Three-dimensional printing, commonly called 3D printing, is a form of additive manufacturing in which physical objects are built layer by layer from digital files. The term "additive manufacturing" is the professional name for the same process and stands in direct contrast to subtractive manufacturing, where material is cut away from a larger block, as in CNC machining or milling. Because additive methods only deposit material where it is needed, they tend to produce far less waste than subtractive approaches and can create geometries that would be difficult or impossible to carve.
Several distinct technologies fall under the 3D printing umbrella, each suited to different materials and use cases. Fused Deposition Modeling, also known as Fused Filament Fabrication or FDM/FFF, extrudes melted thermoplastic layer by layer and is the most common consumer method. Stereolithography (SLA) cures liquid resin with a UV laser, while Masked Stereolithography (MSLA) uses an LCD screen to mask a UV light source, and Digital Light Processing (DLP) projects a UV image to cure entire layers at once. Selective Laser Sintering (SLS) fuses powdered material, often nylon, with a laser, and HP's Multi Jet Fusion (MJF) combines infrared heating with a binding agent. Binder jetting sprays an inkjet-style binder onto powder and is common for metals and sand molds, while Direct Metal Laser Sintering (DMLS) is essentially a metal variant of SLS.