3D Printer Filament Extruded from Pellets

Filament is made the way a 3D printer prints, only continuously: dry plastic pellets fall from a hopper onto a turning screw inside a heated barrel, melt as they are carried forward, and are pushed out through a round nozzle. The strand is cooled in air or a water bath, drawn by a puller at a steady speed so it keeps its diameter, and wound on a spool. Commercial 1.75 mm filament is typically held to about ±0.02 mm; a small line should be measured. PETG and many other plastics take up moisture, which makes bubbles and weak prints: makers dry PETG at about 55–70 °C for 5–8 hours, depending on the resin. Melt temperatures follow the resin's datasheet; PETG is usually printed at about 230–260 °C.