The three main functions of the screw, as shown in
Figure 5 are:
• Solids conveying – to collect the polymer pellets from the
feed-hopper and convey them forward along the barrel.
• Melting – to cause the pellets in the screw to be melted,
partly by shear heat and partly by applied heat.
• Metering – to compress and homogenise the melted
polymer and deliver it at a uniform rate to the die.
Figure 5: