The Printer That Prints Itself - Can you see what it is yet?
(Page 3 of 4 )
The RepRap in operation is unremarkable, but strangely fascinating. Painfully slowly, it lays down layer after layer of molten plastic, creating an effect something like watching Rolf Harris in that old kids TV show. Rolf would paint a cartoon a little at a time, looking up at the camera occasionally to ask "Can you see what it is yet?" You never could, of course, until he'd finished. However, it's hard to avoid a slight sense of anticlimax when, after hours of painstaking progress, the extrusion head finally stops and you are left looking at a small, white, plastic thing, unremarkable in just about every respect except for the fact that it was made from scratch on a machine that cost no more than a desktop laser printer.
There are currently three RepRap prototype models, whose idiosyncratic names give an insight into the preoccupations of the team's members. Zaphod, unsurprisingly, is the one with two heads, both of which are static. The bed on which the work piece is mounted moves during printing to allow the required shape to be built up. Zaphod is a fully functional prototype, and has been used by the team for testing design concepts and software. It has successfully made the parts for a working second generation extruder.
Tommelise occupies considerably more space than Zaphod. Built in prototype from milled timber and looking like a child's wood-block toy, it bears little resemblance to its sci-fi siblings. This homespun look conceals a high degree of sophistication; unlike the other models, Tommelise utilizes a triple-axis head driven by cheap and efficient pseudostepper motors. These in turn are controlled by a powerful PIC micro-controller which also manages the extruder.
Darwin, the most developed of the prototypes, is different again. Constructed from rods held together by large numbers of chunky plastic brackets, it's easy to see how this would be the most obviously self-replicating. It also has something of a child's toy look about it; in this case it's more meccano than maple, but with an unexpected and deceptive fragility to its appearance.
Bowyer likens the machine's self-replicating abilities to Darwinian evolution, and specifically to viruses which replicate their own component parts but are dependent on biological hosts such as ourselves for their assembly. In the same way, the RepRap can replicate the majority of its components at low cost but needs human intervention to assemble them into a working device.
To Bowyer's frustration, however, there are some parts that it can't yet make for itself. The machine is dependent on a number of metal components such as machine screws, bushes and motors, and is also incapable of producing its own electronics and lubricants. Bowyer anticipates that RepRap v2.0, codenamed Mendel, will incorporate a print head capable of printing conductive material, enabling it to create its own circuitry. More speculatively, he hopes that later versions will expand the range of printable materials to include metals, wax and ceramics, enabling the project to get much closer to its goal of 100% self-replicability.
Next: The end for the patent? >>
More Peripherals Articles
More By Bruce Coker
