Our visit to Shapeways Factory of the Future revealed a fascinating technique they use to produce your objects. You might assume they take your order and then simply print it on one of their big machines. This is hardly the case, as they have to ensure the most efficient use of those big boys in the back room.
Their goal is to run the printers flat out with a build chamber completely full of objects. They do this by mixing everyone's objects together in a print operation. They carefully "Tetris" dozens or even hundreds of objects together in the build volume, much like you'd see attendants parking cars on a ferry. There is very little space between the objects.
The big machines print their entire build chamber full of these objects, resulting in a massive "cake" of powder containing all the objects.
This is where the challenge arises: how to sort out which objects belong to which order?
Shapeways has solved this by intricately mapping out the contents of each cake. We observed many printed (on paper) maps of these cakes, which Shapeways personnel use to dig objects out of the powder. Sometimes for a collection of very tiny objects they'll actually add a 3D printed "cage" around them so as to not lose the small parts.
Is this a technique home 3D print operators could use? Not really, as you'd need a powder-based 3D printer to take full advantage of it.
But we're hoping that's going to happen soon.