I present the latest innovation in banana defense technology: the banana switchblade. This single action karambit style switchblade has no practical use as it is just a dull toy but it is a lot of fun to play with. Single action means the blade ejects when the switch is pushed forward. When the switch is pushed back it unlocks the blade but does not retract it. The blade must be manually reset to eject out again.

This design does not require any metal hardware like springs or screws and prints with minimal supports. Instead of springs to lock the blade this design uses printed latches to lock the blade in place. These latches pivot down when not in use meaning they are not under continuous tension. This is important because it allows the design to be made with PLA which permanently deforms under a continuous load. Instead of using screws the parts are pinned in place by 1.75mm filament.

To learn more about how this 3D printed mechanism works I suggest watching the assembly video found below.

Check out the double action version here. Double action means the blade ejects when the switch is pushed forward and retracts when the switch is pushed backwards with no manual reset required.

You can obtain a commercial license to sell prints of this here.

Printing

I suggest printing each part in the orientation show in the print profile. I also suggest printing the tall parts with a brim. The supports are shown in green.

Rubber bands

All the parts are printed except for the rubber bands. The number of rubber bands needed depends on the type of rubber bands used. I like to use four of the rubber bands linked here. You can also follow these link to find specifications about the dimensions of the rubber bands.

Assembly

A video showing how to assemble the toy is linked here.