3D Printable Prosthetic Hand

Hello! This was my senior project and I wanted to share the design for anyone to be able to use. This device is meant to assist people missing any amount of fingers. Note: This device is only a prototype and should only be used for recreational use. These instructions are only meant to accompany the video above. PLEASE read the instructions and watch the video. Files are listed below

3D Prints Required

• 1 Wrist
• 1 Hand
• 5 NEWFINGERs

Materials (Amazon page linked)

• 1.5 in Velcro Tape
• Fishing Line
• 1mm Elastic Cord
• Two 1/4 in by 2 in FULLY THREADED bolts.
• One 1/4 in by 1 in bolt.
• One 1/4 in by 4.5 in bolt. Does not need to be fully threaded.

NOTE: For all bolts, head type doesn't matter; however, a Phillips head may be easiest.

Cut two pieces of around 1 ft each. Run the velcro through the hand and the wrist, then attach velcro of the other kind to one side of the velcro so it can attach. Should create a loop. In the video, I show two different methods of attachment for the velcro. I would recommend doing it the way I show.

Slide the 4.5 in. bolt down the wrist and the hand while they are flush. Attach the other side via nut and optional washer.

This is the most crucial step for making the prosthetic work.

1. Cut a very long piece of fishing line. I would say 3 feet to be safe
2. Flame each end of the string so it becomes a little ball. This will make it much easier to thread through.
3. Thread it through the bottom of the fingers (the underside of the curve). It should curve around at the most distal part and be threaded back through. (See video) By the end of threading it through, there should be two ends of string sticking out.
4. Run these through the hole on the front bottom of the hand. This is not easy to do because the "tunnel" is l shaped. Take a pair of tweezers or something similar to thread it through. Pull the string all the way through.

Once you get the string through, attach the finger to the hand with the 2 in bolts. The nut will go in the middle as seen in the video. For the thumb, use the 1 in bolt. You may need to screw these in to get them to go in.

1. Cut around 2 feet long string of elastic cord
2. Lace the string through the finger. It is similar to the fishing line, except the holes are on top and go all the way to the tip of the finger
3. Lace the string through the tie box nearest to the finger
4. Tie the elastic string. It should be tight enough to where the finger will shoot back up after being pressed down, but not so tight that the finger is impossible to close. (In the video, I do it slightly too tight)

1. Thread it through the first box on the hand. There are 5 slots for 5 sets of string. Thread it through the closest hole.
2. Now put it through the second box on the wrist. There are 6 slots for 5 sets of string, but there are 5 points to tie. One side of the string goes through one hole and the other goes through the other. (There will be 2 strings in each hole once completed, except for the holes on the end).
3. You will need another person to help you with this next step.
4. Bend the wrist down anywhere between 60 to 90 degrees. Hold the finger down so it closes all the way down. One person will need to hold the hand in this position and resist the tension created by the other person. Don't let the hand change in shape.
5. The other person will now tie a TIGHT knot with the fishing line. Tie it four times to make sure it does not come unknotted.
6. Optionally, hot glue the knot. This should keep it from coming untied.

Finally, repeat steps 3-6 for all of the fingers.