You might not realize it, but there are actually two companies pursuing asteroid mining today. One is Planetary Resources, backed by notables such as James Cameron, Larry Page, Eric Schmidt and more. The other company is Deep Space Industries.
And they're making a space-based 3D printer.
Their purpose is to seek out asteroids containing suitable quantities of metals and water. They wish to convert these raw materials into usable space products on site and thus save on the massive cost of shipping heavy metal parts into deep space.
They'll accomplish this with the "MicroGravity Foundry", pictured above. The first version, the MGF-3, is a rack mounted affair, but the successor, the MGF-4, is designed to build and assemble very large structures such as solar power arrays and communications antennae. They say:
Deep Space is building a team with the skills to turn raw asteroids into valuable products. We'll serve in-space markets first, where fuel and materials shipped up from Earth are exceedingly costly. The MicroGravity Foundry will be able to transform asteroid ore into complex metal parts with a simple 3D printing process. Deep Space will be the Maker of things that are needed to open the frontier of space, using processes and machines that start small and be scaled as large as our plans take us.
We're really in the 21st century, aren't we?