A mechanism that works at scale X doesn't necessarily work at scale Y.

Different forces and material properties are all at relatively different levels.

The one I know offhand that will mess with stuff is the square-cube law. If you double the linear dimensions of something, it's twice as big, linearly, but 4 times the surface area and 8 times as heavy. The strength of anything that depends on area (like friction) won't scale at the same rate as anything that depends on mass or volume or anything.

Not to mention I'm sure this thing can only print a few different materials. Unless those are also _all_ of the materials it's made out of, it couldn't even make itself.