SLA Prototyping – How it works
The model is built one layer at a time from CAD data that guides an Ultra Violet (UV) laser beam directed by a computer guided mirror onto the surface of the UV sensitive liquid epoxy resin. The UV light precisely solidifies the resin it touches. Every pass of the laser fuses another 0.1mm to the preceding layer by constructing the “skin” and then filling in the “core” material. Each layer is applied by submersion of the build platform into the resin.
The paddle sweeps across the surface of the resin with each step downwards, to break the surface tension of the liquid and control layer thickness. The part gradually develops below the surface of the liquid and is kept off the build platform by a support structure. This is made in the same way, prior to building the first layer of the part.
The finished parts are left to drain and then removed from the tank along with any uncured epoxy resin residue. The parts are separated from the build platform and the support structure is detached.
An alcohol-based chemical (isopropinol alcohol) is used to clean off the uncured resin liquid and the parts are then fully cured under intensive UV light for about a minute. The build strata are just visible in the finished part and can be removed with abrasive blasting, polishing or painting.