Single-Screw Extrusion (SSE): Components & Principles

What is Extrusion?

A continuous process for producing shapes of constant cross-section by forcing a material through a shaped die

What is the primary goal of an extruder?

To convert a solid polymer feedstock into a homogeneous melt and pump it through the die at a constant rate and uniform temperature and pressure

What are the 3 zones of a single-screw extruder?

1 Feed zone 2 Compression plasticating zone 3 Metering zone

What is the function of the Feed Zone?

To preheat the polymer pellets and convey them forward. The channel depth is constant and deep

What is the function of the Compression Zone?

The channel depth decreases which compacts the material expels air and causes melting plasticating to occur

What is the function of the Metering Zone?

To homogenize the melt and supply the die with a material at constant temperature and pressure. The channel depth is constant and shallow

What is the function of the Breaker Plate and Screen Pack?

To filter contaminants from the melt remove the 'turning memory' of the melt and critically build up back pressure to improve mixing and melting

What is the typical helix angle $\phi$ for a 'square screw'?

17.65 degrees which arises from the pitch being equal to the screw diameter