The platform in the tank of photopolymer at the beginning of a print run.

The Stereolithography Process

The basic printing process goes like this:

  • You create a 3-D model of your object in a CAD program
  • A piece of software chops your CAD model up into thin layers -- typically five to 10 layers/millimeter
  • The 3-D printer's laser "paints" one of the layers, exposing the liquid plastic in the tank and hardening it
  • The platform drops down into the tank a fraction of a millimeter and the laser paints the next layer
  • This process repeats, layer by layer, until your model is complete

This is not a particularly quick process. Depending on the size and number of objects being created, the laser might take a minute or two for each layer. A typical run might take six to 12 hours. Runs over several days are possible for large objects (maximum size for the machine shown above is an object 10 inches (25 cm) in three dimensions).

You start by creating a 3-D design for your object in a CAD program. This design is tweaked before building with supports that raise it up off the tray slightly and with any internal bracing that is required during building. The SLA then renders the object automatically (and unattended). When the process is complete, the SLA raises the platform and you end up with your 3-D object. If the object is small, you can produce several of them at the same time if you like. They all sit next to each other on the tray.

The following photo shows a tray after building is complete, with several identical objects that were produced simultaneously:

The platform at the end of a print run, shown here with several identical objects.

Once the run is complete, you rinse the objects with a solvent and then "bake" them in an ultraviolet oven that thoroughly cures the plastic.

The ultraviolet "oven" used to cure completed objects.