“Additive fabrication” refers to computer controlled build processes where materials are deposited in layers and aggregated to construct three dimensional objects. Three dimensional design data (often generated as a digital model) is used to drive 3D printers which deposit plastics, clay, powders, or some forms of metal.
Many fabrication methods create objects through the removal of material (milling and cutting). These “subtractive” processes generate waste through material loss. Additive fabrication places specific amounts of material to produce a desired form, significantly reducing the amount of waste generated to produce a physical part. Complexity is achievable using both additive and subtractive methods, but additive fabrication has advantages. Objects with latticed or networked interiors are more easily made using additive fabrication methods for example.
In flat-layer additive fabrication, amorphous material in the form of a liquid, powder, or adhesive film is built-up sequentially in flat layers to form a desired shape. This can be accomplished through a variety of techniques. Five common techniques are as follows: “Selective Surface Curing” applies a laser to set successive layers of liquid resin. “Pattern Lamination” bonds and then cuts successive patterns using layers of adhesive film. “Deposition” involves the placement of successive layers of a fusible material. “Selective Sintering” describes the process of depositing successive layers of a meltable powder and then sintering them using a laser. Sintering is the process of forming a solid mass of material using heat (laser) or pressure without melting it to the point of liquefaction. “Stereolithography” is another 3D printing process where a light-emitting device (laser or DLP) selectively illuminates the transparent bottom of a tank filled with a liquid photo-polymerizing resin. The solidified resin is progressively dragged up by a lifting platform, resulting in a 3D object.
Each approach has advantages and limitations. These include speed of production, cost of the machine, cost of the final build, durability or flexibility of the build (how will the prototyped piece be used and is the material appropriate to that use), aesthetics, and resolution.