Building prototypes and finished parts in a machine from powdered thermoplastics and metals that are cured by heat from a laser. From CAD drawings that have been cross sectioned into thousands of layers, the machine builds up the part by curing one layer at a time. Powder is added for the next layer, and at the end of the job, the excess powder is removed and recycled for the next product. Also called "selective laser sintering" (SLS), it is one of several additive fabrication technologies used in rapid prototyping and rapid manufacturing. See 3D printing for an overview of the major methods.