Wow, that’s a big 3d printer! (If you’ve ever printed spaghetti on a smaller 3d printer then you know)

The sheath deals with that. Friction/screw tension makes it harder too. You’re right though, there is no lock to keep it closed if it’s not enclosed somehow.

You can change quite a lot (pivot & blade are original)

That’s the speed of lightning in a vacuum, the speed of lightning in a dojo is significantly slower. In fact scientists believe that it can be brought to a crawl visible to normal human vision using a Tai Chi doping process. (Vacuum: Yes, i know)