The possibility of implementing Feynman's proposal for achieving ultraminiaturization by an iterative process of 3D machines making even-smaller 3D machines is considered in the nature of a `thought experiment.' A large array of Stewart platform machines is proposed as the `machine/factory' which possibly could have the capability to make ever-smaller versions of itself.
E. Clayton Teague,
"1/N Feynman machines as a path to ultraminiaturization", Proc. SPIE 2640, Microlithography and Metrology in Micromachining, (26 September 1995); doi: 10.1117/12.222635; https://doi.org/10.1117/12.222635