Thinking about 3-D printing, it might be best just to think about it in terms of
a machine like a CNC 5-axis mill.. It can machine out and create amazingly
intricate parts, it takes a huge amount of technical expertise to run one
properly, it's rather expensive, and the output is relatively slow. It's perfect
for doing products that are expensive or don't have to be mass-produced. If you
need mass-production, (for metal) it's better to stamp out parts and form them
in a secondary process..