Air System / Ventilation - Check Valve / Flap for 100mm / 4inch

Another thing that came out of my ventilation system for my 3d printer setup. I needed a check valve that prevents air from the outside to come in while letting air be pushed through from the inside. I tested some off the shelf stuff but could not find a flap that opened up on low air pressure.

I attached two springs, the normal one opens up on higher air pressure, the smaller one (the one called “Feder neu dünn” opens up on low pressure. Check the video below to see how to fold the spring to make all of this work.

You will need a M3x10 screw and nuts to secure everything. Print the flap and the inner ring in PETG, the outer rings can be printed with PLA for example. Print the flap with supports on the hinges.

You can find a demo here: