Movable Hand

When you're doing stuff or holding too many things in your hand, don't you feel like having another hand? This project is exactly what you need. Building this project was a very good experience for me. As a beginner who just started learning CAD and 3D-printing, I saw this as an opportunity to gain more knowledge and new skills related to engineering.

This project is meant for someone who is too lazy to hold their things on their own or just wants an extra hand to hold things. I used Fusion 360 to design my project and printed it using a Prusa Mini. This project was inspired by my laziness: I didn't want to hold my phone on my own when watching anime. Instead of finding a boring phone holder to use, I wanted to design my own.

Materials:

Aluminum Wire for Beading and Crafting

Rubber Glove

3D Printing Spool

Clear Silicone Rubber

Reference:

Bicycle Phone Holder (Wrist)

Wooden Hand Model

Tools:

Wire Cutter

3D Printer

Super Glue

Ruler

The first thing I did to have a general design of the whole project was to create a sketch. In order to know how bones inside the hand are located, I found a video that explained in detail about human hand bones with a 3D model. I made the individual joints of the fingers into trapezoid-like shapes instead of rectangle-like shapes to make the bones flexible and not rub against each other (take a look at the upright corner of image 1).

I used three aluminum wires per finger to connect the bones. Instead of putting three wires in the same hole, I made three separate paths. This way, the wires can stabilize the bones better and won't allow the fingers to move in unnatural ways.

For the wrist, which I based on a bicycle phone holder, I made a ball sandwiched between two arc components (be aware that the ball has to be inside one of the half arc component so it won't fall apart) (look at image 2). At the bottom, I made a screw system for the wrist to be able to lock in a desired position and unscrew it if you want to move it.

After all the designs are were and set up, I started working on making the parts. I used Fusion 360 to CAD the parts, and a Prusa Mini to print them out.

The first part of the project is the finger bones. To CAD finger bones, I made two sketches on different planes and lofted them together. Then, I mirrored the other half of the bone to make it symmetrical and extruded the three hole in the middle of the finger. The front of the finger bone is a little different. To stablize the wires, I made a space on it for the wires to thread in, and made a ball cap to cover them and hold them in place (look at image 2). The whole design will end up looking like the one shown in image 1.

After finish designing the model, I put the components onto Prusa Slicer to prepare to print on Prusa Mini (look at image 4).

After printing, thread the aluminum wires to connect all the components of finger bones (printed products) to make it look like a human hand (see image 5).

I used many planes and sketches to create the wrist part components. I made different sized circles and lofted them into a hemisphere for the inner part of the wrist. On the outside, I used four planes and four circles of different sizes which were lofted to make the component. After that, I created a rectangle and extruded it. See design on image 1.

The forearm is the easiest part to make in the whole project. I just extruded an oval and made circular holes at the bottom and threaded them. I also, made rectangular holes close to the top as a place to place the screw (see image 3). Last but not least, the other half of the semicircle that covers the component shows in image 4.

And then the base. the base is very easy to do too. I used three planes in different positions and three different sizes of circle to lofted and extruded out the base. On the extruded part, I threaded it a little bit smaller than the thread I gave on forearm, in order to let them easier screw in (shown on image 2).

To be able to make it looks like a real hand, I did all the measurements on my real hand. Furthermore, want it to be flexible and touches like a real hand if possible. Under the suggestions of Sven Olson, one of my friends, I decided to use silicone to be the thing that cover the finger bones. I 3D scanned my hand and made a mold of my hand. On the four corner of the mold, I made a hole on each corner for wood sticks to go through and stable the mold. Design model and printed products show in image 1, 2, and 3.

After all the components and parts are done, I assembled them up (show in image 1). Put the finger bones hand into the mold (show in image 2). And then fill the silicone into the mold (show in image 3). Be aware, silicone has part A and part B, use a 1:1 ratio for the mixture, or it will be sticky. I also used clamps to create the mold and make sure there's no void between black and orange sides.

I waited four days to let the silicone to cure. On the fourth day, I removed the molds and the human-like hand was born (show in image 4).

Because it was too sticky, I put a black glove on it, which I regrated afterwards. It doesn't look that cool anymore although it touches and functions like a real human hand.

One last step is to glue the hand onto the wrist part.

This project was an opportunity given to me by Ms. Berbawy. All the engineering skills I learned throughout my project were all new for me at the beginning. Because of this class, Principle of Engineering, I was able to learn a lot of new skills. I put a lot of time revising my design on Fusion 360, and made many test prints. But every time I made mistake, I learned something. And because of that, I got used to the equipment. Gaining the skills for engineering means a lot for me since I want to become an engineer in the future.