What Is a DMLS (Direct Metal Laser Sintering)?

DMLS (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. It is a laser powder bed fusion process, closely related to SLM, used for complex components in stainless steel, aluminum, titanium, nickel alloys and cobalt-chrome.

In short: DMLS prints metal parts directly from CAD, including complex shapes that would be difficult or expensive to machine.

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

	DMLS	SLS
Feedstock	Metal powder	Polymer powder (mostly nylon)
ISO/ASTM category	Powder bed fusion	Powder bed fusion
Support structures	Needed under overhangs and to anchor the part to the build plate	Not needed; loose powder supports the part
Typical post-processing	Stress relief, removal from the plate, support removal, surface finishing or machining	Powder removal, optional sanding, painting or dyeing
Layer thickness at NICE Rapid	20–60 µm (0.0008–0.0024 in)	100–180 µm (0.004–0.007 in)
Tolerance at NICE Rapid	±0.1 mm (±0.004 in)	±0.2 mm (±0.008 in)
Lead time at NICE Rapid	5–10 days	2–3 days

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.

NICE Rapid prints metal parts by DMLS / SLM in-house in 316L stainless steel, AlSi10Mg aluminum, Ti-6Al-4V titanium, Inconel 625/718 and cobalt-chrome.

Frequently Asked Questions

What is DMLS?

DMLS is a metal 3D printing process in which a high-power laser fuses fine metal powder, layer by layer, into a dense metal part. It belongs to the powder bed fusion family and is used for complex metal components that would be difficult or expensive to machine.

What does DMLS stand for?

DMLS stands for direct metal laser sintering. Despite the word "sintering," it is the same laser powder bed fusion principle as selective laser melting (SLM): a laser fuses metal powder one thin layer at a time.

What is the difference between DMLS and SLM?

In practice, there is very little difference. DMLS, SLM and DMLM all use a laser to fuse metal powder in a powder bed, and the names are simply different trade names for the same process.

Related Services at NICE Rapid

• 3D Printing — in-house DMLS / SLM in stainless steel, aluminum, titanium, Inconel and cobalt-chrome, with ±0.1 mm tolerance and 5–10 day lead times.
• CNC Machining — 3-, 4- and 5-axis milling and turning to ±0.01 mm, for metal parts that are better machined from solid.
• Request a Quote — upload a STEP file and our engineers will recommend printing or machining for your part.

Sources

1. NIST, Additive Manufacturing: Powder Bed Fusion — melting and fusing layers of powdered material (e.g., metal) with a high-power laser or electron beam; "repeated hundreds or thousands of times, building the metal piece layer by layer"; excess powder removed at the end; NIST's laser powder bed fusion system builds in stainless steel, aluminum, titanium alloy, nickel alloy and cobalt-chrome powders — nist.gov
2. Çelik et al., "Contact-Free Support Structures for the Direct Metal Laser Melting Process," Materials — DMLM, DMLS and SLM "have the same working principle… denominated distinctly by different tradenames"; STL slicing and layer-by-layer process on a build plate; supports needed beneath overhangs and their removal adds time and cost; post-process surface treatments including CNC machining — pmc.ncbi.nlm.nih.gov
3. Paraschiv et al., "Assessment of Residual Stresses in Laser Powder Bed Fusion Manufactured IN 625," Materials — residual stresses from high temperature gradients and rapid cooling; stress-relief heat treatment before detaching parts from the baseplate is the primary approach — pmc.ncbi.nlm.nih.gov
4. Koltsaki et al., "A Comprehensive Overview of Additive Manufacturing Processes Through a Time-Based Classification Model," 3D Printing and Additive Manufacturing — ISO/ASTM 52900 powder bed fusion terminology includes SLM and DMLS — pmc.ncbi.nlm.nih.gov