Metal Additive Manufacturing Processes
Three Major Processes for Metal 3D Printing
Powder Bed Fusion (PBF)
The PBF process uses a laser or an electron beam to selectively melt areas of a metal powder bed. With each complete pass of the energy source over the powder bed, the build plate is lowered and more material is added until the finished component is complete and removed from the remaining unsolidified powder feedstock. This process uses a small weld pool, has very rapid solidification and high resolution of part features.
Binder Jet is a powder bed process, where a binder is used to selectively print the desired part shape by adhesively joining the metal particles. After the jetting process, the green part is sintered in a furnace to burn off the binder. Then an infiltrant, typically bronze, is melted and drawn into the part to fill in the spaces of the sintered metal powder skeleton to create a fully dense component. The resulting part properties are determined by the interaction of the metal powder and the infiltrant.
Freeform Direct Laser Deposition (FDLD)
In FDLD, parts are built by fusing together metal powders with a laser. The metal powders are injected by a nozzle directly into the melt pool created by the laser. This process uses larger powders, and so is faster but has lower feature resolution. FDLD also lends itself to building parts with gradient properties, as more than one powder feedstock material can be used throughout the build.
Image courtesy of Connecticut Center for Advanced Technology