Fused filament fabrication (FFF) was developed for the 3D printing of pure thermoplastic polymers. These materials can be shaped when heated and retain their new geometry after cooling.

The polymers are supplied as filament (plastic wire) wound onto spools. This wire is moved towards the heated nozzle by means of an extruder and serves as a piston when still cool and as a material reservoir when molten. Underneath the nozzle, the plastic is deposited on the print bed either during the first layer or subsequently on already printed layers. Once a layer has been completed, the nozzle moves away from the substrate by one layer thickness and a new layer is printed.