Intro to Rapid Prototyping

A 3-D CAD model is processed to create a file that can be interpreted by the stereolithography computer. This data is mathematically processed to yield a series of cross sections (layers). Next, computer-controlled mirrors direct an ultraviolet beam across the surface of a vat containing photo-curable liquid polymer. The laser traces the path of the cross section, changing the liquid into a solid, until a new layer is formed. This newly-formed layer is then lowered into the vat by an elevator, while a recoating and leveling system establishes the thickness for the next layer (from .002' to .006' thick depending on the SLA machine used). The part is built layer by layer, one on top of another, each adhering to the last, until a three dimensional part is formed.

PolyJet, or multi-jet modeling, is a 3D printing process where photopolymers are jetted on to a build platform, then parts are built up layer by layer. In this case, those layers can be as small as 16 microns, with 600x600 dpi.

Room Temperature Vulcanization (RTV) molding is the fastest, most accurate, and least expensive way to create 1 - 100 duplicates of a prototype part, including small details on the original part.

The rubber mold is formed from a high level finish existing part or "pattern", A stereolithography (SLA) part is commonly used for the pattern. The SLA part is sometimes oversized to allow for shrink rate of the resin used. The SLA is surrounded by a surface to create the parting line to open the completed mold. A liquid RTV rubber is poured over the master pattern, including parting surface. After the rubber has solidified, the mold is split and the pattern is removed producing a two piece rubber tool.