Not all 3d printers require a lye bath - just the high end ones that allow for support material
I own two that are more hobbyist grade that are much smaller than the Dimension printers - started out a few years with a Makerbot Cupcake, and now I've upgraded to the new Solidoodle 2 (
http://www.solidoodle.com/).
Both of my printers have a single ABS extruder. Even being that primitive, they do a surprisingly good job; you can get up to about a 60 degree overhang angle without support material. The printing process is really low fuss - heat the printer to 200 degrees celsius and the build platform to 100 degrees, and then let it do its thing extruding.
Back to the OP's premise, honestly, I find the possibility of a 3D printer producing weapon components airside to be laughable:
- The parts, while sturdy, do have grain from the additive extrusion process. To make a firearm, you'd probably want to do additional machining to ensure they all fit together correctly.
- The build table on my printer is about 6"x6"x6". People do travel with printers my size (
http://www.makerbot.com/blog/2010/04...th-a-makerbot/), but the 6" square build envelope isn't super flexible. Making any bigger parts would require a printer that would be much larger than carryon luggage requirements (and therefore wouldn't fit through the xray.)
- These things are SLOW. Slow slow slow. I printed a phone dock (
http://www.thingiverse.com/thing:15805) and it turned out great, but it also took three hours of extrusion. If you're printing a gun part, you're going to be sitting there watching it excrutiatingly deposit each layer one by one.
- 3D printers are neat. They attract a crowd - everyone loves to watch them print. Someone's going to notice you loading up "gun-lower-body.gcode" on your laptop, and they're going to wonder why something that looks suspiciously gun-like is slowly being created by your printer.
- ABS is very much not heat resistant - that's the whole premise about how these things work. You'd need to supplement the plastic parts with metal ones - there's a reason plastic guns aren't commonplace
I love my 3D printer and it's both a great hobby tool and a great conversation piece...... but it's not an effective weapons factory. There are much, much, much easier threats than manufacturing weapon components airside. :P