These would include machining processes such as milling, turning, and grinding. Machining methods are difficult to use on parts with very small internal cavities or complex geometries. Compressive processes, also conventional, include casting and molding. The new rapid prototyping technologies are additive processes. Photopolymer systems start with a liquid resin, which is then solidified by discriminating exposure to a specific wavelength of light.
Thermoplastic systems begin with a solid material, which is then melted and fuses upon cooling.
The adhesive systems use a binder to connect the primary construction material. Rapid prototyping systems are capable of creating parts with small internal cavities and complex geometries. Also, the integration of rapid prototyping and compressive processes has resulted in the quicker generation of patterns from which molds are made. Rapid prototyping was commercially introduced in 1987 with the presentation of StereoLithography. Conventional Prototyping The machining methods of prototyping should not be underestimated.