3D printing (additive manufacturing)
also: 3D printing · FDM · SLA · SLS · MJF · rapid prototyping
Building parts layer by layer directly from CAD; excellent for fast prototypes, fixtures and complex low-volume parts, rarely cheapest at volume.
The main processes differ a lot. Material extrusion (FDM/FFF) is cheap and fast but shows layers and is weaker between them. Vat photopolymerization (SLA/DLP) gives smooth, detailed parts, often used for appearance models. Plastic powder bed fusion (SLS and similar) makes strong nylon parts without support structures and can serve low-volume production. Metal powder bed fusion makes complex metal parts at higher cost. ISO/ASTM 52900 defines the terminology.
3D printing compresses design iteration from weeks to days and needs no tooling, which makes it ideal for fit checks, works-like prototypes, assembly jigs and custom parts.
Where it bites: printed parts don't behave like molded ones. Strength, shrinkage, surface finish and tolerances differ, so a design validated in print can still fail in production plastic. Per-part cost stays roughly flat with volume, so molding wins at scale.
Founder takeaway
Use 3D printing to iterate quickly, but validate critical mechanical behavior in the production material and process before committing.
engineer review pending