Foam molding can be divided into 3 groups
based on the foaming ratio.
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Low-extent foaming
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Foaming rate : 1.01 - 1.05 |
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Medium-extent foaming |
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Foaming rate : 1.05 - 1.50 |
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High-extent foaming |
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Foaming rate : 1.50 - 3.00 |
The content of foaming agents and molding
method are somewhat different for each group.
Roughly speaking, low-extent foaming is suitable for solving
the issues of sinkmarks or deformation of ordinary moldings,
and high-extent foaming is useful for the purpose of thermal
insulation, reduction in weight, damping, and cushioning.
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In any group, ordinary injection molding machines
and molds can be used as they are.
In low-extent foam molding, full-shot method which is entirely
the same as ordinary injection molding is used. The dwell pressure
is also the same as in ordinary injection molding. The foamed
cells are generated only in the thick-walled areas of slower
solidification or in the areas of locally high mold temperature,
if any , and so sinkmarks and deformation in these areas are
reduced. |
(Full shot method)
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In medium- or high-extent foam molding, the short-shot molding
method is used, where the forward movement of the screw is stopped
before the cavity is fully filled. After that the cavity is
further filled by foaming pressure. Since there is no dwell
pressure, foamed cells are freely generated and the foaming
ratio increases accordingly. |
(Short shot method)
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The data shown in this home page
are based on our accumulated experience and laboratory data,
and not always directly applicable to your products used under
different conditions. Therefore, we can not guarantee that the
contents of this home page are directly applicable as they are
to the specific condition in our customers, and we appreciate
your final decision on the use of these data.
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