Comment by kadoban
19 hours ago
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.
whats the practical impact of this law? regarding friction there is probably the screws that need to be fixated with a glue?
There are many. At larger scales, weight and inertia dominate, but also magnetic fields matter much more than static electrical fields for generating force. At smaller scales viscosity, friction, and surface tension dominate, and electrostatics are much better at producing forces. Small-scale structures are often much 'stronger' than you would intuitively think (if you've heard the fact that ants can lift 50x their body weight, the square-cube law is why. A dog-sized ant would not be able to lift a car, or even breathe).
For this specifically, you would be looking at a radically different structural design, probably entirely flexural and without using traditional magnetic motors. Look at how MEMS design works in practice for an idea (though MEMS also tends to be constrained by current manufacturing techniques which push everything to be very planar).