The weapons factory in the den

Openly available 3-D printer files include plans for manufacturing weaponry. Guns still kill people, and aspects of the burgeoning crowd sourcing movement are making them newly available. Most off the-shelf printers use plastic extrusion, printing material in 2-D layers stacked atop one another; others use stereolithography, an optical fabrication technique with higher resolution than plastic extrusion. Stereolithography means smoother parts ideal for elaborate devices like firearms. Just as the right to bear arms has come under fire, the reality of 3-D-printed guns has raised new questions. Not only about the practical issues underlying the making of guns, but also about the legal repercussions, the institutionalization of social values and standards, and the role of the new hybrids in their midst.