To reduce the use of adhesive and hardware such as nuts, bolts, screws and washers, our D&M team decided to implement the idea of press fitting in our assembly. Press fit is a mechanical fastening between two parts which is achieved by friction after the parts pushed together.

Limbi’s D&M team designed and printed test prototype for our press fit parts to be used in our brace design and docking mechanism layers.

We tested three different extrude and hole pairs:

*length of extrusion and cut are the same: 0.5 inches

1. 0.15 in diameter extrusion and 0.16 in diameter cut (0.01 inch difference in diameter).
2. 0.15 in diameter extrusion and 0.175 in diameter cut (0.025 inch difference in diameter).
3. 0.15 in diameter extrusion and 0.2 in diameter cut (0.05 inch difference in diameter).

Results:

-0.01 in difference is too tight extruded parts would not even fit in the holes.

For he two other extrusion and cut pairs, gravity test is performed: mated parts are held upside down where the friction is the only force holding the male part.

-0.05 in difference is loose which cause the part to fall off.

-0.025 in difference is just the right fit that held the male part from falling during the gravity test. Also, it still allows for the pair to detach.