SLA (stereolithography) is the first of the additive manufacturing processes collectively known as “3D printing”. A special type of liquid plastic is used that reacts with ultraviolet (UV) light to form a solid. An object is created by slowly curing one layer at a time using a programmable UV light source.
SLS (stereo laser sintering) is also a method for making rapid plastic prototypes, but in this case the raw material is a fine powder. A programmed laser is used to fuse the powder into a solid one layer at a time to create the finished product. Objects are created on a build platform, which is carefully controlled by a computer to move down the thickness of one layer with each successive addition of powder.