Plastic is melted in an extruder, then passed through a melt pump which meters the flow and pressure of the molten polymer.
The melt pump forces the plastic through the spinneret, which is a die block and consists of many small holes for forming the filaments.
As the plastic exits the spinneret, it is typically quenched in water, while very small diameter fibers may be quenched in air.
The fiber is then drawn to several times the original fiber length in order to increase molecular orientation and tensile strength.
Filament is generally wound onto a spool as a continuous filament, then stored for further processing. Typical plastics used for filament are PE, PP, nylon and polyester.