Introduction to Rapid Prototyping
In research, development and study, prototypes play an important role. These developed prototypes help to do testing prior to production and help to pinpoint the possible problems that are occurring due to the design faults. Earlier generating a Rapid Prototype model was extremely costly process and also time taking. But with the aid of Computer Numerically Controlled (CNC) Machining, the speed at which a prototype is developed has increased. With Rapid Prototyping, this time period has even decreased from few days to a few hours.

Rapid Prototyping is an additive manufacturing process that generates a model of an object directly from a CAD model by building it in layers. For this computerized equipment are used that builds a three-dimensional model of a casting from a CAD drawing.

There are different forms of  plastic mould  available depending upon the needs. One can differentiate between them by the methods these systems employ to make the layers. Following are few of the main types of Rapid Prototyping:

Stereolithography (SLA)
Stereolithography uses UV ray to solidify liquid acrylic polymer layer by layer on a moving platform and after many layers, the plastic mould in the preferred form is formed. This process is carried on in a VAT, a device that is filling up with photocurable liquid acrylate polymer. Stereolithography is one of the most used forms of rapid prototyping because of accuracy (Tolerances= 0.0125mm), less time taken (depends upon the size and complication of the part) and where parts details are fine and their geometry is to difficult to machined.

Fused Deposition Modeling (FDM)
Fused deposition modeling also referred as FDM, is a rapid Rapid Prototype technology commonly used to convert CAD drawings into physical parts. FDM is a trademark of Stratasys and was developed by S. Scott Crump.

FDM works on an “additive” principle which extrudes material in layers. Plastic or wax is melted and liquefied in the extrusion head and extruded through a nozzle. The nozzle is made to move over a trail identified by the CAD design to produce part. This way single layer is extruded and then it is dropped to extrude the next layer on top of the first until the entire prototype is built, with one layer at a time.

Selective Laser Sintering (SLS)
Selective Laser Sintering uses the principle of sintering. Sintering is a heating process that prevents melting and a coherent mass is produce. In SLS, metallic or non-metallic powders are sintered using a CAD program guided laser that selectively fuses the powdered material.

There are few more types of plastic mold  available, like; Laminated Object Manufacturing, 3D Printing, Solid Base Curing, Optical Fabrication and Photochemical Machining.

Rapid prototyping has provided designers with several benefits. Designers can look their parts and in case any error occurs they can easily fix it. Apart from industrial use they have formed part of manufacture. This development process provides blank patters for use in casting. RP has also proliferated biomedical science.