The making of parts and products using a computer-driven, additive process, one layer at a time. 3D printing builds plastic and metal parts directly from CAD drawings that have been cross sectioned into thousands of layers. It provides a faster and less costly alternative to machining (cutting, turning, grinding and drilling solid materials). Used for making both prototypes as well as final products, 3D printing evolved from the "rapid prototyping" industry, pioneered by Chuck Hull of 3D Systems in the mid-1980s. Concept, Prototype and Final Product Capable of making a part from scratch in just hours, 3D printing is used to create models to determine if a design meets the customer's concept and expectations. It is also used to create prototypes of parts to test their form, fit and function with other parts in an assembly. Using 3D printing technologies such as laser sintering and electron beam melting, "rapid prototyping" evolved into "rapid manufacturing," in which short runs of actual finished parts are made. Such techniques are also used to create products customized for each person, such as hearing aids, dental crowns and medical implants. 3D printing is also used to make tooling, such as molds and dies, as well as patterns for castings. Either the actual mold or the model to make the mold can be produced more quickly and less costly than with conventional methods. Additive Fabrication and 3D Printers Although various techniques are used, all 3D printers use methods of "additive fabrication," methods, building the part one layer at a time, with layers ranging from a millimeter to less than 1/1,000th of an inch. The building material can be a liquid, powder or sheet material that is cured by heat, UV light, a chemical reaction or other method. The term "3D printing" has evolved to include both rapid prototyping and rapid manufacturing. Initially, 3D printers referred only to the relatively small, inexpensive office-based machines that jet a wax, photopolymer or binder. Increasingly, the term refers to any machine that uses a method of additive fabrication either in the office or shop floor.