Electron Beam Melting is a powder-bed fusion process that uses a focused beam of high-energy electrons—accelerated to roughly 60 kV—to melt metal powder layer by layer inside a vacuum chamber. It sits next to DMLS in the additive family tree, but the differences in heat source, environment, and thermal regime make it the process of choice for a specific slice of high-value parts: titanium hip implants, Inconel turbine blades, and copper rocket-engine components.

Why electrons instead of a laser? Electrons transfer energy by direct collision with the powder, so coupling efficiency is near 90%—lasers typically achieve 30–40% on reflective metals like copper or aluminum. The beam is steered magnetically (no mirrors, no inertia), letting EBM scan at speeds up to 8,000 m/s and even split into multiple simultaneous melt pools.

The vacuum is non-negotiable. Electron beams scatter off air molecules, so the build chamber operates at roughly 10⁻⁴ to 10⁻⁵ mbar. This is a feature, not a cost: reactive metals like titanium and tantalum absorb oxygen and nitrogen at high temperatures, embrittling the part. Vacuum eliminates this contamination entirely—EBM-built Ti-6Al-4V routinely meets ASTM F2924 medical-implant chemistry without an inert gas purge.

Hot process, low residual stress. EBM preheats the powder bed to 700–1000 °C and keeps it there throughout the build. The whole part stays near a stress-relief temperature, so distortion and residual stresses are dramatically lower than in laser systems. Many parts skip the post-build heat treatment that DMLS components require.

Concrete example: Arcam (now GE Additive) EBM machines produce roughly 100,000 titanium acetabular cups per year for hip replacements. The trabecular lattice on the cup's outer surface—designed to encourage bone ingrowth—is essentially impossible to machine but prints natively in EBM. The vacuum chemistry plus hot build means the cups go straight from machine to HIP to implant qualification with no atmosphere-related rejects.

Rule of thumb for EBM vs. DMLS selection:

• Reactive metal (Ti, Ta, Nb)? → EBM
• Reflective metal (Cu, Al)? → EBM (beam couples better)
• Need sub-50 μm features or smooth as-built surface? → DMLS (EBM minimum feature ≈ 100 μm, Ra ≈ 25–35 μm)
• Thin walls under 0.4 mm? → DMLS (EBM's hot powder cake sticks)
• Large, thick aerospace bracket where residual stress matters? → EBM

The trade-off: EBM parts emerge embedded in a semi-sintered powder cake that must be blasted off with the same alloy's powder ("PRS" — powder recovery system). Surface finish is rougher, fine features are harder, and machines cost roughly twice as much as comparable laser systems.