From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Thu Jul 13 2000 - 17:17:42 MDT
On Thu, 13 Jul 2000, Steven K. Graham wrote:
Hi Steve & welcome,
> Has anyone ever tried to build a machine which could take a lego object,
> and build a copy? Or duplicate an object in any similarly constrained
> design/manufacturing environment?
There are "rough" matter compilers that exist today under the heading
of "rapid prototyping" machines. They basically use lasers to photo-cure
a light sensitive plastic in the exact shape/form of the part you need.
There are also 3D scanners that can read the shape of an object and
drive the laser. So replicating at least the size and shape of something
like a lego can be done now. It only works for plastic parts though which
limits the applications.
The problem is to get it to be self-bootstrapping -- i.e. you would like
the read & write machinery to be constructed entirely out of components
that could be manufactured using the read and write machinery. That
currently is not the case (lasers and computers for the most part are
not made out of plastic).
I've discussed this with Robert Freitas regarding the original NASA
study (which he co-authored) involving self-replicating factories on
the moon. The question was --
"Why is nanotech better than self-replicating macro-tech
(e.g. the moon factory)?"
His succinct answer was:
"The parts count is lower."
The problem isn't that self-replicating macro-scale machines
are impossible. The problem is that the design challenges are
formidable because the parts count is so high. (Imagine
designing a milling machine that can produce all the parts
*in* the milling machine). As I've discussed on the list months
ago (see the archives), you also run into the economic problem of
having "factory factory". Given the exponential growth in supply that
may allow, no sane businessperson would view the design of a "factory
factory" as an investment likely to provide a good ROI. (Everyone
who buys your product becomes your competitor.) My conclusion
was that only governments or highly committed groups with large
resources at their disposal could consider the development of
"factory factories".
Hope that answers some of the questions.
Robert
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