Polymer Extrusion Screw

A precision-engineered rotating screw that serves as the core processing element in plastic extrusion machinery. It plasticizes solid polymer pellets through mechanical shear and thermal energy, then conveys the molten material under pressure through the extrusion die. This component directly determines production throughput, melt homogeneity, and energy efficiency in continuous polymer processing lines. As a critical wear part in B2B manufacturing, it represents a recurring consumable in the plastics processing supply chain. The screw's geometry, including diameter, length-to-diameter ratio, channel depth, and compression ratio, is tailored to the specific polymer and application. Typical diameter ranges from 20 to 200 mm, with L/D ratios from 20 to 35. Channel depth varies from 5 to 20 mm, and compression ratios from 2.0 to 3.5. Surface hardness is specified at 58–62 HRC for wear resistance, achieved through nitriding or other treatments. Maximum rotational speed is 120–300 rpm, and operating temperature must match the polymer melting range, typically 150–400 °C. Material grades such as 38CrMoAlA (per GB/T 3077) are used, with nitriding as a common surface treatment. Tolerances are held to ±0.02 mm (ISO 2768-m) to ensure melt uniformity. Weight ranges from 50 to 500 kg depending on size and material. These values are reference ranges; actual specifications must be confirmed with the legal manufacturer or supplier for the specific model and application. The screw is a wear part; its lifespan depends on operating conditions and material selection. Regular inspection for wear, especially in the metering section, is essential to maintain product quality and prevent failure. Proper alignment and torque handling are critical during installation and operation.

Rotational motion generates shear heat to melt polymers while helical geometry conveys material forward under pressure. As the screw rotates, polymer pellets are drawn into the feed zone, where they are compacted and heated. The decreasing channel depth in the compression zone increases pressure and further melts the polymer. In the metering zone, the melt is homogenized and pumped to the die. The screw's design, including flight pitch and channel depth, determines the balance between shear heating and conveying efficiency. Operating parameters such as screw speed and barrel temperature must be optimized for the specific polymer to achieve consistent melt quality and output.