Preforming and In-mould Lamination in one Operation - Krauss Maffei

Decoration During Injection Moulding. Large-area, three-
dimensional laminated parts, such as boot linings have until now
been manufactured in multiple operations on vertical presses by
melt strand deposition. A new production method allows the
textile laminate to be preformed and injection compression lami-
nated (back injection compression) in the injection mould in a
single operation – with significant cost advantages.
I n
JOCHEN MITZLER
HENRY JANSSON
GEORG KAUFMANN
the automotive industry, cost pressures
are leading to permanent innovations
and developments. Manufacturers
of plastic parts and modules are
endeavouring to reduce the number of
process operations by, among other
things, combining different methods.
Tailored automation can also increase the
productivity of the manufacturing cell.
These are the aims that are also being
pursued by machine manufacturer
Krauss-Maffei, Munich/Germany, the
automotive subcontractors Collins &
Aikman, Skara/Sweden, and the mould
manufacturer Georg Kaufmann AG,
Busslingen/Switzerland, in an ongoing
successful joint project.
On an injection moulding machine, a
highly three-dimensional, decorated boot
Translated from Kunststoffe 3/2004, pp. 70–74
i
Manufacturer
Krauss-Maffei Kunststofftechnik GmbH
Krauss-Maffei-Straße 2
D-80997 Munich
Germany
Phone +49 (0) 89/88 99-0
Fax +49 (0) 89/88 99-3092
E-mail: info@krauss-maffei.de
www.krauss-maffei.de
Kunststoffe plast europe 3/2004
Fig. 1. Boot lining for a rear door of a new
vehicle generation (photos, except 5: Krauss-Maffei
Kunststofftechnik)
lining for a rear door (Fig. 1) is produced
by back injection-compression moulding
by the Decoform process patented by
Krauss-Maffei. The novelty of the process
is that the carpet decorative laminate does
not need to be preformed before it is injection
laminated on the injection moulding
machine. Automation plays a crucial
role in this.The integrated preforming only
becomes possible with the correct choice
of automation and precise interaction between
the individual plant modules.
Collins & Aikman have more than ten
years’ experience in low-pressure technologies.
The company produces pillar
and boot linings by the Decoform and
Decopress process. Collins & Aikman use
the vertical Decopress technology (back
compression) for the production of largearea
carpet-decorated side trim for the
boot. These parts have a relatively simple
three-dimensional geometry.
However, the design expectations are
higher for the development of new vehicle
generations. Designers require tighter
radii and more three-dimensionally complex
parts (Fig. 2). At the same time, an
AUTOMOTIVE • INJECTION MOULDING ■
Preforming and In-mould
Lamination in one Operation
identical or similar production concept is
used, in which a non-preformed carpet is
processed. During the development work,
the Decoform process developed by
Krauss-Maffei proved the ideal manufacturing
method for three-dimensional
parts. Back injection compression on an
injection moulding machine permits a
substantially wider processing window
and more flexible production than production
on a vertical back compression
press.
Production without Separate
Preforming
In the case of parts with a pronounced
three-dimensional shape, it was until now
Fig. 2. Side trim for the boot area of new vehicle
generations require tight radii and parts with
three-dimensional complexity
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■ AUTOMOTIVE • INJECTION MOULDING
Fig. 3. Compact production cell:
Krauss-Maffei Decoform series KM
420-3500DF injection moulding
machine with infrared radiator
bank and linear robot. The carpet is
preheated by infrared radiators
mounted above the mould
necessary to preform the carpet on a
thermoforming line, because otherwise
the carpet tears or the surface is damaged
by the pressing.
It is precisely this stage of separate preforming
that is eliminated by the new
Decoform manufacturing cell (Fig. 3). Instead,
the carpets are only formed in the
mould. To carry out this forming on the
injection moulding machine, infrared
radiators heat the carpets shortly before
processing at a suitable temperature before
they are immediately inserted by a
handling system in the mould. The mould
closes and the carpet is preformed by the
three-dimensional contour of the mould
core side.
To avoid wrinkles or cracks in the carpet,
a tensioning frame is installed
on the fixed side of the
mould (Fig. 4). Before the
core side penetrates into the
carpet, the decorative laminate
is clamped between the
movable mould side and the
tensioning frame. The pressure
forces exerted by the tensioning
frame determine the
slip of the decorative laminate
and must be matched to the
particular decorative laminate
used.
After preforming in the
mould, the actual back injection
compression process
takes place. In the Decoform
process, with the melt injection,
the mould opens by the
gap for the compression
stroke. The width of this compression
gap depends on the
decorative laminate and on the part
geometry. In this case it is between 5 and
50 mm. The gap is adjusted such that the
melt flowing in (polypropylene with
20 % talc) adheres to the side with the
decorative laminate. In addition, the material
still flowing in holds the melt cake
in balance, and prevents it slipping between
the mould halves. Then the mould
closing stroke compresses the melt in the
cavity.
The cavity pressure during compression
in the Decoform process is
below 70 bar. The relatively low pressure
can prevent damage to the decorative
laminate surface, such as ironing effects,
melt impressions, or compression marks.
Uniform Preheating with
Infrared Radiators
For the three-dimensional forming,
it is particularly important to
preheat the decorative laminate
uniformly to the correct temperature
over its entire surface. The
heat is transmitted from unscreened
infrared radiators. The
individual radiators can be controlled
so that – despite the high
chimney effect in the upper region
of the decorative laminate –
the temperatures are not higher
than in the lower region. The correct
temperature is essential for the uniformly
high quality of the part surface
(Fig. 5).
The radiator bank is mounted on the
machine directly above the clamping unit.
Because of its proximity, the handling sys-
Injection-compression mould
Fig. 4. Section through the mould with tensioning frame used in the Decoform
process
tem can introduce the carpet into the
mould within a few seconds after the heating
phase. This rapid transfer avoids cooling
of the carpet or tearing during the
compression stroke (Fig. 6). The preheating
takes place within the normal cycle
time.
Precise Handling
At the end of the cycle, the finished part
is removed at the moving half. At the
same time, a new preheated decorative
laminate is mounted on the tensioning
frame and fixed there with holding clips
(Fig. 7). The linear robots from Neureder
AG, part of Krauss Maffei Kunst-
Decoform
Melt strand
deposition
Cycle time + –
Protection of decorative laminate + +
Decorative laminates
and part handling
+ –
Machine investment + –
Mould investment – +
Reproducibility + –
Production flexibility + –
Footprint + –
Table 1. Comparison of the Decoform process with melt
strand deposition
stofftechnik GmbH, that are used handle
the complete insertion and removal in
less than 6 s. Thanks to the short removal
time, the machine is optimally utilised.
The robots and grippers are designed
for the specific process requirements
and were developed in close
collaboration between the
mould manufacturer and automation
specialists.
When feeding from the
magazine, the double gripper
only picks up a single piece of
carpet from the stack. For this
purpose, the carpet gripper
side is equipped with special
needle grippers. Pneumatically
driven needles pierce the
carpet and anchor like barbs
because of their angled position.
This prevents the carpet
detaching from the gripper
before it is preheated and inserted
in the mould. The part
pick-up side of the gripper is
equipped with vacuum suck-
ers, which grip the part from
the plastic side. Deposition on
a conveyor belt is implement-
2 © Carl Hanser Verlag, München Kunststoffe plast europe 3/2004

Fig. 5. Infrared micrograph of the preheated carpet (photo: GTT Willi Steinko)
ed by means of the C-axis on the linear
robot.
Summary
The most important benefits of the Decoform
variant described here is that it
completely dispenses with separate preforming.
Instead, the carpets are heated
with infrared radiators and transformed
into a three-dimensional shape directly
in the mould. The investment costs for
the entire process are therefore lower than
for preforming with a thermoforming
Temperature profile
Fig. 6. Heating and cooling behaviour of the carpets
line. In addition, the Decoform machine
requires a much smaller footprint compared
with similar decoration processes.
With the Decoform process, the logistics
overheads are reduced to a minimum.
There is no need to magazine and convey
preformed carpets.Provision of the carpets
at the machine is also greatly simplified.
Compared with in-mould lamination
by back compression moulding (meltstrand
deposition), the process is
characterised by greater reproducibility.
With the hot runner and the cascade nozzles,
the shot weight and weight distri-
AUTOMOTIVE • INJECTION MOULDING ■
bution are always constant. In the Decoform
process, the decorative laminate is
only mechanically stressed to a small
amount, since the melt pressures are relatively
low. The reduced logistics overheads
and improved process reliability
for the compression step result in greatly
reduced reject quotas compared with
melt-strand deposition. Another advantage
lies in the flexibility of the injection
moulding machine. By simple selection
of the injection compression side, the
machine can just as easily be used for
low-pressure technology as for standard
injection moulding.
Outlook
With this joint development, the project
partners have shown that a Krauss-Maffei
injection moulding machine with the
Decoform module can be used for the
reproducible and cost-effective production
of large-area three-dimensional
parts by in-mould lamination. This
technology will be used to an increasing
extent at Collins & Aikman in future.
Further parts with even more highly demanding
three-dimensional geometries,
such as door and boot side linings are already
at the prototype stage. In addition
to carpets, the Decoform process is also
suitable for TPO and PVC PP foam
Fig. 7. The double gripper almost simultaneously lays the preheated carpet in the
mould and removes the finished part
Kunststoffe plast europe 3/2004 3

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AUTOMOTIVE • INJECTION MOULDING
Project Partners
We are grateful to all project partners for
implementing the project:
■ Collins & Aikman, Skara/Sweden
■ Georg Kaufmann AG, Busslingen/
Switzerland
■ Krauss-Maffei Kunststofftechnik GmbH,
Munich/Germany
■ IWT Infrarot Wärmetechnik GmbH,
Altenstadt/Hessen, Germany
■ Neureder AG, Schwaig near Munich/
Germany
■ Dow Benelux B.V., Terneuzen/
Netherlands
■ GTT Willi Steinko GmbH, Nassau/
Germany
sheet, PVC leathercloth and textiles. The
process of graining in the mould developed
by Kaufmann and Krauss-Maffei –
reported on in Kunststoffe plast europe –
also offers new possibilities for surface
design. ■
THE AUTHORS
DIPL.-ING. (FH) JOCHEN MITZLER, born in 1973,
product manager at Krauss-Maffei Kunststofftechnik
GmbH, Munich/Germany, for new processes and
automation for injection moulding machines.
Contact: info@krauss-maffei.de
ING. HENRY JANSSON, born in 1957, is Engineering
and Development Manager at Collins & Aikman
Automotive Interior Systems, Skara/Sweden.
GEORG KAUFMANN, born in 1944, is owner and
managing director of Georg Kaufmann Formenbau
und Tech-Center AG, Busslingen/Switzerland.
© Carl Hanser Verlag, München Kunststoffe plast europe 3/2004