Assuming for the sake of argument that a 3D printer can replicate all of its own parts, it still requires human labor to put those parts together into another 3D printer. By contrast, Drexler assumes that the parts in his nanomachines would just automatically self-assemble to minimize potential energy, like the self-assembly of biological molecules in aqueous solutions. Seems like the difference matters to me.
BTW, Locklin weighs in on the alleged printed firearm receiver a few months back:
Nerds have this fantasy that solid printers will make them infinite open-source useful objects in … the future. This is the sheerest fantasy; a fantasy that can only be held by people who have never made a useful mechanical object in the workshop. Solid printers can make crude unassembled plastic parts; nothing else. No electronics can be made in this way. No assembled parts can be made in this way. Even if a home printer could print things of metal (this will never happen on a cheap home use basis as you need a very high power laser to melt metal powders), it will effectively be sintered metal, or sintered plastic-metal composites. That’s not the same thing as a machined piece of solid metal. It doesn’t have the same mechanical properties, and barring some preposterous breakthrough, it never will. Some parts will not ever be realizable with this sort of technology: for things like, say, a plastic simulacrum of a rifle barrel within linear tolerances, you’ll always need specialized machine tools.
a 3D printer can replicate all of its own parts, it still requires human labor to put those parts together
into another 3D printer
Certainly. A true macroscopic replicator would also require robotic parts capable of assembling both the printer and the robotic parts, and a printer capable of printing printer parts as well as robotic parts.
Drexler assumes that the parts in his nanomachines would just automatically self-assemble to
minimize potential energy
I grant that this seems implausible, especially for non-biological “mechanical” parts.
Assuming for the sake of argument that a 3D printer can replicate all of its own parts, it still requires human labor to put those parts together into another 3D printer. By contrast, Drexler assumes that the parts in his nanomachines would just automatically self-assemble to minimize potential energy, like the self-assembly of biological molecules in aqueous solutions. Seems like the difference matters to me.
BTW, Locklin weighs in on the alleged printed firearm receiver a few months back:
http://scottlocklin.wordpress.com/2012/08/11/bad-engineering-journalism-reporting-on-3-d-printing-of-guns/
Certainly. A true macroscopic replicator would also require robotic parts capable of assembling both the printer and the robotic parts, and a printer capable of printing printer parts as well as robotic parts.
I grant that this seems implausible, especially for non-biological “mechanical” parts.