Modern Plastics Worldwide - July/August 2009 - dae uptlax

PROCESSING
TECHNOLOGY
Let the processing begin
How are parts formed? First the
pre-cut decorative material is
placed in the second cavity of the
open mold and fixed in place. The
mold closes and the decorative
material is preformed, while in the
first cavity the polypropylene (PP)
is molded and then cooled. When
the mold opens, the PP supporting
structure remains in the moving
mold half and the pre-formed
decorative material remains in the
stationary mold half.
The two halves of the open
mold are then repositioned by
means of a sliding table so that the
PP supporting structure and the
preformed decorative material face
each other. The mold then closes but a
gap remains between the halves. This
gap represents the thickness of the foam
layer and is determined by the geometry
of the second cavity; it is deeper than
the geometry of the first cavity by a
distance equal to the desired thickness
of the foam.
This gap is then filled with foam,
with either expandable TPE injected into
the gap via a gating system and diverter
mpw.plasticstoday.com
PROCESSING TRENDS
Here, shown in a 2-injection unit configuration, the
Varysoft slide-table mold lets processors get softtouch
foam exactly where it is needed.
mounted on top of the mold, or via the
PUR mixing head, docked against the
underside of the mold. Once foaming is
complete, parts can be de-molded and
any surplus decorative material can be
trimmed.
In another decorative development,
Kaufmann also says it can make injection
molds suitable for back injection
molding of metal films. Such films could
be thick enough to give the feel and
look of a genuine metal surface,
more so than with electroplating,
but without requiring a secondary
operation.
Here again, the process is deceptively
simple. The metal film is
placed and held in a mold in essentially
the same way as any other
decorative surface would be for
back injection molding.
With this development, any surface
structures machined into the
walls of the cavity (logos, for example,
or other decorative elements)
can be transferred to the molded
part (see photo, previous page).
While the mold is closed after injection,
an integrated punching tool
separates surplus film from the
molded part, but leaves the edges of the
film wrapped around the part to produce
a smooth edge.
Kaufmann says it already has formed
parts using aluminum and stainless steel
films and is testing other materials. The
moldmaker worked with the university
in Rappperswil, Switzerland on development
of the coupling agent necessary for
a reliable metal-plastic bond.
Coreless winding cuts transport costs, pleases Walmart
By Robert Colvin
New fi lm extrusion lines increasingly
include winding technologies
that either employ thin-wall paperboard
cores or even eliminate cores
altogether. Processors are set to
benefi t from the savings.
According to Dave Finnemore, VP sales
EMEA at Gloucester Engineering (Vienna,
Austria), the technology’s introduction
is being pushed by environmental
sensibilities. “The main aims behind
developing [film] products with thinner
cardboard cores or even with no core
at all are reducing costs or removing
the need for management and disposal
of the used cores, reducing waste taxes,
eliminating shipping and storage costs
by optimizing film meterage on a pallet,
and lowering production
costs,” he says.
Finnemore says
an estimated 350 million
cardboard cores
are disposed of annually
in Europe, Russia/
CIS countries, and the
Middle East. While some
Central European core
suppliers offer collection
systems for recycling,
in other regions such
schemes don’t exist. He
says global multinationals
such as Walmart, Coco-Cola, P&G,
and the Carrefour group are implementing
environmental policies for waste
reduction that foresee not accepting
Easycoreless shafts comprise up to 250 expanding and
contracting parts to produce stretch film without the
need for cores. Thin cores and standard cores can also
be produced.
hand- and machine-stretch pallet-wrap
film if the retailers have to dispose of
paperboard cores.
While resin costs for cast stretch-film
MODERN PLASTICS WORLDWIDE • JULY/AUGUST 2009 15