3D Printed Replacement Knob for Arthritis Assistance

Hi, my name is Ryan Co and I currently attend Santa Clara High School.

As my grandparents grow older, they face new physical limitations which prevent them from fixing parts of their house that have broken down. With the recent heat wave, I wanted to check on the quality of their air conditioner and found that one of the knobs was broken. To get around this, my grandpa tried to use a pair of pliers to turn the knob, but with his arthritis, it is hard to grab things.

To help them, I decided to 3D print a new knob that would not only replace the broken one, but allow more leverage to make it easier for my grandpa to turn due to his arthritis.

• PLA filament
• Sandpaper (optional)

To allow the 3D printed knob to fit into the rod of the air conditioner, I needed to mimic the shape of the original knob. After some measuring I figured out the dimensions and began brainstorming different knob shapes. I eventually settled on a long handle that stuck out from behind the knob that offered more leverage by not requiring its user to grab it and rather requiring a simple push to turn.

I first used the measurements from the broken knob to recreate the hole that would allow the knob to fit inside the rod of the air conditioner. After extruding that, I created a simple knob shape at the front to indicate which direction it was pointing and a long end to allow for the leverage. Finally, I create fillets on the edges, resulting in a more polished look without sharp corners.

I printed my design on the Craftbot Plus 3D printer using standard PLA filament. Since the design did not require much precision, I changed the print quality to medium.

After a little bit of sanding, the knob fit tightly into the rod. When testing, I found that the new knob was significantly easier to turn than the original one, making the design a success!