Metal additive manufacturing is a type of three-dimensional (3D) printing in which metal is joined and solidified to create a 3D object. The ability to produce objects with complex shapes is one of its biggest advantages compared to traditional techniques for metal manufacturing. A computer controls the addition of metal in liquid or powder form to the object, usually by adding one layer at a time. Manufacturers generally used 3D printing for prototyping until the 2000s due to limitations in precision and repeatability. However, technological improvements since then made metal additive manufacturing suitable for commercial manufacturing.
The term “3D printing” originally referred only to printing processes that involved depositing a binder material onto a powder bed with an inkjet printer. However, 3D printing now includes a wider variety of additive manufacturing techniques such as polymer, inkjet and stereo lithography technologies. The term “additive manufacturing” (AM) is more commonly used to refer specifically to metalworking and the production of end-use parts.
3D manufacturing processes began development during the 1980s, when they were known by more specific names such as direct metal laser sintering, selective laser melting and selective laser sintering. At that time, manufacturers associated the process of transforming raw metal into a desired shape only with subtractive processes that removed material. Common techniques of this type include computer numerical control (CNC) milling and electric discharge machining (EDM). Researchers at Carnegie Mellon University and Stanford began development on AM processes in the mid-1990s, beginning with sprayed materials and microcasting. Later improvements included the use of sacrificial and support materials to create objects with new geometries.
Additive processes became commercially viable alternatives to subtractive techniques in metal manufacture during the 2010s, especially for large parts. For example, engine brackets are often grown rather than milling them from stock bars or plates. Traditional techniques such as casting, fabrication, machining and stamping are still more prevalent, but the use of AM is increasing rapidly due to its advantages in creating complex parts. Experts are also speculating that AM can aid the developing world in sustainable development.
The resolution that a 3D printer provides is sufficient for many applications but finishing techniques can further improve the accuracy of AM manufacturing. These processes generally involve printing an oversized object and removing material from it with subtractive processes that have a higher resolution than the printer. The layered approach of AM also lends itself to strain-stepping effects for curved and tilted surfaces based on the surface’s orientation during production. Metal 3D printers require manufacturers to remove the metal component after the substrate has been deposited onto the part. The latest gas metal arc welding (GMAW) techniques also remove aluminum and steel from the substrate surface.