ExtremeTech profiles the stunning advances in 3D printing metal, such as NASA 3D printing steel parts for use in space with the goal of being able to do in space.
The real breakthrough that has enabled 3D printing for the masses has been the laser. Spray welding is a technique that has been used for decades to build up worn motor shafts, but it is far too crude for controlled additive printing. Spray welding uses a gravity-fed powdered metal dispenser integrated into a special oxygen-acetylene torch head which melts the powder as it is dispensed. Swapping the torch for a laser gave us the powerful construction tool we have today.