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Stereolithography is a manufacturing process that uses a UV laser to create
successive cross-sections of a three-dimensional object within a vat of
liquid photopolymer. The cross-sections build layers typically of 0.004
inches or 0.006 inches. A platform is placed on top of the vat filled with
the polymer (an epoxy resin). Just before the build begins, the platform
is moved to a point just below the surface of the resin. As the UV laser
(a Helium-Cadmium laser) traces the layer in the polymer, the resin begins
to cure; thus, solidifying the part to be manufactured.
Before the part begins to build, supports are created between the platform
and the part, to ensure easier removal of the built part. After the supports
are created, the process to build the part begins. Once the cross-section
has been traced with the laser, a Zephyr blade wipes across the platform,
removing the uncured polymer. After a layer has been completed, the platform
drops down again
and the same procedure takes place. The object is manufactured layer by
layer, curing the part on each level. When the build is complete, the
platform raises above the vat, draining the excess resin away from the
part.
The platform is then removed and the part is further processed. The fresh part is bathed in another polymer to remove the excess resin. Now that the part has been sufficiently washed with the TPM solution, it is then sprayed thoroughly with alcohol. This enables the part to be handled directly by human skin (it removes the stickiness or tackiness on the outer edges of the part). The face of the part that was attached to the platform is sanded to remove the support structures. The part is then placed in a UV oven to finish curing the polymer.
When the curing process has finished, the part can be furthered polished and processed, if so desired. The part is usually shipped directly to the company whose design the part was manufactured from, or taken one step further: molding and/or casting. The parts that are built using the stereolithography machine are durable, but fragile. These parts must be handled with extreme care. The dimensions of these parts are very accurate, only varying at times by 0.002 to 0.005 inches. The SLA machine is also highly accurate with building parts containing complex geometries and intricate details.
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