When a 3D CAD model of a part has been uploaded and subsequently approved by a customer, their confirmed order 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 build prep begins, parts are digitally positioned onto the build platform. One of the big differences between selective laser sintering and stereolithography is that SLS does not require parts to be supported during the build process. Because SLS is a powder-based process, the bed of powder itself serves as the support, essentially allowing the parts to be stacked vertically (or in any direction) as they are being built. As such, a support system is not designed into the part before the build begins.
Build prep technicians then go through a layer-by-layer review to ensure 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 part copies needed for a particular order before it is ultimately sent to the SLS machine.
Using a CO2 laser, the SLS machine begins sintering each layer of part geometry into a heated bed of nylon-based powder. After each layer is fused, a powder deposition system (or roller) moves across the bed to distribute the next layer of powder. The process is repeated layer by layer until the build is complete.
When the build finishes, the entire module is moved into a breakout station. Once the module has adequately cooled, the entire powder bed is raised up and the parts are broken out of the bed. An initial brushing is manually administered to remove a majority of loose powder. Parts then travel to a cabinet where they are bead blasted to remove any of the remaining residual powder before ultimately reaching the finishing department. We will drill out holes as needed, though most holes are designed undersized and do require drilling in SLS. Remaining secondary options (like a primer that can be applied) are much more limited in SLS versus SL.
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