Jack

3-D parts are useless for freight car models -- at least for bodies -- the
material lacks hardness and strength. It has to be sandable, drillable, and
cut-able. Tom has the right idea -- make MASTERS in 3-D, modify them as needed
(e.g. adding rivet details), and then make rubber molds from those. The final
models are cast in urethane resin.

Tom had photos of a forthcoming technology that promises to do away with the
hated "scan lines" -- creating completely smooth parts.

The machines at Shapeways and elsewhere cost $100,000 and up. Also, Shapeways
contracts most of their work out -- to over 13,000 different shops.

Most importantly, Shapeways and other shops DO NOT allow you to specify how your
model will be oriented inside the machines. Your parts are batched with many other
parts. This means you have little control over the direction of scan lines, for
example. You can sprue things together to save money for small parts, but to make
an entire freight car (set of masters) sprues will not help you compared to
printing the entire car in 3-D for example. But in Tom's case he was making a
tank car with complex requirements, so he printed parts masters individually.

Tim O'