In the above two GAIMmethods, there are been still some
disadvantages such as exploding at molding by high pres-
sure gas, surface dimmed by mixed gas and melt, limitation
of gas nozzle design and slow cooling of molding. In these
disadvantages, slow cooling of the molding is one of the
most important things connecting with a cycle time of man-
ufacturing. The interior temperature of a hollow shape is in-
creased by the injected gas, and rises almost to the melting
temperature. The heated gas in the hollow shape acts like
a hot core that causes the molding to cool slowly. Conse-
quently, the cycle of GAIM process would be lengthened.
2. Reverse gas injection molding (RGIM)
In conventional GAIM process, hesitation marks have
been needed to remove. The material for injection molding
has been needed to reduce more and more. The gas in a
hollow shape acting as hot core has been needed to remove
for faster cooling of molding. For satisfying these require-
ments, we devised a new GAIM process, the reverse gas in-本文来自优%文~论!文\网，
毕业论文 www.youerw.com 加7位QQ324~9114找原文
jection molding, which was registered in Korea Patent No.
0286015. There are some special units that include an air
unit that is used to vent and remove the hot nitrogen gas in
hollow shape and the overflow buffer that is used to reduce
a material. Fig. 1 shows the schematic of the RGIM system.
The RGIM process is divided into four steps (Fig. 2). The
first step is filling. A melt injected from a hot runner fills
the mold cavity about 98–100% such as full shot method.
The second step is hollowing out the melt after a constant
delay time. A pressured gas is injected into the mold cavity.
The pressured gas makes a hollow shape. Synchronously,
the pushed melt that is still in a molten state in the middle of
cavity reversely re-enters into an overflow buffer. The third
step is holding. The pressured gas acts as holding pressure.
The last step is air blowing. Completing holding phase for a
few seconds, air is blown for a few seconds by the air unit to
cool the molding and to remove the hot gas in hollow shape.
We applied a cutter that automatically acts to vent hot gas
by the air unit.
In the RGIM process, there are two differences from the
traditional GAIM process. The first is that there isn’t the
physical overflow for the expelling of a melt. Instead of
expelling, the melt re-enters into the overflow buffer by the
injected gas while hollowing out the melt. This step saves
material. So, this new GAIM process was named as the
RGIM. The second is that there is the air unit in this system.
This air unit vents and removes the hot gas for faster cooling
in the hollow shape by air blowing.
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