JEC COMPOSITES MAGAZINE - Issue #45 - November/December 2008 - 51

Induction the component, and a qualitative temperature gradient in the laminate. Fig. 4: Continuously welded bumper support (GF/PA6) (a) Seam types, (b) Welded part, (c) Cross section. Fig. 2: Process conduct for 2D induction welding (schematic/qualitative). Automated process The standard 2D induction welding process is limited to flat joints. A recent research project enhanced the standard process and adapted it to an industrial robot system. Thanks to this newly developed three-dimensional welding process, complex and curved parts can be joined with a high degree of automation and a quality control system. In contrast to the two-dimensional process, it is the components to be joined that are fixed, and the mobile welding unit is guided by a robotic system. Large and heavy components can thus be welded using a suitable handling system such as articulated or gantry robots. The surface temperature of the component is measured continuously for weld quality control, and the temperature profile is used to indicate quality problems, e. g. insufficient heating or gaps in the welding susceptor. An example of induction-welded, aviation-certified material is presented in Figure 5. Here, the T-stiffener was joined from two thermoformed L-profiles. The cross-sectional morphology shows a homogeneous bond line of good quality. Fig. 5: Microstructure of discontinuously induction welded T-joint (CF/PPS). Conclusion and outlook Robotized induction welding of thermoplastic fibre-reinforced composites was successfully adapted to an industrial robot. The system is capable of welding different materials and geometries. A quality control system is integrated, allowing continuous quality evaluation and process documentation. The compact design and the use of an automated handling system allow a reproducible production of complex geometries with curved seams that are difficult to weld with other technologies. The weld is produced sequentially by a generic tool, so that product variants can be produced by reprogramming the system without the need for re-tooling. This is advantageous for components with numerous variants and short product life cycles. Future work will include process modelling and the development of enhanced welding susceptors. More information: www.ivw.uni-kl.de Fig. 3: Robotic induction welding system: (a) Overview, (b) Welding unit. Figure 3 (a) shows the robotic welding system and Figure 3 (b) shows the main elements of the welding unit, that integrates the heating and consolidation steps. For continuous joints, rollers are used. In case of spot welds, these can be changed to stamp tools. The system can weld different joint configurations. If the components to be joined are supported by a surface, only the upper consolidation roller is used. When there is no direct support, a second roller is available as counterpart. These different consolidation modes allow welding in positions that are difficult to access. An example can be seen in Figure 4. The bumper support is joined from two thermoformed half shells, showing different seam types. Acknowledgements The authors would like to thank the partners within the project “Wirtschaftliches Fügen von Faser-Kunststoff-Verbundstrukturen mittels induktiver Erwärmung unter Einsatz flexibler Handhabungssysteme”: BondLaminates GmbH, Brilon, Jacob Composite GmbH, Wilhelmsdorf, KUKA Systems GmbH, Augsburg, Institute for Manufacturing Technology and Production Systems, University of Kaiserslautern, all from Germany. This work was supported by the Bundesministerium für Bildung und Forschung (BMBF) within the project “Forschung für die Produktion von morgen” (02PB2030) and is supervised by Forschungszentrum Karlsruhe (PTKA), Bereich Produktion und Fertigungstechnologien (PFT). No45 November-December 2008 / jec composites magazine

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JEC COMPOSITES MAGAZINE - Issue #45 - November/December 2008

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #45 - November/December 2008