Rapid prototyping was introduced in 1987. This technology is an additive process. An additive process builds an object by joining particles or layers of raw material. Other conventional processes are subtractive and compressive. Materials used for the additive process are photopolymers, thermoplastics, metal powders, and ceramic powders.

Stereolithography, which was one of the first rapid prototyping technologies, is a method that uses photopolymer in a vat. A laser generates an ultraviolet beam that solidifies focused surface areas of the photopolymer. The process begins with the vat filled with the photopolymer liquid. The operator loads a three dimensional CAD solid model file into the system. The control unit slices the model and supports into a series of cross sections from 0.004 to 0.020 inches thick. The computer-controlled optical scanning system directs and focuses the laser beam so that it solidifies a two -dimensional cross section on the surface of the photopolymer. The product turns to cover the solid polymer with another layer of the liquid. This process continues, building the part from the bottom up, until the system completes the product.

There are many other rapid prototyping technologies such as selective laser sintering (SLS), fused deposition modeling (FDM), fused peposition modeling (FDM), etc.