Watch out, humans: An invasion of self-replicating Lego robots could be at hand.

Software engineer by day, Lego maniac by night Will Gorman has created the MakerLegoBot, a machine that can take a virtual 3-D model and assemble it using Lego bricks.

The machine is itself built entirely out of the Lego system, which raises the possibility – theoretically at least – that the machine could, with some modifications, build a copy of itself. The 3-D assembler uses three Lego Mindstorms NXT Bricks, along with 9 NXT motors.

"There is a recursiveness to this whole thing," says Gorman.

"I love the idea of self-assembly and the Star Trek replicator and I love Legos," he says. "I wanted to bring those two worlds together.

The MakerLegoBot is a tribute to the emerging trend of 3-D printers and self-replicating machines such as MakerBot and RepRap.

Over the last two years, enthusiastic do-it-yourselfers have embraced 3-D printers that can take blobs of plastic and shape them into objects you desire. DIYers are using Makerbot and RepRap to fabricate iPod docks, plastic bracelets, hair clips and miniature teapots at home. Such devices are helping plant "the seeds of the next industrial revolution," according to Wired magazine editor Chris Anderson.

More mainstream 3-D printers use plastic, not Lego, but the principle of converting 3-D designs into real objects is similar.

Here's how the MakerLegoBot works: A feed system that's about two-and-a-half feet tall and can hold about 35 bricks connects to the LegoBot. The object that the MakerLegoBot is to assemble is designed in MLCad, a modeling program. A Java app that runs on a PC takes the file from the MLCad software, determines a set of print instructions and sends those instructions over USB to the LegoBot.

The machine retrieves a brick from the feed system and places it in the exact location where it should be. It uses an axle-based release mechanism to leave the brick in place.

The current design works with 1x2, 2x2, 3x2, 4x2 and 8x2 Lego bricks. So far, the machine can't print Lego blocks or use NXT blocks and motors – a major limitation. It just works off ordinary Lego bricks, which must be fed into it by human assistants. Of course, a MakerBot might be able to fabricate a Lego brick, raising some interesting possibilities for a collective robot uprising.

For now, system can build objects that are up to 12 bricks tall.

Gorman has posted instructions on how to build the MakerLegoBot on his site.

And as this amazing video shows, the MakerLegoBot goes to work assembling the blocks.

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Photos: Will Gorman