Figure 6: Simulation results for the fixed core (from top):
final deformation of the core; thickness of the moldings,
injection side; thickness of the moldings, opposite side; and
warpage of the moldings
Figure 7: Simulation results for the one-sided constraints of
the core (from top): final deformation of the core; thickness
of the moldings, injection side; thickness of the moldings,
opposite side; and warpage of the moldings
One-sided constraints of the core
Predictions for the one-sided constraints of the core are
shown on Figure 7. the increased deformation of the core
caused even larger changes in the wall thicknesses that
now vary between 0.12 and 1.77 mm. Warpage also increases up to 1.5. the difference is caused by one-sided constraints
allowing some separation between the mold wall and the
core, as shown on Figure 8. this separation allows the core
to rotate slightly at the supports, thus making the supports
weaker.
Discussion of the case study
the case study clearly shows a significant effect of onesided constraints of the core on predicted quality of moldings,
even for the cases very similar to two-sided constraints.
While we can imagine that predicted for the fixed core constraints lowering down of the minimal wall thickness to 0.3
mm would be acceptable for some moldings, predicted for
the one-sided core constraints lowering down of the minimal
One-sided constraints with a gap
Predictions for the one-sided constraints with a gap are
shown on Figure 9. the gap between the core and the mold
makes the rotation of the core at support easier, and so it
additionally weakens the supports. the wall thicknesses
now vary between 0.08 and 1.8 mm. Warpage also slightly
increases.
Figure 8: One-sided constraints allow some separation
between the mold wall and the core (predictions for final
core displacements; one-sided constraints on the core).
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Plastics Engineering - May 2014
Table of Contents for the Digital Edition of Plastics Engineering - May 2014