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| 1.Principle |
DSI is a new molding technology
developed by Japan Steel Works, Ltd. to injection mold
hollow moldings or laminated structures. It contains 2 processes
of DSI-2M and M-DSI. In DSI-2M, one of
the initially molded half portions of a hollow molding is slidden
together with the movable half of the mold so as to be fitted
with the other half remaining in the fixed half of the mold,
and then they are joined together by secondary molding around
the fitted area after the mold is closed. In M-DSI, 2
kinds of resins are laminated to form solid structure.
The mold must have a sliding mechanism driven by a hydraulic
cylinder. The injection cylinder is equipped with either 2 heads
for 2 kinds of materials or one head for just one material.
It is necessary to use special injection molding machines, in
which respective molding conditions for primary and secondary
molding can be set, and also the control of hydraulic operation
for die-sliding, slidecores, etc, is possible. |
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| (1) A case and a cap are molded
by the injection from the "A" cylinder shown in green
in the figure. |
(2) The mold is opened, and the
cap remains in the fixed half of the mold while the case moves
to the movable half of the mold. The
sprue and the runner drop out of the mold. |
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(3) The movable half of the mold
containing the case slides so as to fit the case with the cap
by the mold clamping. Then the case and the cap are joined together
with the molten resin injected from "B" cylinder shown
in red in the figure. |
(4) The mold is opened, and the
products as well as the sprue and the runner are ejected. |
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| 2.Characteristics and effect |
- Post-molding processes such as adhesive
joining and assembly are not required.
- Controlling wall thickness is easy compared
with blow molding or GAI molding.
- Surface appearance and dimensional accuracy
are excellent.
- Higher design freedom. Namely, one-piece
molding, or installation of ribs and bosses inside the hollow
is possible.
- This process is applicable even if the
joining surface is three-dimensionally uneven
- Such post-molding processes as required
for lost-core process or blow molding are not necessary
and so the reduction of manpower is possible.
- Assembly or encapsulation molding becomes
possible by installing inserts inside the hollow.
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| 3.Points for consideration in designing products and molds |
- The accuracy in the movement and the positioning
of die-sliding is very important.
- It is necessary to elaborate a sure means
to keep the cap portion in the fixed half of the mold during
the initial molding.
- Means to facilitate mold release are required
for secondary molding.
- Since the secondary moldings are in the
form of a ring, runners and gates should be designed accordingly.
- The design of butt fitting between 2 portions
made by the initial molding is desirable.
- The shape of the joining portion such
as the width and the depth of the flow path, and the welding
bead is very influential in hermetic sealing.
- Thermal insulation in the joining portion
is necessary.
- Measures to prevent the generation of
weldlines such as vents, overflows, etc. are also necessary.
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4.Resistance of joints made of our materials
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to internal
pressure
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The joining characteristics were evaluated
by using the trial mold shown below. Our materials DURACON,
DURANEX and FORTRON, all of which are crystalline engineering
plastics, showed sufficient joining characteristics and
their application to various items is expected.
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Outline of molding conditions
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Cylinder temperature
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Mold temperature
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DURACON
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200  |
80 |
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DURANEX
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250 |
80 |
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FORTRON
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320 |
150 |
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| The pressure test was conducted
by using the moldings shown below. |
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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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DSI (Die slide injection molding)