You probably think I’m talking about 3D movies. Wrong. They probably can be scary, but I haven’t seen one in decades so I really wouldn’t know.

I’m talking about 3D printers. And you probably think they’re some kind of cute laser printer that somehow prints 3D images on paper. Sorry, wrong again. That’s okay. It’s what I thought until I did a little research.

3D printing is also known as “additive manufacturing.” It’s a way of making things by building them a layer at a time. Real thin layers – about 100 micrometers thin.

That sounds like a good thing, so why would it be scary? Today, it isn’t. But the technology is being developed rapidly, and in the not-so distant future, anyone will be able to buy a 3D printer, and will be able to make anything. And I mean, anything.

What sort-of “anything”? Well … I will be able to design, using computer graphics software and pre-programmed templates, a small flying robot. I can arm it with a tiny explosive device. I can program it to find your house, to fly-in through an open window, land on your table and blow you up.

Impossible? Stupid? No, wrong yet again. It will become possible. I find that scary, and the story gets scarier.

Of course, that’s not why 3D printers are being designed and built. By all accounts, they will revolutionize the world in the same way the printing press, the steam engine and the transistor did. They will be used to “print” anything from whole apartment blocks to organs and body parts. Amazing but true.

They will cut manufacturing costs, because there will be no wastage. Only the needed part will be made, in whatever material is desired, from titanium and steel to plastic … even chocolate! No cutting, grinding, sandpapering or finishing needed. No need even to spray, because the coloring can be blended-in to the raw material. Once the blueprint is made, it will just be a case of pressing the “Print” button, and out will pop the finished part.

Ah, but you’re thinking these printers will be like industrial machines – large, heavy and expensive. Well, the Economist describes them as “A factory on your desk.” Currently the smallest is about the size of a milk carton, and the cheapest costs about US$1000. And we’re only at the start of the development process.

So, I’m sure they hold great promise, and maybe I’m something of a Luddite, but the idea of a printer that can produce miniature robots – batteries included, that can produce miniature robots – batteries included, that can produce miniature robots – batteries included… is really quite scary. Especially when there’s no guarantee that the manufacturers will abide by Asimov’s Three Laws of Robotics.