All Shapeways parts supplied with a shiny finish are finished by a "tumbling" process. The machine is known as a hi energy barrel finisher. Built something like a ferris wheel, this machine has several barrels that that rotate independently, as the central wheel rotates in the opposite direction. This dual action rotation creates an enormous amount of kinetic energy in the form of friction, and allows rapid processing of parts. Each barrel contains a different abrasive media. These media are graded to provide a range of effects from a coarse
cut down to a very high final polish. Parts are cycled through each barrel until the desired effect is obtained. These machines are BIG noisy and expensive but can process hundreds of small parts at one time.
The energy produced by these machines
can destroy fine detail or even break some parts.
This depends on your overall design. The forces at work in the
barrel effect the high points and edges of a design most aggressively so these surfaces wear down more quickly than flat surfaces or depressions. Small thin projections, (like a tail on a mouse) are not likely to survive intact.
Finishing
any small part is tricky business. The SS print media is particularly tricky because when compared to other metals like bronze, aluminum or even simple steel it has an extremely hard surface and is also somewhat brittle. In truth, some parts will always need to be hand finished to achieve desired results.
-G