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Most void is created
inside thick molding products because the inside part
cools and shrinks slow.
The resin freezes on the molding wall firstly, and cools
and shrinks to inside. In the process, the inner part
cools and shrinks more, and leaves void. |
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01. Lack
of Uniformity of product thickness |
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Maintain the thickness of molding
product uniformly and refrain from any
sudden change of thickness. |
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02.
Insufficient pressure in mold |
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Raise
the holding pressure and holding
pressure time. |
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03. Small
size of sprue, runner and gate
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Expand
sprue, runner, and gate. If they are
small, other problems may occur, such as
short shot, jetting, lower weld
strength, silver streak, etc. |
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04.
Pressure drop caused by flash |
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You
can prevent flash from occurring by
lowering the temperature of resin and
cylinder or the injection pressure.
However, it may cause short shot, sink
mark or void. Therefore, mold adustment
is recommended. |
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05.
Moisture (Void occurred out of center.) |
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If
void is occurred to other area, not
center, moisture might be the cause.
Therefore, dry resin and operate again. |
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06. Gate
structure |
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Change
the gate structure to tap gate. |
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07.
Multiple pin-point gate |
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The
use of multiple pin-point gate may cause
stagnant air in the center of product,
which may cause void and black spot. To
prevent any stagnant air, change the
location of gate and install the air
vent. |
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