So I just noticed that you can print things in Porcelain that are too big (max bounding box size) to bring in Castable wax. Why is that? I thought this was rather odd seeing as how I understood it, the Porcelain prints go through a wax casting process. Ultimately I'm looking to print a wax cast of a mug to try and have it produced on a more economic scale than what 3D printing it at Shapeways would allow.
Misunderstanding - the brass, bronze and silver go through a lost wax casting process. The porcelain is slipcast using a mold made from "strong&flexible" nylon that is designed around the uploaded model.
Either way, the big issue is strength of the final item. It's likely that a large item in wax would not survive shipping, but the same item in porcelain would be much much stronger.
Any tips on how I could learn to do the Slipcasting myself? I can't afford to prototype with the new porcelain prices but the SWF costs are still within my budget.
Ask a local potter or ceramics artist if at all possible, or trawl youtube for instructional videos. In all likelyhood you will have to build a standard plaster mold around your printed object - for SWF molds you would probably need a special clay formulation. And undercuts are going to be a problem if you want to do several casts from the same mold (but probably even if you intend to destroy each mold to get at the part, as shapeways probably does).See e.g. http://www.lagunaclay.com/support/art-of-ceramicmoldmaking.php or http://www.pottersfriend.co.uk/p.php?page=Moulds for a quick rundown of the moldmaking (though a mug will be more ambitious than the solid figurine used in the first example). Some ceramics suppliers also sell readymade molds for porcelain bells, angels etc. to let you try your hand at just the slipcasting itself first.