Page 119 - Injection Molding Advanced Troubleshooting Guide
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12.4 Cooling 105
Figure 12.5 Spoke layout runner system for an eight-cavity mold
Figure 12.6 Nonworking attempt to minimize shear-induced imbalance
Another option for mold cavity layout that can improve imbalance is to add a hot
runner system that allows for groupings of four cavities at a time. In other words,
for an eight-cavity mold use a hot runner with two hot drops leading to two individ-
ual groups of four cavities. Note that there is evidence that hot runners will still
suffer from shear imbalance problems, but it is normally not as severe.
12.4 Cooling
If a mold is not being cooled efficiently cavities may be exposed to differential mold
temperatures. This can be a problem that seems to change over time if the mold is
not consistently watered. If additional lines are run jumped together the variation
in steel temperature can result in part differences. It is critical to ensure that the
