When you think about 3-D printing, chances are you think of little plastic doodads created by desktop devices like those made by MakerBot. Computing and printer giant HP wants you to think about metal. Today the company announced the Metal Jet printer, an industrial-scale 3-D printer that builds items not of plastic but of steel. 3-D plastic printing is widely used for custom items such as prosthetics and hearing aids, and by product designers for prototyping.

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