This often sets the upper limit for output. The
screw cannot be run any faster because the
material is coming out with an “applesauce”
surface, with streaks, parabolic ridges, and
perhaps Particles of undispersed additive.
Screw modifications, such as pins or separate
mixing heads will help, but may raise melt
temperature. Running more slowly will always
help, as it provides more residence time. A
screw with internal cooling mixes better
because it has the effect of a shallower channel
in the metering zone. The output per rpm drops
30, but may be regained by increasing the
screw speed, unless melt temperature gets too
high or the drive system cannot safely run
faster. High pressure is good for mixing. A valve
will do this, or a gear pump pressure control
that can serve as a valve. Cooler dies increase
the resistance and thus raise the pressure in
the system. Finer screens will raise thepressure, but as they keep clogging, pressure
is inconsistent.