As the name indicates, rapid prototyping (RP) has traditionally been used to provide a physical representation of a product in a relatively short time. RP is performed by either material removal or material addition. In material-removal type RP processes, the part is produce by machining it is out of a block of material; mainly using computer numeric controlled (CNC) machining centers. In material-addition type RP, the prototype is made by adding layers of materials using one of the available RP technologies.