computerized device that produces a three-dimensional object by creating it as a series of thin layers. The object is created from a model stored in computer-aided design file; the model is sliced into hundreds or thousands of very thin horizontal layers using computer software, and each layer is sent to the 3D printer to be created successively until the entire object is formed. A number of different processes are used by 3D printers to create objects. Droplets of a melted material may be deposited to form the layers, ultraviolet light may be used to harden layers from a pool of photocurable liquid resin, or a laser or electron beam may be used to sinter (see sintering) or melt particles in a bed of powder to form the layers. A wide variety of materials may be used depending on the process, including thermoplastics, metals, ceramic powders, glass, plaster, and chocolate and other foodstuffs.
Originally developed in the 1980s, 3D printing was first used mainly to produce prototypes of manufactured objects. As the size, speed, and cost of 3D printers has been reduced and they have become easier to use, the printers have become more commonplace, and found wider use. A mainstay now of rapid prototyping, they are also used for custom or small-scale manufacturing and to make architectural and other models. The International Space Station, for example, has used a 3D printer to produce a custom wrench from instructions emailed by NASA. Some stents and alternatives to orthodontic braces are made using 3D printers, and artifical limbs, joints, bones, and bone scaffolding for implantation have been produced. Models created with 3D-printers are used to prepare for complicated surgical procedures. So-called bioprinters are being explored as a means of creating individualized tissues and organs for transplantation. Less expensive 3D printers are available for use by the hobbyist, and 3D-printing services are available to create objects for those who cannot afford a printer or only need to use one occasionally.