DefinitionDMLS (direct metal laser sintering) is a metal 3D printing process in which a high-power laser selectively fuses fine metal powder, layer by layer, into a dense metal part.
Explained
How Does DMLS Work?
The CAD model is exported as an STL file and sliced into thin layers, and a laser path is generated for each one. The machine spreads a layer of metal powder on a build plate, and the laser melts the powder along that layer's path. The melted tracks solidify and fuse to the layer below. NIST describes the cycle as "repeated hundreds or thousands of times, building the metal piece layer by layer." At the end, the excess powder is removed.
DMLS vs SLM. DMLS, SLM (selective laser melting) and DMLM (direct metal laser melting) share the same working principle: a laser is the heat source that fuses metal powder. They are different trade names for one process, which ISO/ASTM 52900 groups under powder bed fusion. NICE Rapid lists its metal process as DMLS / SLM for this reason.
Metal powder bed fusion brings two challenges that polymer SLS does not:
- Support structures. Overhanging surfaces need supports beneath them. The supports are removed after the build, which adds time and cost.
- Residual stress. High temperature gradients and rapid cooling leave stress in the part, which can distort it. The most widely used fix is a stress-relief heat treatment done before the part is cut from the build plate.
DMLS vs SLS
Both DMLS and SLS belong to powder bed fusion, but DMLS uses metal powder while SLS uses polymer powder (mostly nylon). DMLS needs support structures under overhangs and to anchor the part to the build plate, whereas SLS does not need supports because loose powder supports the part. Typical DMLS post-processing includes stress relief, removal from the plate, support removal, and surface finishing or machining; SLS post-processing is mainly powder removal with optional sanding, painting or dyeing.
Designing a Part for DMLS
- Minimize overhangs. Every downward-facing surface that needs support adds removal work and leaves marks where the supports meet the part.
- Plan for finishing on critical faces. As-printed powder bed fusion surfaces are relatively rough. Treatments such as CNC machining are applied afterward where a surface is critical, for example for fatigue life. Leave stock on those faces and consider machinability when you choose the alloy.
- Budget for deburring. Plan for finishing where supports are removed.
- Ask whether printing is the right route. For simple prismatic parts, machining from solid is often faster and more precise: at NICE Rapid, CNC holds ±0.01 mm, compared with ±0.1 mm for DMLS. DMLS pays off when the geometry would be difficult or expensive to machine.
Key takeaways
- DMLS uses a high-power laser to selectively fuse fine metal powder into dense metal parts, layer by layer.
- DMLS, SLM and DMLM are trade names for the same laser powder bed fusion process.
- Support structures are required beneath overhangs and to anchor the part to the build plate.
- Residual stress from high temperature gradients is usually relieved by heat treatment before the part is cut from the build plate.
- NICE Rapid offers DMLS layer thicknesses of 20–60 µm, tolerances of ±0.1 mm and lead times of 5–10 days.
- DMLS is most cost-effective for complex geometries that would be difficult or expensive to machine from solid.
Example
Related terms
References
- Additive Manufacturing: Powder Bed Fusion — NIST
- Contact-Free Support Structures for the Direct Metal Laser Melting Process — Materials (Çelik et al.)
- Assessment of Residual Stresses in Laser Powder Bed Fusion Manufactured IN 625 — Materials (Paraschiv et al.)
- A Comprehensive Overview of Additive Manufacturing Processes Through a Time-Based Classification Model — 3D Printing and Additive Manufacturing (Koltsaki et al.)