Apple software engineer Nirav Patel wanted to create something useful with his 3D printer, so he designed a system that generates any key from any lock from any manufacturer using just the lock code. Lol, what?
Using a specialised CAD program and the manufacturers' various pin depth specifications, he was able to generate functioning keys for the two most common American cylinder types, the Kwikset KW1 and the Schlage SC1.
To make a key, Patel first fashions an appropriate-sized blank, then generates a model of the key in a specialised CAD program using the manufacturer's lock code to determine the correct bitting and then hits Print. Plans and models are posted on his site and free to distribute.