Stereolithography is a process where a vat of UV curable photopolymer resin is cured by a laser to build parts one layer at a time. It begins with the generation of the final 3D part as an STL file, which is then sliced into layers at the same thickness that the machine builds – this is typically 0.05 to 0.15mm. These slice files are then transferred to the SLA machine where the parts will be built layer by layer. Components can be converted to STL from other CAD file types, or can be created using a CAD design service.
The laser then scans across the elevator platform, drawing the cross section of the first layer. Once the laser has finished drawing this cross section, the elevator platform lowers by a distance equal to that of one part layer & a recoater blade then sweeps across the vat, re-coating it with fresh resin. The process is then repeated, layer-by-layer, until all the parts have built to their full height.
SLA requires the use of support structures for a number of reasons: Firstly, they are needed to anchor the parts to the elevator platform to prevent them from floating away in the vat of resin. Secondly, they are required to prevent any deformation in the part whilst it is building. Especially with tall parts, they could be susceptible to movement within the vat – the support structures help prevent them from moving about. Once the part has finished building, these support structures must be removed (usually by hand) before the component can be finished & used.
Once the parts are built, the excess resin must be washed off – they are then ready for the finishing process. In order to be ready for end use, the parts require post-curing in a UV oven. Prior to this, any finishing of the parts can be undertaken. The finished parts may have some faceting & layer lines left over from the build process – these can normally be removed quite easily by hand. Once post-cured, there are a number of painted & metal coated finishes that can be applied to SLA parts to provide a multitude of finishes.