3D Printing: Additive Manufacturing
How 3D printing builds objects layer by layer — the main technologies (FDM, SLA, SLS, metal powder-bed), where they win against machining, and where they still lose.
3D printing (additive manufacturing) builds objects by adding material layer by layer from a digital model, instead of subtracting it from stock (machining) or forming it in a mold. The first commercial processes appeared in the late 1980s; the technology now spans hobbyist toys, dental aligners, aerospace fuel nozzles, and patient-specific implants. Its defining trade-off is geometric freedom versus throughput.
The main processes
FDM (fused deposition modeling): a heated nozzle extrudes thermoplastic filament (PLA, ABS, PETG) layer by layer — cheap, slow, strong enough for prototypes and housings, the technology that made desktop printing common. SLA/DLP (resin): a UV laser or projector cures liquid photopolymer resin layer by layer; resolution is superb (tens of microns) and surfaces are smooth — dental, jewelry, and miniatures. SLS/MJF (powder bed): a laser or IR fuses nylon powder; no support structures are needed because the powder is self-supporting, so this is the workhorse for complex functional parts. Metal powder-bed fusion (SLM/DMLS): the same idea in titanium and stainless steel, used for aerospace brackets and implants (stress and strain matters here: layer interfaces and roughness seed fatigue cracks).
What it is and is not good for
Additive wins on: one-off complexity, internal channels, mass customization (hearing aids, dental aligners), and parts whose geometry would be impossible to machine. It loses on cost per part at volume (injection molding is orders of magnitude faster per unit), on material choice (polymers and some alloys; not commodity steel), and on surface finish without post-processing. The design rule: 3D printing is for geometry that subtractive methods cannot make or that customizes per unit; conventional manufacturing wins on identical parts at scale. Related reading: the industrial revolution for the previous geometry-revolution in manufacturing.
Tags
3d printing additive manufacturing engineering manufacturing