In the end, cut off the elastic from both ends so that there is not a lot of spare elastic hanging on the hand.

Step 7: Incorporating the Elastic Onto the Thumb:

First, push the elastic up the tip of the thumb and let the elastic follow the holes on the thumb. Push until the elastic reaches to the palm. Then, put the elastic through the hole adjacent from its entrance (as shown in the picture attached). After, pull the elastic back in using the hole directly above it. Now, pull tightly until the thumb is completely straight and you feel tension on the elastic. Do not pull too hard, as the elastic may break. But make sure you are applying enough force for the thumb to bounce back when you bend it. When you are happy with the tension, loop the end of the elastic under the portion that stems into the thumb. After, create a double knot and trim the edges. Use a lighter if the end of the elastic frays.

Step 8: Using the Non-flexible Braided Fishing Line

Pull the fishing line through the hole at the very tip of the finger. Then, run it through the corresponding channels and holes until you get to the palm. Similarly, run the thread through the palm until you reach the end, and the string pokes out of the palm. After, cut the thread to where the tensioner pins will be. Give ample extra line, because it will be easier to do the knots with more fishing line. Repeat this process for the other 3 fingers and 1 thumb.

Step 9: Put the Screws Into the Tension Pins

Take 5 large tension screws from the kit and find a screw driver to now attach the pins to the screws. Use a screw driver to attach the pins to the screws. Keep screwing in until there is a little bit of room left for the pin to comfortably move back and forth. This will allow the fingers to bend when the wrist bends as well. If the screws are too big for the tensioner, use a drill to drill through it. They should be able to freely move through the tensioner portion of the gauntlet.

The screw sizes depends on how large your tensioner pins are. The screws, with ample force, should be able to be screwed into the ends of the tensioner pins. If they do not, there are X-small, Small, and medium sized screws that come in the kit as well.

Step 10: Tie the Fishing Line to the Tensioner Pins

To be fair, when I was tying the fishing line to the tensioner pins, I repeated the video tutorial from the 3D Universe because I couldn't understand the instructions. Thus, I will just refer to the following video below, as I feel it is the most helpful way to learn this step.

For a more in-depth tutorial, go here.

Step 11: Superglue the Fishing Line Onto the Pins

Using superglue, stick the fishing line onto the pins. I recommend using a less viscous solution so it will dry faster, but be careful as the glue may spread onto your hands. Do not put a lot at once or douse the fishing line with superglue. That's just wasting superglue that you can use on other projects.

After the superglue dries, proceed to cut off the fishing line excess on the pins using sharp scissors or wire cutters. If the ends become frayed, use a lighter to singe the ends together. Please be careful when using a lighter and do not burn yourself or the print. The print is made of plastic, so too much heat within contact will melt its surface.

Step 12: Attach the Velcro Onto the Hand and Gauntlet

Now, cut out two pieces of 12" Velcro. After, align the pieces of Velcro onto the gauntlet and palm where it will be placed. Use a white marker to indicate the holes for the Chicago screws. Now, use a hole puncher, or any tool that will allow you to create holes in Velcro, so puncture the indicated holes. Fit the 3/8" Chicago Screws through the holes as well to make sure that they will fit with ease.

One side of the Velcro is soft while the other is rough to the touch. Attach the rough side onto the gauntlet so that the skin is in contact with the softer side. Now, after aligning the Velcro holes with the holes on the prints, insert the Chicago screws and tighten all the way.

After these steps, take two pieces of 8" Velcro and cover the Chicago Screws' ends so that the skin does not contact the cold metal. This will maximize comfort for the client as well.

Step 13: Finished Product:

After all of these steps, you are officially done!

I then filmed a brief video explaining the mechanisms of the hand in hopes of receiving the Cyborg Beast Hand Badge from e-NABLE. A few days after, I officially received the badge from e-NABLE, as shown above. I also submitted a badge request for the assembly, which I will hopefully hear back from in a couple of days. After I receive that badge as well, I am allowed to make the Cyborg Beast Hand for people who truly do need them.

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    2 Discussions

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    gm280

    4 weeks ago

    Interesting project to say the least. I realize we have tendons on both top and bottom of our hand and finger joints. But we also have the ability to spread our fingers and even turn our thumbs to a degree that man has yet to mimic with trying to build a duplicate. But it is getting there one day that keeps the interest. Thumbs Up, pardon the pun....

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    jessyratfink

    4 weeks ago

    This is a great write up of the whole building process! What a great company to work with. :)