3D printing · process family

SLS / MJF / DMLS

Powder bed fusion · SLS · MJF · SLM · DMLS · EBM

Fuse a bed of powder selectively, then spread the next layer on top

A thin layer of fine powder is spread across the build area and fused selectively — by a laser, by infrared over a printed fusing agent, or by an electron beam. Because the surrounding loose powder supports the part, no support structures are needed, so complex and nested geometries print freely. It gives the strongest, most isotropic polymer parts of the common processes — the go-to for end-use plastic and for metal.

spread · scan · fuse
SLS / MJF / DMLS — fuse a bed of powder selectively, then spread the next layer on top.
0.06–0.12 mm layers
Resolution
Moderate (whole layer on MJF)
Speed
$$$
Cost
Best (of the polymer processes)
Isotropy

How it works

  1. 1
    A recoater blade or roller spreads a thin layer of powder across the bed.
  2. 2
    The layer's cross-section is fused — laser (SLS/SLM), fusing agent + IR lamp (MJF), or electron beam (EBM).
  3. 3
    The build platform drops one layer and fresh powder is spread on top.
  4. 4
    Repeat; the un-fused powder bed supports every overhang, so no supports are printed.
  5. 5
    Cool the cake, then de-powder and (for metal) cut parts off the build plate.

The machines

The variants of this family, from the hobby basics to the industrial state of the art.

SLS (polymer)

Industrial

A CO₂ laser sinters nylon-family powders. Strong, near-isotropic functional plastic parts; the workhorse of the polymer side.

Multi Jet Fusion (MJF)

Industrial

HP's process jets a fusing agent onto the powder, then fuses a whole layer under an IR lamp — faster and more uniform than point-by-point lasers.

SLM / DMLS (metal)

Industrial (metal)

A high-power laser fully melts metal powder (titanium, aluminium, steel, Inconel) — the dominant metal AM route. Needs supports and heat management.

EBM (metal)

Industrial (metal)

An electron beam melts metal in a vacuum at high temperature — fast, low residual stress, but coarser than laser. Used for titanium implants and aerospace.

Strengths & limits

Strengths
  • No supports — the powder bed holds the part
  • The strongest and most isotropic of the common processes
  • Nests many parts densely in one build
  • Complex internal channels and lattices print freely
Limits
  • Grainy, matte surface finish
  • Higher machine and material cost; powder handling and safety
  • Polymer choice is narrow — PA12 dominates
  • Un-fused powder ages; refresh ratios add cost

Typical parts & materials

Feedstock: Fine polymer or metal powder · Thermoplastics (mostly nylons) and metals.

Typical parts: End-use functional parts, complex ducting and manifolds, low-volume production, metal aerospace and medical parts

Commonly run in — open one for its cited properties:

PA12 (nylon powder)PA6TPUPP

What's new

MJF and cheaper benchtop SLS pulled polymer powder-bed cost down and speed up, and the metal side (SLM/DMLS) is now mainstream for aerospace and medical. New polymer powders — PP, TPU, PA11 (bio-based) and flame-retardant grades — are widening a historically narrow material set.

Part of the 3D printing guide. Compare the other process families, see the design rules, or browse the cited materials database.