One idea, two implementations
Selective laser sintering and HP Multi Jet Fusion both build a part inside a bed of polymer powder. Unfused powder supports the part as it grows, so there is no support structure to design around, nothing to remove, and no marks on the supported faces. That single property changes what you are allowed to design.
SLS fuses powder with a laser tracing each cross-section. MJF jets a fusing agent across the whole layer and then applies infrared energy, fusing the layer in one pass rather than one path. In practice MJF is faster per layer and more consistent across a densely packed bed; SLS has the wider material range.
What this buys you
- Geometry that FDM cannot build — internal channels, lattices, organic shapes, unsupported overhangs at any angle.
- Genuine three-dimensional nesting — parts stack in the bed in all three axes, not just across a plate, so quantity economics are much better than they look at quantity one.
- More even strength — still not isotropic, but far less directional than an extruded part.
What it costs you
A grainy matte surface, which is characteristic rather than a defect and can be improved by bead blasting, tumbling or dyeing. Powder must be able to escape from internal volumes, so a sealed cavity becomes a trapped block of powder — designs need escape holes. And the whole bed has a thermal history, so a part built at the edge of a densely packed bed does not behave identically to one built in the middle.
If you are printing with FDM instead
Many parts that seem to need a powder bed can be adapted to FDM: split a part with internal channels into two halves, replace unsupported overhangs with chamfers, and orient the load along the layers. FDM explained and Build orientation show how.