Metal 3D printing (DMLS/SLM): how it works, costs and design rules

A laser melts fine metal powder layer by layer into dense metal parts. It suits complex, lightweight and consolidated parts in aerospace, medical, tooling (conformal cooling) and motorsport.

Typical tolerance

±0.1–0.2 mm as printed; machined faces as for CNC

Quantities

1 to a few hundred

Lead time

7–20 working days

Materials

Stainless 316L, 17-4PH, maraging steel, AlSi10Mg, Ti-6Al-4V, Inconel

How it works

Thin layers of powder are melted by one or more lasers in an inert gas chamber. Parts are built on a base plate with supports, stress relieved, removed by EDM or sawing, and often machined on critical faces.

Benefits

• Shapes impossible to machine or cast: internal channels and lattices.
• Several parts consolidated into one.
• Weight savings through topology optimisation.

Limitations

• High cost per cm³.
• Supports and residual stress need careful design.
• As-printed surfaces are rough; precision features need machining.

What drives the cost

• Build height (layers) and part volume.
• Support removal, heat treatment and machining.
• Material (titanium and nickel alloys cost more).

Design rules

• Keep overhangs above about 45° from horizontal or add supports.
• Add 0.5–1 mm machining stock on precision faces.
• Make internal channels self-supporting (teardrop or diamond shaped).

Preparing your STEP file

• Send two STEP files: the printed shape (with machining stock) and the final machined part.
• Mark which faces are machined after printing on the drawing.

See also the full STEP export checklist and the comparison of all processes.