Internationally, screw and barrel standards are mainly set by organizations such as ISO and DIN, while domestically, GB/T standards are followed. The following parameters should be considered when selecting a screw and barrel:
Screw diameter and length-to-diameter ratio (L/D): The diameter determines the extrusion volume, while the L/D affects the plasticizing effect. For general-purpose extruders, the L/D is typically 20-30; for highly filled or high-viscosity materials, an L/D ≥ 36 is required.
Screw speed range: High-speed extruders (such as those used for film production) can reach speeds of 600-1200 rpm, while large pipe extruders typically operate at speeds of 30-80 rpm.
Barrel heating method: Resistance heating is suitable for small and medium-sized equipment, while electromagnetic induction heating, due to its high thermal efficiency (over 90%), is gradually becoming the mainstream for high-end models.
Abrasion resistance requirements: The material is selected based on the abrasiveness of the material. For example, 38CrMoAlA nitrided steel can be used for ordinary plastics, while WC-Co coated screws are required for glass fiber reinforced plastics.
