Heat is generated using a focused heat source, normally a laser, sufficient to melt a thin layer of powder applied to the surface of a substrate. Material is added layer by layer by lowering the build by a small amount and spreading a thin layer of powder over the surface. To create the desired geometry, the heat source is traversed over the powder bed, locally melting small regions to form successive layers. The layers eventually build up to form the solid structure.

Material addition in SLM is very stable. Unlike powder feed systems, unmelted material is not lost and can generally be reused. Furthermore, because the layer height is defined by the amount the build chamber is lowered, the layers can be very small, resulting in very fine feature resolution.