DMLS uses a high-power fiber laser (typically 200–1000 W) to selectively fuse fine metal powder—usually 20–50 μm particles of titanium, Inconel, stainless steel, aluminum, or cobalt-chrome—into fully dense parts, one ~30 μm layer at a time. Unlike SLS (which only sinters polymer), DMLS achieves near 100% density, with mechanical properties rivaling wrought material after heat treatment.

How the process works:

• A recoater blade spreads a thin powder layer across a heated build plate inside an inert chamber (argon or nitrogen, <0.1% O₂ to prevent oxidation).
• The laser scans the cross-section, melting powder into the layer below. Scan strategies (stripes, chessboard, rotated hatches) control residual stress.
• The plate drops one layer thickness; recoater spreads fresh powder; repeat. A typical part takes 20–80 hours.
• Post-processing is mandatory: stress relief in a furnace, wire-EDM removal from the build plate, support removal, HIP to close microporosity, and CNC finishing of critical features.

Why engineers use it: DMLS lets you build geometries impossible to machine or cast—internal conformal cooling channels, lattice structures, topology-optimized brackets that consolidate 20 parts into 1. GE's LEAP fuel nozzle is the canonical example: 18 brazed pieces became a single DMLS part, 25% lighter and 5× more durable, now flying on every LEAP engine.

Critical design rules:

• Overhang limit: features below ~45° from vertical need support structures—or they'll droop, curl, and fail. Self-supporting angles are the cheapest design choice.
• Minimum wall thickness: ~0.4 mm, but expect warping below 1 mm on large parts.
• Residual stress: the laser heats spots to 2000+ °C then they cool in milliseconds—this builds enormous internal stress. Parts can warp off the plate or crack during build. Heat-treat before removing from the build plate.
• Surface finish: as-built Ra is 6–15 μm (rough). Anywhere you need a seal, fit, or fatigue performance, plan to machine it.

Rule of thumb for cost: DMLS runs roughly $5–$15 per cm³ of part volume in titanium or Inconel, plus machine time (~$50–$150/hour). A part the size of a fist in Ti-6Al-4V typically costs $1,500–$4,000. This only beats machining when you're consolidating multiple parts, eliminating long tool paths, or building geometries no subtractive process can reach. For simple brackets at production volume, casting or machining still wins.