More than 50 years ago, computer pioneer John von Neumann conceived of a self-reproducing machine. It would mine its own ore, smelt it into metal ingots, machine the ingots into parts, and assemble the parts into a copy of itself. During the 1980s, nanotechnology evangelists worked out the same idea on a much smaller scale, prompting critics to envision a horror scenario in which molecule-size bots reduce the entire world to a featureless mass dubbed ”gray goo.”
Today there’s RepRap. Unlike gray goo or von Neumann’s idealized machines, RepRap (short for ”replicating rapid-prototyper”) doesn’t harvest its own materials. But also unlike them, it’s entirely real. For about US $725 in parts, this self-reproducing machine, spawned by a global band of engineers and hobbyists, will squirt out complex three-dimensional patterns of molten plastic filaments that will solidify into most, if not all, of the mechanical parts for another RepRap (see sidebar, ”Self-Reproduction Is Hard; Selfâ¿¿Assembly Is Harder”).
RepRap consists of a roughly cubical half-meter frame enclosing its fabrication volume, along with motors, drive electronics, and one or more ”write heads” that extrude plastic (or some other material) into the desired shapes.
RepRap gets its instructions from your PC, via a USB connection. Software on the PC, written in Java, takes design files produced by 3-D drawing programs and turns them into instructions for the RepRap. The software converts solid-object models into a series of movements with the extruder on or off, and with either sparse or solid interior filling, depending on a part’s structural requirements.
Because all of RepRap’s software and hardware designs are open source, no one knows exactly how many people are using it on projects. Adrian Bowyer, a senior lecturer in mechanical engineering at the University of Bath, in England, and the originator of the project, recalls the day last winter when a RepRap machine appeared on exhibit at the Science Museum in London. He had never even heard from the team building it, much less known of their plans to put one on display.
Zach Smith, who manages the RepRap Research Foundation (http://www.rrrf.org), in New York City, counts a dozen or so core developers, but about 500 more have bought parts from the foundation’s online store. Some of the circuit boards and other components can’t be purchased elsewhere, he notes, although a determined builder could fabricate them from scratch.
I’m fascinated not only by the idea of RepRap but also by the possibility of building one. I already have some ideas that would extend RepRap’s ability to create different forms—for example, how to implement some of the rough designs others have floated for additional assembly heads that pick up and place components or wield cutters that in turn would cut parts from materials that can’t be extruded.
But for me, RepRap’s biggest appeal is its appetite for prefabricated circuit boards that I don’t have to etch or solder and for structural components that call for a minimum of epoxying or lathe work. In other words, even if I build it, this thing might actually work.
You’ll be reading more about my attempts to build a self-reproducing machine. And if you’re working on a RepRap, I would very much like to hear from you.
About the Author
PAUL WALLICH has built half a dozen computers in his lifetime. His most recent contraption is RepRap, a self-replicating machine, which he wrote about for Hands On [p. 24]. Despite his love of making machines, Wallich says he’s ”mostly a writer who builds stuff, not an engineer or builder.” His work has also appeared in Scientific American and Popular Science .