At a height of about two stories high, this may be the world's largest metal 3D printer. At Northwestern Polytechnical University (NPU) in Xi'an, professor Huang Weidong (second from left) has ... more 
At a height of about two stories high, this may be the world's largest metal 3D printer. At Northwestern Polytechnical University (NPU) in Xi'an, professor Huang Weidong (second from left) has successfully printed precisely shaped titanium airp less 
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LiveScience.com | Photo By Hod Lipson
Fri, Jul 19, 2013 4:25 PM EDT