I know I'm a little late to the party, but I wanted to post these in case they can help people out.
In early April some friends at a 3D printer fab-shop reached out with a request to design an easy-to-mass-produce face mask for healthcare workers and essential personnel. They were printing the La Factoria designs, but the V1 took a long time to print and was too heavy, and the V2 had too many parts and too many potential points of failure. They asked me to design something for them, and this is what I came up with.
I make no guarantees about the safety or effectiveness of these masks, just that I tried my best to make it effective and safe. I'm just an engineer trying to help with the shortage of PPE. Use these at your own risk, and if actual protective equipment is available, use that instead.