Most monofilaments are extruded downwards into a quench bath. This means that the head assembly must contain an elbow to turn the plastic stream 90°. The die is circular in shape, with holes equidistant from the centre. This ensures equal flow through each hole, hence equal filament size.
The material coming out from the die plate is cooled in the quenching bath. Its purpose is to cool the filaments quickly to get a tougher molecular structure of smaller crystallites. The quenching bath temperature is maintained below the crystalline melting point of the material. Cooling medium is usually water with temperature at 40 to 90°C.
Before entering into the drawing oven the filaments must be dried. For this reason, in monofilament lines a drying section is incorporated following the quench bath
At the orientation stage the semi‑plastic filaments are placed under high tension.
Orientation stretches them, the molecules straighten out and line up parallel to the filaments axes, thereby giving them great strength.
Oriented tensile strengths of filaments are sometimes more than ten times the strength of unoriented polymer.
The temperature of plastic during orientation is critical, hence several methods have been devised to maintain the temperature.