In article ,
says...
On 05 Oct 2003 09:18:30 GMT, ( Doug Goncz ) wrote:
From: Gary Coffman
Newsgroups: rec.crafts.metalworking

You're implicitly assuming that to replicate a part you need an identical
part on hand as a template. But that's not a requirement. All you really
need is a print.

Of course all you need is a non-self-replicating print, and a
non-self-replicating filing cabinet to keep it in. Do you want to use the lathe
to build a paper mill so you can make the print, and the mill to build a sheet
metal shear so you can file the print, or do you wan't to simplify, simplify,
without cheating.

A print is no more non-self-replicating than a machine tool. Both need
human intervention and stock in order to be replicated. At least the print
only needs a pencil and tracing paper, while your scheme requires a
whole other machine tool being used as nothing more than a template.
The mass penalty difference should be obvious.


Also consider, a proper print conveys information not
inherent in an actual part, tolerances being the most
obvious example. You could argue that this information can
be inferred from the context of the part's use, but this
puts the machinist in the position of properly interpreting
the designer's intent and requires that he have access to
all the information originally available to the designer.

A print will also not include spurious information. The
part to be reproduced may have features that were necessary
or convenient only for the production of the original. For
example, a print may include a note to the effect, "TOOLING
HOLE PERMISSIBLE". But if the part is to be produced by
replication, once that hole is put in one part, every
subsequent generation will have it as well, even though it
has no functional purpose.

Perhaps some sort of "mechanical selection" is required to
get rid of vestigial features g.

Ned Simmons