Editorial Feature

Rapid Prototyping - Photolithography and Stereolithography

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Time-to-market is turning out to be a highly critical factor for the success of a product, apart from its cost and quality. The time required to create prototypes is a key contributor to product development cycles. Moreover, in markets where customers demand individually customized components, significant time and cost are required to make tools or molds.

Rapid Prototyping (RP), also called Solid Freeform Fabrication (SFF), helps overcome these issues. On the whole, the techniques develop complicated shapes through additive processes, creating components without the application of tools.

Photolithography

The application of laser light or UV for selective curing of resin is the foundation of the Stereolithography Apparatus (SLA), a commercial photolithography RP system. The SLA instrument makes plastic models by photopolymerization of a liquid monomer. The 3D computer-based component design is separated into layers of thickness 0.25 mm.

The laser is subsequently scanned onto the monomer’s surface, defining the cross-section of the component. As soon as the resin is cured, the platform drops 0.25 mm into a vat full of monomer. The liquid monomer flows over the layer and the second layer is scanned. The process is repeated until the part is completed.

Stereolithography Apparatus

Ceramics can be made using photolithography by adding the photocured resin as a binder. The ceramic green shape usually contains 45%–60% polymerized binder (typically UV curable acrylamide monomer) and 40%–55% ceramic powder.

Then, the binder is burnt out and the body is fired to yield a dense ceramic object. A number of ceramic materials, such as Si3N4, Al2O3, and SiO2, have been used to create shell molds or cores for investment casting. Hydroxyapatite has been processed to manufacture bioceramics.

The Al2O3 parts were produced with good surface finish and fine detail. Moreover, there was no distortion, cracking, or delamination witnessed while processing. The drawbacks of the process are warping of components, the need for support structures growing in the resin to make the products, and care required while handling resin since certain resins are poisonous.

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