The first key to thinking about 3-D printers is this: Do not think printer. Think magic box that creates any object you can imagine.
In the box, razor-thin layers of powdered material (acrylic, nylon, silver, whatever) pile one on top of the other, and then, voila — you've got a shoe, or a cup, or a ring, or an iPhone case.
It's miraculous to see. Press a button, make anything you want. But just how important is 3-D printing? Unlike earlier big-deal technologies (like, say, the tractor) 3-D printing won't really replace what came before.
"If you're producing trash cans or stadium seats, you'll more than likely produce them the old way," says analyst Terry Wohlers.
And for consumers, the economist Tyler Cowen points out, it's still way easier to order something from Amazon than print it yourself — and that's how people will buy things for the foreseeable future.
Still, 3-D printing is amazingly powerful for personalized applications.
Right now, there are 30,000 people walking around with 3-D printed titanium hips, which are less expensive than conventionally manufactured artificial hips.
Boosters of 3-D printing dream of a day when printers can make new body parts. More prosaically, they talk about a day when every shirt, every dress, every pair of pants can be custom printed to perfectly fit each person.
Another thing to keep in mind about 3-D printing: It democratizes who gets to be in the manufacturing business. You don't need a giant factory and million-dollar machines. You just need $500 and a garage.