RepRap Blog: Metal Bits from a RepRap
Vik Olliver, a RepRap hobbyist, created a PLA mold (of a Mighty RepRap Power Ring), filled it with melted pewter, let it cool, then used a hammer to chip off the PLA material. This is the first use of RepRap with metal casting that I'm aware of. In his blog post on the topic, Olliver implies that it might be possible to try it with metals with higher melting points like aluminum or bronze, with proper research. Here is a photograph of the completed ring:
Also check out Thingiverse, which has plans for various designs for RepRap to fabricate. I really like the planetary gear calling card and Turner's cube.
Plaster of Paris (which was used to shield the PLA from the heat of the melted pewter) has a melting point of 2660 °F (1460 °C), but according to Olliver, using metals like molten aluminum, with a temperature of 1220 °F (660 °C) or greater can "cause plaster of Paris to decompose in undesirable ways and you need to research it properly."
For aluminum and bronze, you'd need investment, a type of plaster used by jewelers. According to the Plaster FAQ, it "will hang together just enough, after being brought to more than 1000 degrees F, to hold molten bronze and impart shape and fine detail, while still being friable enough to remove easily from the casting." For even higher temperatures, ceramic shells must be used.
December 5th, 2009 - 16:57
Von Neumann self replicating universal constructors are slowly being realized with different methods. 3-D printers are another interesting technology. I always found the development of small spherical microchips by this company to be interesting:
http://www.ballsemi.com/
Molecular manufacturing is simply the limit of the most powerful universal constructor realizable. It will be interesting to see if RepRap, or something like it, becomes a widestpread “universal” constructor technology, before the development of molecular manufacturing.
Great post Michael.