SLA (Stereolithography) technology was invented by Chuck Hull in 1984 and has now become one of the popular technologies in the field of 3D printing. The operating principle of SLA technology is based on the principle of polymerization (moving from liquid to solid) of materials under the effect of light emitted from a laser source (usually Ultraviolet). According to the diagram below we can see the laser is controlled by the Scanning mirrors to scan the laser on the surface of the printed material. When the laser beam hits, the top layer of liquid material will solidify, then the printing bed will move downwards with a distance exactly equal to the thickness the layer of material that has just solidified. Next, the Recoater part will pull over to create a new layer of liquid material for the laser to scan, this process is repeated until the object is printed according to the 3D drawing. 

The feature of SLA 3D printing technology is to produce products with high accuracy and surface definition, so it is often used to print 3D models, print tools in a short time, print final products for medical, dental, etc. Another important feature of SLA printing technology is the uniformity of the material (isotropic) after printing. This is a big advantage of SLA technology over some other 3D printing technologies.

Source: Formlabs

SLA printing materials are divided into the following categories: standard, engineering materials, high ductility and elastic materials, high hardness materials, dental materials, jewelry materials, special resin material, v.v.

Source: Formlabs