This crew consists of three zones. The first zone which is 1/2 up the screw is called the feed zone it has a constant flight depth,which forces the material together and reads it a bear.
The second zone called the meltdown has a decreasing like depth which reduces the plastic volume this causes the plastic molecules to rub harder against each other plaster sizing the material the melt zone
leads to the third or metering zone. The metering zone has a constant flight depth much smaller than that of the feed zone.