Proliferation of cheap 3-D printers raises security concerns.

* When a man in May demonstrated that he could build a plastic gun from a 3-D printer and fire at least one shot from the homemade device, the story sent off alarm bells on Capitol Hill.

Such a weapon could be used to thwart metal detectors designed to keep weapons out of certain facilities, it was postulated.

While the technology to create items made of plastic, ceramics or other materials in a desktop-sized machine has been around for decades, lower prices have brought them into the consumer market. A 3-D printer can be bought for as little as $1,600, which is in the price range of hobbyists, do-it-yourself types and those who like to invent things in their garages.

"Banning a technology, which is your typical standard and knee-jerk reaction when something comes up, does not work," said Michael Hopmeier, president of Unconventional Concepts Inc., a consulting firm specializing in counterterrorism, preparedness response and national security.

Three-D printing is rapidly proliferating throughout the world, experts said at a Center for Science, Technology and Security Policy panel discussion.

But it is only a small part of the larger, advanced additive manufacturing movement, which is using cutting edge computing, materials and equipment to change the way goods are made. The printers are being used to rapidly make prototypes or models.

As for the plastic gun threat, improvised and non-metallic firearms have been around a long time. The prospect of 3-D printed guns gets Congress "excited," but it doesn't change the security landscape in any way, Hopmeier said.

Similarly, a part to convert an AR-15 assault weapon from semiautomatic to fully automatic can be done using 3-D printing. A person can make it from plastic, build a mold around it and pour the metal. That's not unique, Hopmeier noted. It can be done with a mill and a lathe and basic machining skills as well. Three-D printing just lowers the barrier to doing the work "a little bit," he said.

More nefariously, advanced additive manufacturing and 3-D printers could be used to design and make precise, high-sped centrifuges to separate uranium compounds for nuclear weapons, he said. Again, it is not as if this can't be done by other means, advanced manufacturing only lowers the barriers to entry to allow that to be done, Hopmeier said.

"It doesn't...