Figure 8. Effects of (a) feed rate
and (b) screw rotational speed on the temperature of the kneading
section. The screw rotational speed was set to 88 rpm to determine the
effect of the feed rate. The feed rate was set to 1.0 kg/h to determine
the effect of the screw rotational speed.
The effects of the feed rate and the screw rotational speed are shown in
Figure 8. The simulation results showed a higher temperature than the
experimental results. Their average discrepancy was 1.6 °C. The
numerical simulation tended to be at a higher temperature because the
temperature sensor was not immersed in the resin; it was located in the
barrel at a distance of 1 mm from the resin. The experimental data
involved the effect of heat resistance of the barrel so that the
temperature of the simulation was higher than that in the experiment.
The resin distribution on the twin screws in the numerical simulation is
compared with that from the experimental result. The experimental result
was obtained by capturing an optical photograph when the TSE stopped,
and the screws were pulled out from the barrel. As the resin used is
polypropylene—a semi-crystalline polymer—the color of the area
filled with the resin was white.
Figure 9 shows the optical photograph of the resin distribution and the
contour plot of the numerical simulation result. The numerical
simulation indicates that the resin exists on the pushing side of the
full-flight screw and the kneading section. The trailing side of the
full-flight screw is empty. The area where the resin exists in the
experiment corresponds to that in the simulation. The resin distribution
observed in the experiments and simulation agree well qualitatively.