Overheating may limit the rate if the take-off
cooling is limited, or it may produce
degradation or make dimensional control and
sizing difficult. In such a case, stop all barrel
heat except in the rear zone as needed for
bite (input) control and cool the barrel if
necessary. (In a few cases, more barrel heat
will yield a cooler melt.) There is a
temperature below which the melt will not go
at a given screw speed, even if all the barrel
heaters are turned off.
See if the controller around 70% down the
barrel is overriding. This means over packing
of the metering zone—overbite—with much
heat generated at the entry to that zone. In that
case, reduce the bite by changing the feed
temperature, rear barrel temperature, or
particle size.
Stop all barrel heat except in the rear zone
as needed for bite (input) control and cool
the barrel if necessary.