Powder bed fusion is the family that spreads a thin layer of powder and fuses selected areas of it with a laser or electron beam, then lowers the platform and repeats. It covers most industrial metal printing and the sintered nylon that produces the best functional polymer parts, and it is defined as much by its powder handling as by its beam.
How the cycle works
A recoater spreads a layer of powder tens of micrometres thick across the build area. The beam scans the cross section, fusing the powder to itself and to the layer beneath. The platform drops by one layer thickness and the recoater passes again. Unfused powder remains in place, supporting polymer parts entirely and metal parts partially, since metal still needs structural supports for heat and stress.
Polymer against metal
In polymer powder bed the whole chamber is held just below melting point so the laser only has to add a little energy, which is why parts need no supports and can be nested densely in three dimensions. In metal powder bed the process runs in an inert atmosphere, parts are welded to a build plate, supports carry heat and resist distortion, and residual stress is a first order concern.
Powder is a controlled material
Particle size distribution, sphericity, flowability and oxygen content all affect the result, and powder is partially reused between builds with refreshing and sieving. In regulated work powder lots are traced. Fine metal powders are also a genuine health and explosion hazard, so handling, extraction and inert conditions are part of what a facility must have rather than optional practice.
What it gives and what it costs
The best combination of resolution, density and properties in additive manufacturing, and in polymers the only common process producing genuinely functional isotropic parts with no supports. Against that: machine and powder cost, build time driven by height and area, and in metals a post processing chain that usually costs more than the build.
Questions people ask about powder bed 3d printing
What is powder bed fusion?
An additive process family that spreads thin layers of powder and fuses selected regions with a laser or electron beam, building the part inside the powder bed.
Do powder bed parts need supports?
Polymer parts do not, because the surrounding powder supports them. Metal parts do, because supports anchor the part to the plate and conduct heat away.
Is powder reused?
Yes, with sieving and refreshing with virgin powder. Reuse ratios are controlled, and in regulated work powder lots are traced through to the part.
Is metal powder dangerous?
Fine metal powders present real inhalation and explosion hazards, which is why handling, extraction and inert atmospheres are part of a facility's requirements rather than optional.