Additive rapid prototyping in plastic materials is becoming quite accessible to home and hobby users. If you’re a hobbyist on a typical budget wanting to rapid prototype in metal, however, you’re limited to subtractive methods, i.e. CNC machine tools like mills and lathes, and even those are not exactly “cheap.” Professional 3D printing services like Shapeways offer additive metal prototyping in metals like stainless steel and gold, but it’s extremely expensive. The technology their 3D printers use, called “laser sintering,” is fundamentally different from the RepRap-type fused-filament (“robot hot glue gun”) 3D printers at the “garage” end of the pricing scale.

In selective laser sintering (SLS), the object is built up in a bed of powder by a scanning laser beam that fuses tiny bits of the powder together, one layer at a time. After each layer of the model is fused, a fresh, thin, uniform sheet of powder is swept over the bed for printing the next layer.

Swarthmore College engineering student Andreas Bastian has developed a low-cost, open-source laser sintering printer design. It uses an IR laser diode on a bed of powder made from a mixture of wax and carbon, and produces fused wax models, which can then be duplicated in metal, for instance aluminum, using a traditional lost-wax casting process. I have written before about a similar process that uses a CNC hot-wire cutter to make Styrofoam models that can then be “metallized” via lost-foam casting, but that, too, is a subtractive process, and limits the possible shapes of the model in ways that the additive SLS process does not. [via Hack a Day]