Broad visibility with no stress
European premiere of a pioneering process
Rimsting/Meinerzhagen/Wixom/Bergisch Gladbach - For the first time in Europe, visitors to the Plastics and Rubber Fair in Düsseldorf will be able to see for themselves that large plastic car windows are no longer just a vision for the automotive industry. They can now be manufactured economically with the aid of the IMPmore® (In-Mould Pressing) process. Battenfeld Injection Molding Technology and Summerer Technologies will, together with Exatec, show in Düsseldorf how this innovative process can be used for the economical production of large-area plastic car windows made of polycarbonate. Until now, 0.5 m² was regarded as the limit for plastic windows, but the bar has now been raised to 1 m². The impressive production unit, which will be presented to the trade public, consists of a HM 20000/19000 injection molding machine with a 2-platen module, a special mould technology with a flap-hinged mechanism, and a KUKA robot.
IMPmore® (In-Mould Pressing) is a special variation of the parallel injection-compression molding process. It has been developed by Summerer Technologies and enables very large parts like roof modules to be produced in outstanding optical quality with very low internal stresses, where other molding processes would reach their limitations. Because of the special characteristics of the mold, it is now possible to operate large moulds with relatively low clamping forces and thus use smaller, cost-effective machines. In addition, a compensating process integrated into the mold neutralizes the high asymmetrical forces that are generated with one-sided off-center gating and negatively affect the service life of the mould and machine.
Summerer Technologies has made a name for itself as a specialist for all injection compression molding variants and has recently decided, after the positive market response to its products and services, to build a new plant near Rosenheim, Germany. Production line orders are already being dealt with there. Both the parallel injection-compression method and IMPmore® are combined with the two-component technology to give the customer additional scope for functional integration.
Injection-compression molding for stress-free parts
Plastic car windows must be virtually free of internal stress to ensure flawless coating and optimum weather stability and scratch resistance. The injection-compression molding process works at low pressure and has proved highly successful for the manufacture of low-stress parts. The IMPmore® process can further extend the benefits of parallel injection-compression molding.
Dynamic mould technique optimizes pressure profile
With the aid of a special flap-hinged mechanism in the mold, which generates a wedge-shaped compression gap, the pressure profile and pressure distribution in the mold are optimized during the filling and compression molding phases. It produces a very even and very low pressure profile during all phases of the cycle. Even with large dimensions like the car window (1,050 mm x 1,050 mm, wall thickness: 4 mm), a homogenous cavity pressure of below 200 bar is achieved across the entire part. This mold technique even allows the manufacture of windows with an area of up to 1.8 m² at the same wall thickness.
At the heart of the unit is the Battenfeld HM injection molding machine with a 2-platen module, which, because of its design and Unilog B4 control system, is ideal for this application. It is an injection molding machine for utmost precision, optimum accessibility and a small footprint. The 2-platen module is a design that, through its four moving tie bars in conjunction with a large platen area, is perfect for side mold assembly and the side take-off of bulky parts, as is the case with large car windows.
Special hydraulics are essential
A special hydraulic system has been developed specifically for the IMPmore® technology and the production of large-area glazing. The injection moulding machine has a pressure-intensified servo-hydraulic unit for the actuating cylinders in the mold to produce the flap motion of the mould. The cylinders are arranged in the upper and lower areas of the mould. To counteract any inclination of the machine platens due to the heavily off-center gating points and thus eliminate asymmetrical pressure patterns in the mold, Battenfeld has developed the so-called VFC-module® (Vector-oriented force control). During the entire process, the compression gap is measured at at least two points on the parting line. With this arrangement of the stroke transducer, the error factor of tie bar elongation is eliminated and it really is the actual compression gap that is measured. Differences in the measurements that indicate an inclined position of the machine platens are directly compensated in the control system via the machine's pressure transducers. This compensating mechanism balances out the load of the tie bars. The VFC-module® is recommended firstly for the parallel compression-injection moulding process, and secondly, when the VFC-module® is used in combination with the IMPmore® technology, the compensating hydraulic system can also be easily implemented in the IMPmore® mold.
Abrasion-resistant, UV-stable protection with Exatec® 900
Exatec, a joint venture of Bayer MaterialScience and GE Advanced Materials, continuously develops new functionalities for its proprietary Exatec® glazing system to meet the specific needs of transparent surfaces in cars.
Finished with Exatec® 900, the large-sized windows comply with the automotive industry's stringent demands regarding scratch resistance and UV resistance.
The extensive polycarbonate glazing system, Exatec® 900, offers car manufacturers and suppliers an opportunity to move into completely new dimensions in the vehicle window sector. Apart from the highly integrated backlites, this also includes demanding applications like panorama roofs and innovative door concepts.
Franz Josef Summerer
Tel. +49 (8039) 907670
info (at) summerer . de
Dr. Joachim Berthold
Tel. +49 (2354) 72469
Berthold.J (at) bmf.battenfeld . com
Exatec GmbH & Co. KG
Tel: +49 (2204) 842700
bprokop (at) exatec . biz
Quelle: Exatec Press Release 3/04 Broad visibility with no stress 18.10.2004