--- In STMFC@..., timboconnor@... wrote:

Dennis

I agree with you that custom parts are going to cost more, because of
the small scale of production. But what of it? We are there already.

It's

not a trend to comtemplate for the future.

Thanks to the recent release of new HO scale intermodal flats I would
expect a demand to develop for more accurate hitches to match each of
the prototypes. This will be a limited demand and limited production --
but that is why "3-D printing" and similar technologies are interesting.
(Sorry for the non-STMFC example I'm sure people can think of examples
for steam era freight cars.)

I think the discussion has tended to compare the "one-of" items with
mass production -- obviously investment production (using whatever
methods) is going to be cheaper, but it also has to have high volumes
to get a return on the investment.

Tim O'Connor

Tim,

Which brings us a full circle to the original discussion of
"do-it-yourself" 3-D printing. I now finally have available the images
I need to make my point that it's not quite ready for prime time yet.

Jim King was nice enough to give us a quite detailed rundown of the
current state of the art that he has used recently to produce masters
for his Smokey Valley resin kits. As far as I can tell, he is using an
experienced firm equipped with the absolute best equipment available
today. Several people have posted photos or links to photos of Jim's
Southern gondola; this one likely best illustrates the quality of
these kits:

<http://ph.groups.yahoo.com/group/STMFC/photos/view/dbdd?b=3&o=2>

The one thing that has been overlooked here is that that quality is
not due solely to the capabilities of the state-of-the-art SLA system;
the ultimate quality of the part finish is due to Jim's skill as a
polisher / finisher. This photo of one of Jim's CofGa car masters,
provided by Tom Madden, shows what those ends looked like when they
came off the mega thousand dollar equipment:

<http://ph.groups.yahoo.com/group/STMFC/photos/view/dbdd?b=1&o=2>

Note the "wedding cake" effect at the ends of the ribs, most
noticeable at the right end due to the lighting, but actually present
all the way around. This is the Achilles heel of the process; the
part is built in layers, and anywhere the finished part surface
doesn't lay in the same plane as the layers, the terraces result.

Using these parts as patterns, one can afford to expend whatever time
it takes to work these ridges out of the part. However, to use an RP
machine as a production machine, one must spend all that time
reworking the curved surfaces of each and every part, or just live
with them. Since, as Jim pointed out, you are going to be paying a
minimum of $150 to have this part set up to run (or you won't be
getting anywhere near this quality from the DIY machine in the Times
article), I'm not sure that anyone would think these parts are worth
that amount of money if they still needed extensive work. The only way
to make this technology useful, at this point in time, is to consider
these as a first step toward some really nice patterns, do the work to
finish the surfaces, then have production run by some other method.

A really cool technology? Yes, it is. But it's not Mr. Spock's
replicater quite yet.

Dennis





Yahoo! Groups Links