The complex multi-piece elements are only four millimeters wide and 3 mm high. A silicone gasket with an injection weight of 0.02 grams is located on the upper end of the valve body, which is made of thermoplastic. This housing contains a thin metal memory wire that is required for the valve to operate. SMA stands for Shape Memory Alloy. When voltage is applied, the wire heats up and contracts, activating the SMA valve. If the current is interrupted, the cable cools down in fractions of a second and the valve closes. This controls the filling of the air chambers and therefore the massage pressure. bacobolts.yictic
The two polymeric materials are combined in one step using
the Engel e-victory 140 injection molding machine. Polyamide (PA) casings are
first injected into a rotating mold with 16 + 16 cavities. In the second
position of the turntable, Liquid Silicone (LSR) is injected directly, while 16
more main shells were produced at the time. PA and LSR form a chemical bond.
However, for safety reasons and since the contact surface is very small,
immediately after injection molding, the finished parts are annealed at 200 °
C. Thus, the thermoplastic and the silicone are firmly bonded. The parts are
then 100% quality controlled by a camera and immediately transferred to the
logistics department for shipment to the customer “who is the global market leader
in car seat massage systems,” he explains. Lehmann, Managing Director of Sei
Woo Hi-Tech Polymer GmbH. To date, Sei Woo has supplied over 200 million of
these components.
Zero waste
“Multi-piece injection molding reduces the risk of error,
which would be enormous if the micro parts were individually assembled,”
explains Lehmann, stressing: “The zero-error strategy is the cornerstone of our
success.” Sei Wu often works closely with the client during the product
development and optimization phase. The intake valves used in the seat massage
system are the best example of this. “This product was originally manufactured
by another company, but the number of defective parts was high,” says Lehmann.
“We redesigned it in concept and design, thus reducing the number of parts
rejected in the process to zero.” Thanks to extensive development experience,
attentive attitude to customer needs, and high flexibility,
The founding of Sei Woo in Austria in 2000 demonstrates that
the Singapore-based Sei Woo Group sees great potential in liquid silicone and
sees the future. LSR has been increasing its market share for many years thanks
to its exceptional stability and biocompatibility, as well as its ability to
efficiently process. Sei Wu, who specializes in microtechnology and multi-component
applications are seizing the opportunity to enter a new niche. Among the
smallest parts produced by Sei Woo to date are the O-rings for mobile phone
charging cables, a product that weighs several thousandths of a gram. “With
this product we have entered an area where the effect of gravity is canceled
out,” says Lehmann.
Consistent quality with competitive unit cost
These are mainly new applications that are driving the trend
towards smaller and smaller components in sectors such as automotive electronics,
mobile radio, acoustic engineering and medicine. By reducing the size of the
components, the requirements to be met by the injection molding process are
constantly increasing. “I can only offer our customers what the injection
molding machine and the mold allow me to remove,” explains Lehmann. Consistent
production processes, maximum reproducibility and precision are the
requirements that the Engel e-victory injection molding machine meets optimally
for air inlet valves. Thanks to the electric injection unit combined with the
columnless servo-hydraulic clamping unit, this type of machine combines
extremely high precision with exceptional economy. This is especially
noticeable in multicomponent applications. In a columnless clamping unit, mold mounting
plates can be used to the brim, and even large and bulky rotary table molds can
fit on a relatively small injection molding machine.
Sei Woo's state-of-the-art production facilities in
Holzhausen have 17 injection molding machines, including six multicomponent.
They all came from Engel in Schwertberg, just 50 kilometers from the hotel. The
team includes, in addition to the hybrid e-victories, which are used to
manufacture the intake valves, the Victory hydraulic machines and the
all-electric e-mac machines, which Sei Wu has invested in for medical
technology projects. A current example of this type of design is a pacemaker
across the joints.
All machines are fully automatic. “Without automation, we
wouldn't have a chance in Europe,” says Lehmann. "I do not offer our
customers sample parts until I am confident that we can produce them
automatically."