RP Primer

What is Stereolithography

Stereolithography is a process that provides fast and dimensionally accurate prototype parts.  A 3D CAD file is saved in stereolithography format (.stl), then transferred directly to an SLA machine where it is built into a 3D solid obect.  These parts can be used in a variety of ways to prove your design, get your product to market faster, and ultimately reduce direct development costs. 


The SLA Process

A 3-D CAD model is processed to create a file that can be interpreted by the stereolithography 'slice' computer. This data is then mathematically processed to yield a series of cross sections (layers). Next, computer-controlled mirrors direct an ultraviolet beam across the surface of a vat of 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). Successive cross sections are built layer by layer, one on top of another, each adhering to the last, until a three dimensional part is formed. The build supports are removed, the part is hand finished by craftsmen, and you can now see, touch, and hold the part you designed.


Silicone Rubber Mold Process (RTV)

While Protogenic's Stereolithography (SLA) prototypes can be finished as functional models, they may also be used as masters to cast additional parts. For this process, an SLA master prototype is first generated. The SLA part is made oversize to compensate for shrinkage that occurs when we make the mold and when we cast the urethane.

After customer approval, the master SLA part is hand-finished to a high level, on all exterior surfaces. Texturing, if required, is also done at this time. Next, a skilled craftsman uses the SLA master to produce an RTV (silicone rubber) mold. Once the mold is ready, polyurethane castings are produced.  For additional information about the molding process at Protogenic, please click here.


Polyurethane Part Castings

Applications

    With the RTV molding and casting process, low volumes of prototype parts (25-35 parts per tool, depending on geometry) can be produced quickly, without hard tooling. These parts may serve a variety of purposes, such as: sales and marketing demos, conceptual models, durable representative and functional models, pre-production parts for trade shows, rapid and inexpensive test assemblies, etc.

Available Casting Materials

  • Soft flexible (25 Shore A) materials to hard durable urethanes (85 Shore D) are available. These prototype urethane materials are used to approximate thermoplastic engineering resins, simulating the form, fit, and function of an injection molded component.  Click here to see the Material Specification Sheets for more information.
  • Cast-in custom coloring and texturing is our specialty, as is 'soft touch' grip, component, and gasket overmolding.
  • Materials with UL ratings are available.

See FAQ's for additional information.