Feed Zone The function of this zone is to preheat the plastic and convey
it to the subsequent zones. The design of this section is important since the
constant screw depth must supply sufficient material to the metering zone so
as not to starve it, but on the other hand not supply so much material that
the metering zone is overrun. The optimum design is related to the nature and
shape of the feedstock, the geometry of the screw and the frictional properties
of the screw and barrel in relation to the plastic. The frictional behaviour of the
feed-stock material has a considerable influence on the rate of melting which
can be achieved