A Marine calibrates a three-dimensional printer during the 3-D Printing Training Course at Marine Corps Base Camp Lejeune, North Carolina. Marines have been embracing 3-D printing for several years now, and there are more than 40 units using 3-D printers in the field to build drones, buildings, vehicles and other items out of various materials. (U.S. Marine Corps photo by Sgt. Ian Leones) - A Marine calibrates a three-dimensional printer during the 3-D Printing Training Course at Marine Corps Base Camp Lejeune, North Carolina. Marines have been embracing 3-D printing for several years now, and there are more than 40 units using 3-D printers in the field to build drones, buildings, vehicles and other items out of various materials. (U.S. Marine Corps photo by Sgt. Ian Leones)