Plastics Engineering - May 2014 - (Page 9)
Multi-Process Composite Molding
The commercial Varysoft part for Kia, however, is different.
It's made with two other processes besides injection molding. The soft-touch TPO surface is no longer injected, but
vacuum-formed. It starts with TPO film, heated with an IR
heater built into the central rotating mold, then vacuum
formed to give surface texture. separately the fiber-glass-filled
ABs/Pc substrate is injection/compression molded using
Mucell microcellular foam, which shortens cooling time,
uses about a third less clamp force, and saves about 10% in
material. The TPO skin and ABs/Pc substrate are brought
together in the rotating mold, and the space between them
is filled with a shot of PUR foam. Foam is injected with RTM
equipment from Hennecke gmbH in st. Augustin, germany,
so the process combines vacuum-forming, thermoplastic
injection molding, and RTM foam.
At K 2013, Engel showed a combination of RocTool induction-heated molds and a carbon-fiber-reinforced lightweight
construction in molding a case for an electronic tablet. The
process started with pre-pressed, woven-carbon-fiber sheets,
then over-molded them with high-gloss methyl methacrylate
ABs. Rapid heating in RocTool's induction mold creates a high
gloss piano finish even over woven fibers without surface
coating.
Another interesting multi-process fiber composite is a
continuous fiber reinforced PA6 seat pan molded for a 2013
Opel Astra sedan by Reinert Kunststofftechnik gmbH
in Bissingen an der Teck, germany. It combines two
processes. First a precut continuous glass fiber insert preimpregnated with nylon is heated with an IR heater inside the
mold and preformed. Then the mold closes, and the prepreg
is over-molded with short-glass-filled PA6 to fill out the part
geometry. The composite replaces a stamped steel part, at
half the weight.
"
with two and three shots of clear Pc with dark Pc frames and
integral channels.
Other multi-shot automotive parts began to use rapid
induction heated molds from RocTool s.A. in le Bourget du
lac, France, and Mucell microcellular foam from Trexel Inc.
in Wilmington, Massachusetts, UsA, to produce glossy
foamed parts in one step, like the cover for an automotive
entertainment system molded on an Engel press by groupe
Plastivaloire, langeais, France, for Johnson controls gmbH
in germany.
RocTool's rapid induction heated molds are also used
with Mucell microcellular foam in multi-shot production of
a BMW 320 dashboard air vent control part, molded by Fischer Automotive systems gmbH in Horb am neckar,
germany. The unpainted part combines matt and high gloss
surfaces, normally not possible with a foamed part.
Then automotive molder georg Kaufmann Formenbau Ag
in Busslingen, switzerland, developed a process called
Varysoft with Engel to make a complete soft-touch instrument panel for partner Hyundai-Kia Automotive group.
When Kaufmann showed Varysoft for the first time at an
open house in 2010, the process had three thermoplastic
shots: glass-filled ABs/Pc substrate followed by foamed
TPE and soft touch TPO surface. The concept made a complex finished part, but the steps were still thermoplastic
injection molding.
Individually these
technologies aren't
new... But putting them all
together into one
automated, high-volume
machine
is new.
"
How far is multi-process molding prepared to go in the
future? At K 2013, the Institute of Automotive Engineering of
RWTH Aachen University in germany showed a developmental combination of directional long fiber with in situ
polymerized PA6. That wild idea was the subject of a PhD dissertation in 2011 by lars Fredrik Berg, whose dissertation was
chaired by the Fraunhofer Institute of chemical Technology
IcT in Pfinztal, germany, and co-chaired by Professor georg
steinbichler, head of research and development at Engel.
Berg used two equal-sized injection units for separate
plastification of caprolactam melt with activator and with catalyst. He also developed a special mixing nozzle to combine
the two caprolactam melts just before injection into the
mold and a modified non-return valve to process ultra-low
viscosity melts accurately. The demo at K 2013 molded an athletic shin guard to show the process. First a preform of dry
aligned fibers was inserted into the mold cavity. Then the liquid caprolactams were combined and injected into the cavity
without disturbing fiber position.
After Berg's dissertation was finished, Engel continued
the R&D, tuning the technology to use a standard injection
molding machine. The concept is similar to fiber-reinforced
RIM, in which a mold is filled with liquid RIM ingredients, without disturbing the fibers, and then cured. But in situ
polymerized glass-filled PA6 is a thermoplastic, not a thermoset, so scrap can be reused. The target market is
high-volume thermoplastic composites for automotive.
www.plasticsengineering.org | www.4spe.org | MAY 2014 | PlAsTIcs EngInEERIng |
9
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Plastics Engineering - May 2014
Table of Contents for the Digital Edition of Plastics Engineering - May 2014
Contents
Plastics Engineering - May 2014 - Cover1
Plastics Engineering - May 2014 - Cover2
Plastics Engineering - May 2014 - Contents
Plastics Engineering - May 2014 - 2
Plastics Engineering - May 2014 - 3
Plastics Engineering - May 2014 - 4
Plastics Engineering - May 2014 - 5
Plastics Engineering - May 2014 - 6
Plastics Engineering - May 2014 - 7
Plastics Engineering - May 2014 - 8
Plastics Engineering - May 2014 - 9
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Plastics Engineering - May 2014 - Cover3
Plastics Engineering - May 2014 - Cover4
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