informations about the IKV

INSTITUT FÜR
KUNSTSTOFFVERARBEITUNG
Reactive Moulding –
Lightweight on a large scale
ENGLISH
IN INDUSTRIE UND HANDWERK AN DER RWTH AACHEN
In-situ injection moulding for reinforced thermoplastic parts
There are still a number of technological and economic problems hindering
the widespread industrial production of fibre-reinforced plastic parts.
Together with several partners from industry, the Institute of Plastics
Processing (IKV) in Industry and the Skilled Crafts at RWTH Aachen
University is currently carrying out research into the in-situ injection moulding
process. This process creates the basis for the fully automatic, reproducible
production of fibre-reinforced parts without the need for de-flashing.
With in-situ injection moulding, the impregnation of the fibre reinforcement
is carried out in the injection mould. Unlike the currently established resin
injection processes with thermosetting matrices, the project partners have
opted for a thermoplastic matrix for the in-situ injection moulding process.
The use of caprolactam in combination with an activator and a catalyst
allows polymerisation to take place in the mould to produce polyamide 6.
The caprolactam from LANXESS Deutschland GmbH can also impregnate
dense fibre reinforcements because of its extremely low viscosity.
Polymerisation yields a thermoplastic matrix, which has the advantages of
outstanding impact strength and low density. In addition, the part can be
later welded and recycled.
Combined processing process with high functional integration
The in-situ injection moulding process therefore offers a number of promising
approaches to serve the fast-growing market of fibre-reinforced composites
in automotive and aircraft design and the sports goods industry.
IKV and its partners chose a shin guard to demonstrate the performance of
the process. The shins are protected from injury by a hard fibre-reinforced
thermoplastic component, while a flexible thermoplastic elastomer (TPE)
component provides good wear comfort. The article is produced by the IKV
experts using a combination of two processes: production of the fibrereinforced component by the in-situ process, and subsequent
functionalisation by backmoulding with the TPE component. It shows the high
potential of the in-situ injection moulding process for the series production of
complex composite parts.
Innovative mould concept for production without the need for flash removal
The low-viscosity melt makes particularly high demands on the sealing
technology of the in-situ injection mould. To produce the pre-moulded part so
that there is no need for the de-flashing operation, a compression edge is
integrated into the mould to compress the inserted preform towards the end of
the flow path. In addition, an extra sealing concept with silicone seals ensures
process reliability. The in-situ injection mould, which is equipped with two
cavities, has a second parting line that serves to demould the runner. The two
pre-moulded parts that are connected via separation points can thus be taken
directly out of the mould and further processed without any additional step to
remove the flash. For in-situ polymerisation, mould temperatures of approx.
160 °C are required, making a complex mould temperature control system
necessary. To save energy, heat loss into the environment is reduced through a
comprehensive insulating arrangement.
Reactive Moulding – Lightweight on a large scale
Ready-made preforms
With the in-situ injection moulding process, ready-made preforms are
inserted into the injection moulding tool. The preform consists of multiple
layers of glass fibre fabric bonded together with a thermoplastic bonding
agent to produce an easy-to-handle composite. They are manufactured with
the help of a variothermal preform tool in which the individual fabric layers
are pre-consolidated under vacuum. The next step involves cutting the multilayer structure with a robot-guided ultrasonic cutting head to the final shape
in a 3D cutting process. Before the ready-made preforms can be further
processed, they have to be dried. The preforms produced in this way ensure
that the IKV research team can rely on unproblematical processing by the insitu process.
Production cell for the automatic production of FRP
At the heart of the production cell is a special injection moulding machine from
ENGEL AUSTRIA GmbH developed specifically for this process. The material
is fed into this machine as a two-component system. One component contains
caprolactam and an activator, the other component, caprolactam and a
catalyst. The machine has two screw plasticising units, which allow melting
and dosage of the two components. Subsequently, the two components are
mixed in a counterflow mixing head connected to the injection mould.
After polymerisation in the mould at a temperature of around 160 °C, the premoulded parts are, one after the other, backmoulded in a single-cavity mould
with the TPE flexible component on a second injection moulding machine. Fastaction pressurised water heaters from gwk Gesellschaft Wärme Kältetechnik
mbH produce the high mould temperatures needed for the in-situ process. An
extraction system removes any gaseous reaction products that may be
produced.
Two processes, one robot gripper
The two processing processes make different demands on the handling of
the pre-moulded and finished parts. First of all, a needle gripper picks up
the preforms and places them into the in-situ injection mould. After
polymerisation, heat-resistant suction grippers remove the two pre-moulded
parts and place them one after the other into the single-cavity mould. After
backmoulding with TPE, the handling system deposits the finished moulded
parts onto a conveyor belt. Special centring elements on the mould make
sure the robot gripper is centred during insertion and removal, and thus
ensure accurate positioning in the different moulds. Capacitive sensors on
the combined robot gripper guarantee process reliability in the handling
process.
Institut für Kunststoffverarbeitung (IKV)
in Industrie und Handwerk an der RWTH Aachen
Institute of Plastics Processing (IKV) in Industry and the Skilled Crafts at RWTH Aachen University
Prof. Dr.-Ing. Christian Hopmann
www.ikv-aachen.de www.ikv-colloquium.com
CONTACT:
Dipl.-Ing. Mathias Weber
M.Eng. Julian Schild
+49 (0) 241 80-93827
+49 (0) 241 80-93983
[email protected]
[email protected]
Robot gripper
ASS Maschinenbau GmbH, www.ass-automation.com
Colour masterbatch
Clariant AG, www.masterbatches.com
Ultrasonic cutting head
EM-Systeme GmbH, www.em-systeme.de
Production cell consisting of two injection moulding machines and a linear handling system
ENGEL AUSTRIA GmbH, www.engelglobal.com
TPE for the backmoulding process
Gummiwerk Kraiburg GmbH und Co. KG, www.kraiburg-rubber-compounds.de
Temperature control systems for the entire production cell
gwk Gesellschaft Wärme Kältetechnik mbH, www.gwk.com
Standard mould units and mould design
Hasco Hasenclever GmbH und Co. KG, www.hasco.com
Counterflow mixing head
Hennecke GmbH, www.hennecke.com
Waste air engineering for the in-situ unit
Keller Lufttechnik GmbH + Co. KG, www.keller-lufttechnik.de
Mould sensor
Kistler Instrumente AG, www.kistler.com
Caprolactam, formulation and process optimisation and sponsor of the mould technology
LANXESS Deutschland GmbH, www.lanxess.de
Fibre preforms
P-D Interglas Technologies AG, www.pd-interglas.com
Dryer
Piovan S.p.A., www.piovan.com
Design and construction of the in-situ and TPE injection moulding tools
Schöfer GmbH, www.schoefer.at