Kai Fischer

Spaltimprägnierverfahren für schnellere Herstellung von Hochleistungsbauteilen

Der breite Einsatz von endlosfaserverstarkten Kunststoffbauteilen mit hohen Faservolumengehalten wird durch die relativ langen Zykluszeiten der verfugbaren Fertigungsverfahren eingeschrankt. Dieser Beitrag beschreibt, wie sich durch die Entwicklung neuer Prozessketten die Produktivitat steigern lasst. Das Spaltimpragnierverfahren ermoglicht die Impragnierung von Bauteilen mit strukturellen Eigenschaften in wenigen Sekunden. Dadurch lassen sich hochreaktive, schnell aushartende Harzsysteme bei konstant hoher Formwerkzeugtemperatur verarbeiten, deren Einsatz bisher nicht moglich war.

Flexible Production of Thermoset FRP Components

Automation for Small Series Production Endless Fiber-Reinforced Plastics (FRP) are used in a wide variety of applications due to their outstanding potential for lightweight design. The production scope ranges from large series applications to manual, individualized parts with lot size one. The production of FRP parts in general is influenced by the increasing diversification and individualization of products. This desire for individualized production at low prices presents manufacturers with challenges in the areas of product development, process f lexibility and cost efficiency. Looking at the current FRP market, it becomes clear that despite the high growth rates in the field of thermoplastic reinforced

Approaches for increasing process rate of local 3D laser decoating for series production of hybrid composites

Laser structuring of tool surfaces with circular spots and diameter below 30 μm as well as laser decoating with line spots above 50 mm are established in industry. For the fulfilment of processes with intermediate requirements, e.g. local laser pretreatment on 3d surfaces of carbon fiber-reinforced plastics (CFRP) for subsequently intrinsic joining, an established technology is missing. Attuned robot and scanner systems with high flexibility and sufficient accuracy, as well as application oriented path programming and a methodology for shorting cycle times are missing. A new integration approach enables for the first time an overlapping workspace of injection molding machine and robot-guided 3d laser scanner for in-mold processing, adaptable to a wide range of polymer processing machines worldwide. Large-area surface processes at components with a production volume >30.000 pc./a require efficient path generation and processing. Supplementary to the 3d segment process developed by Fraunhofer Institute for Production Technology IPT tools are developed for scalable robot-guided decoating process. With respect to scan field size and angle of incidence a software is set up, which inherently allows a free implementation of genetic algorithms for finding a sufficient solution with the minimal number of scan fields and the corresponding optic positions. Furthermore, process optimization is done by a systematical analysis of resin ablation and heat affection using NIR short pulses at single spots, lines and rectangular. The conflicting objectives of increasing adhesive strength and decreasing cycle time for the specific FRP application is analyzed and quantified.

Improving accuracy of robot-guided 3D laser surface processing by workpiece measurement in a blink

A double-beam deflection unit (scanner) with integrated on-axis sensors for distance and temperature measurement is developed for the production of structural hybrid composite parts. This robot-guided 3d laser scanner is integrated in a composite production cell for in-mold laser pretreatment for subsequent joining. A basic challenge of industrial laser applications - the placement problem of workpiece in workspace of robot - was solved using on-axis low-coherence interferometry. Varying positions of workpiece for remote laser processes can in the future be compensated in seconds, depending on beam characteristic, here with a theoretical accuracy of 60 μm (X,Y), 1 μm (Z), 0,003° (B,C) and 0,174° (A). Two issues reduce this theoretical accuracy in practice. However, the improvement of daily process preparation is significant and validated by measurement of accuracy of laser path image at a close-to-series carbon fiber reinforced plastic (CFRP) demonstrator of BMW. The optimal position of scanner relative to part is a fundamental condition for ablative 3d surface processing. Driven by the necessity of quality assurance within automotive industry the inherent potential of sensor technology is shown, additionally. This potential study gives impulses for further developments of multifunctional laser scanners.

Compression moulding of LFT components with increased quality by variothermal mould technology

For the production of composite components made of long-fibre reinforced thermoplastics (LFT) the economic compression moulding process is well established. However, the low temperature of the compression mould during processing leads to a significant increase in both the material viscosity and in the compression force in particular for thin-walled components. In addition, low surface qualities result which prevent the application of such components in visible areas. To overcome these disadvantages, a variothermal compression moulding process has been developed at the Institute of Plastics Processing (IKV) at RWTH Aachen University. With the variothermal mould technology a reduction of the viscosity of the moulding compound during processing is achieved. This results in a reduction of compression force by about 60 %. Additionally, moulding compounds with higher fibre contents (up to 60 % by weight) can be processed and the surface quality of LFT compression moulding components can be significantly increas...

Quality Controlled UD Tape Production for the Individualised Production of Load Optimised Thermoplastic Composite Parts

A flexible and individual component manufacturing process for thermoplastic composites (TPC) has been developed at the Institut fuer Kunststoffverarbeitung in Industrie und Handwerk an der RWTH Aachen (Institute of Plastics Processing (IKV) at RWTH Aachen University). The process consists of a quality controlled tape production and a combined forming and joining process with additive manufactured functional structures. This paper describes the requirements for the unidirectional (UD) tape properties and the quality controlled tape production line in order to allow for a flexible and individual component manufacturing of load optimised thermoplastic composite parts. Besides the UD tape geometry and fibre impregnation quality an even fibre distribution over the width of the UD tape is an important characteristic. Results of investigations regarding the online measured quality data (fibre distribution) and offline measured UD tape properties (local fibre weight content) are presented and discussed.

Mold technology for mass production of continuous fiber-reinforced sandwich parts

Abstract In order to reduce cycle times, increase functional integration and automation further, the innovative gap impregnation process and mold technology was developed at the Institute of Plastics Processing at RWTH Aachen University (Germany) in collaboration with industry partners. The novel process enables an automated production of continuous fiber-reinforced sandwich composite structures in integral design with high surface quality in short cycle times, which is demonstrated by manufacturing a carbon fiber-reinforced plastic (CFRP) engine hood. For the first time, the gap impregnation and mold technology makes it possible to manufacture large-scale, three-dimensionally shaped sandwich components in one shot and in short cycle times at similar mechanical properties compared to the reference steel hood. Furthermore, a weight reduction of about 60% to only 5 kg was achieved for the CFRP engine hood. This paper focuses on the systems engineering of the RTM-related gap impregnation process. The focus is on the utilized mold concepts for the pressurized air-assisted ejector pins, vacuum-tight sealing, the motion concept of the mold halves, resin traps, sensors for process control and the specially treated mold surfaces for class A surface components. Additionally, the main procedures, capabilities and characteristics of this innovative process are discussed.

Großserienproduktion struktureller endlosfaserverstärkter Kunststoffbauteile

Um endlosfaserverstarkten Kunststoffbauteilen den Zugang zum Massenmarkt zu ermoglichen, mussen ihre Produktionskosten deutlich reduziert werden. An der RWTH Aachen haben sich das Institut fur Kunststoffverarbeitung (IKV), das Institut fur Textiltechnik (ITA) sowie das Fraunhofer-Institut fur Produktionstechnologie IPT zur Forschergruppe FOR 860 zusammengeschlossen, um neue, grosserienfahige Prozessketten zur Herstellung solcher Kunststoffbauteile fur strukturelle Anwendungen zu entwickeln.

Mass Production of Fibre-reinforced Plastic Components for Structural Applications

The production costs of fibre-reinforced plastic components must be significantly reduced before such components can enter the mass market. At the RWTH Aachen University, the Institute for Plastics Processing (IKV), the Institute for Textile Technology (ITA) and the Fraunhofer Institute for Production Technology (IPT) established the FOR 860 group of researchers, with the aim of developing new process chains that would allow the mass production of such plastic components for structural applications.