Print me a jet engine
economist.com
economist.com
You're right - it's going to be very difficult to get high tolerance parts using any method of 3D Printing. Don't say never - but isn't not as close of the koolaid machine would have you believe.
The result is definitely not crystalline, in fact it is better compared with regular sintered materials.
They are most likely printing things that 1) don't move, and 2) aren't subjected to any type of stress or heat.
I can't imagine that you can print something layer by layer with fused powder and expect to make anything as solid and tolerant as the normal (crystal) growth and/or casting/molding/etc processes make.
Additionally, many aerospace parts (F22 air vents, for example) are produced in a similar fashion. There are a series of Google Tech Talks on the subject [2]. In short, complicated shapes can be produced with less waste (versus milling from a larger block of material), greater tolerances (no warpage from welding heat, curing of glue), less labor (no assembly jigs), and usually less mass (due to partial infilling of material cross section).
Lastly, you'd be surprised at the number of molds that are now being made via '3d printing' (I'm growing to hate this term) for composite applications. Normally they are CNC'd from aluminum (or 'tooling gel') - whereas smaller run items can be laser sintered. My startup uses PLA molds for vacuum infused carbon composites which we print from a RepRap Mendelmax. (router enclosures, antenna mounts, UAV and motosports stuff, etc).
[1] http://www.engadget.com/2012/11/09/nasa-building-space-launc...
Usually they are simply cast and then reworked, which produces a blade of lesser quality than the single crystal ones but they are still quite usable (and a lot cheaper!).
This article does illustrate the different methods of 3D or additive printing capabilities, outside of the common knowledge we seem to be exposed to through the maker movement. NASA / Military has also explored a multitude of options with additive printing, battle field printing and space station printing.
In regards to parts such as fan blades, which are mainly composite materials in recent engines, this would not be applicable. Where there are parts that are subject to extreme heat and must retain certain properties, therefore, expensive to manufacture, this process has many benefits as highlighted.
EDIT: In the case of "extreme heat", it may apply for certain types of metals.
http://machinedesign.com/article/new-superalloys-boost-direc...
http://www.onlineamd.com/amd-0310-laser-sintered-titanium-eo...
sudo print me a jet engine
sudo: can't open /private/IP/license/jet-engine: Permission denied.
sudo: no valid Intellectual Property license on file to print object.
sudo: contacting authorities, reporting potential IP violation attempt.
sudo: locking down local system to preserve evidence... [done]
sudo: quitting. have a nice day.
It will scale, eventually. I guess as soon as someone gets serious about the reproducible nano-compositor/decompositor style of printnozzle..