Definition
Filament
noun, 3D printing
Filament is the plastic wire an FDM 3D printer melts and lays down, layer by layer, to build a part. It comes on a spool, usually 1.75 millimeters thick, and feeds into a heated nozzle called a hotend.
Diameter
1.75mm
Spool weight
1kg (typical)
Form
Solidthermoplastic
Melt method
Hot end180 to 260 °C
Common types
6+PLA, PETG, ABS...
Feed
Pushedby extruder
What it is made of
Most filament is thermoplastic, meaning it melts when heated and sets when it cools. That melt-and-set cycle is what lets the printer stack layers that fuse into a solid object.
The common types are PLA, PETG, ABS, ASA, TPU, and nylon. Each mixes ease, strength, heat resistance, and flexibility differently, so the right one depends on what the part has to survive.
How a printer uses it
A motor pushes the filament from the spool into the hotend. The hotend melts it, and the printer moves the hotend along a path, depositing a thin bead. One layer at a time, the part grows from the bed up.
For a walkthrough of the easiest filament to start with, read the PLA guide.
Related guides
Sources & methodology
3 citations · reviewed 2026-07-10- 01ISO/ASTM 52900:2021 additive-manufacturing terminologyaccessed 2026-06-29Tier 1
- 02Bambu Lab PLA Usage Guide (wiki): filament diameter and material behavioraccessed 2026-06-29Tier 1
- 03All3DP 3D Printing Terminology glossaryaccessed 2026-06-29Tier 2