(1)Examples of application in the market
- Transfer roller for cigarette vending machine (DURACON KT-20)
The rollers were previously machined from metal rods to form the shape
of a screw. Therefore, there were problems of poor productivity and high
cost. On the other hand, there were also issues in the production by injection
molding, such as deformation and dimensional scattering above the specification
due to thick wall sections over all.
Now it becomes possible to obtain the rollers with excellent dimensional
accuracy by applying the GAI molding method, in shorter molding cycle time
compared with ordinary injection molding.
- Roof-rails entirely made of plastics (PC/PBT)
Roof-rails installed on the top of wagon-type cars are made of aluminum
in most cases for the balance of strength and light weight. In general,
the rails are formed by the drawing of aluminum sheets and the legs are
made by die casting of either aluminum or zinc. After that, both of them
are surface-teated and then assembled. The cost is high due to many parts
and processes required.
The new production process was developed by using GAI molding, under the
following prerequisites:
- Use of plastics
- Ordinary injection molding
- Reduction in the number of parts or one-piece molding
- Elimination of painting
By applying GAI molding, reduction by about 30% was achieved both in weight
and cost, compared with previous rails made of metal.
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(2)New GAI molding technology
- CGM technology(Controlled gas injection molding technology)
In GAI molding, a thick wall portion which is called a gas channel is designed
as means to introduce gas to the desired part of the flat molded product.
However surface defects such as flow marks, mottles, and the slipping marks
of grain caused by the change in wall thickness often appear on the surface
of the channel area, though their appearance depends on the design of moldings.
Therefore, CGM technology was developed to introduce gas to the particularly
desired position even within the uniformly thick portion. In this method,
thermal insulators are attached on the particular part of the cavity surface
which is corresponding to the desired position for gas introduction, so
that the resin can be kept molten there by the retarded cooling, in order
to facilitate the introduction of gas to the desired position.
- RFM technology (RP Topla floating molding technology)
In GAI molding, the passage of gas forms a hollow portion. Since the gas
whose viscosity is extremely low is injected into the highly viscous molten
resin in this process, it is very difficult to control the position of
the flowing passage of gas at bending portions or to form a hollow with
a uniform inner diameter.
RP Topla invented a method to solve the above mentioned problems. In this
method, a ball made of either steel or plastics, which is called a floating
core, is pushed through the molten resin by the gas pressure until it is
extruded into a dummy cavity.
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Gas Assisted Injection (GAI) Molding