When a 3D CAD model of a part has been uploaded by a customer, it is moved into a scheduling and build queue. All of the part files are downloaded and the geometry is analyzed for any potential manufacturability issues. If any issues do arise, a dialog between a Proto Labs representative and the customer will take place to resolve the problem before the actual build begins.
As the stereolithography build prep begins, parts are digitally positioned onto the build platform and the necessary support structures are strategically placed onto the part. Automated supports are initially placed followed by supplemental supports done manually to provide a comprehensive final support system. Because part features are imaged on the surface of liquid, if the parts are not supported in the SL process, they would float away or collapse during the build.
Build prep technicians then go through a layer-by-layer review of the build to ensure that all of the features are adequately supported for a successful build (With an average build height of 1 to 2 inches, for example, there would be approximately 500 to 1,000 layers.) Once the review is complete, the technicians will digitally create the required amount of copies required for a particular order before it is ultimately sent to the SL machine.
The machine begins drawing the layers of the support structures, followed by the part itself, with an ultraviolet laser aimed onto the surface of a liquid thermoset resin. After a layer is imaged on the resin surface, the build platform shifts down and a recoating bar moves across the platform to apply the next layer of resin. The process is repeated layer by layer until the build is complete.
The tray containing the newly built parts is taken out of machine and into a lab where solvents are used to remove any additional resins. When the parts are completely clean, the support structures are manually removed. From there, parts undergo a UV-curing cycle to fully solidify the outer surface of the part. The final step in the stereolithography process is the application of any customer-specified finishes — unfinished, natural finish (sanding of the supported surfaces to remove any evidence of support), standard finish (400 grit matte finish with a grit blaster in addition to sanding supported surfaces) and custom finishing (ranging from colored paint to optically clear lenses to decals and lettering.)
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