Direct Metal Laser Sintering — invented by EOS GmbH in 1987, commercialized in the 1990s — fully melts pre-alloyed metal powder with a focused laser beam. The “sintering” in the name is a historical artifact. The physics is fusion.
Core Process Parameters
Laser power (P): 200–400W for most materials. Higher power increases melt pool size and build rate; lower power improves feature resolution.
Scan speed (v): 800–1,600 mm/s typical. Higher speed reduces energy per unit length.
Hatch spacing (h): 0.05–0.15 mm. Overlap between adjacent laser tracks determines melt pool connectivity.
Layer thickness (t): 20–100 µm. Thinner layers: better resolution, slower build. 50 µm is the most common production setting.
Energy Density
The combined effect of these parameters is expressed as volumetric energy density:
E = P / (v × h × t) [J/mm³]
Target: 50–100 J/mm³ for most alloys. Below this range: lack-of-fusion porosity. Above: keyhole porosity from excessive melt pool vaporization.
Build Strategy
Scan pattern: Island scanning (5×5 mm or 7×7 mm squares, rotated 67° per layer) distributes thermal stress and prevents systematic directionality in mechanical properties.
Support structures: Required for geometry below 45° from horizontal. Supports conduct heat and prevent warping. Lattice supports preferred over solid for easier removal.
Part orientation: XY orientation (flat on build plate) maximizes accuracy and surface finish. Z orientation (tall, vertical) maximizes build productivity but reduces XY-plane resolution.