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Lightweight Construction

Thermal joining speeds up composite manufacture

A thermal melting process will allow the combination of metal and thermoplastic composites in the future. This could offer significant process benefits, especially in lightweight production.

12 Mar. 2018
Kai Tubessing
HMI-ID02-105kt_Fraunhofer
Thermal joining speeds up composite manufacture (Photo: Fraunhofer IWS Dresden)

At the Fraunhofer Institute for Materials and Beam Technology (IWS) in Dresden, a new way of joining metal and thermoplastic to create a bond between the materials has been developed with the HeatPressCool integrative process (HPCI). In industrial applications, the process allows production cycles to be accelerated due to elimination of the laborious adhesive process. The lightweight construction industry in particular could profit from this, as the institute has demonstrated in a series of tests with organic fiber-reinforced thermoplastic sheets and metal cover plates. The process is also reportedly easy to automate and possible to integrate into existing Industry 4.0 environments.

Pre-treatment is crucial to the success of the process: the metal component is prepared and cleaned using laser ablation to a structural depth of 100 µm and at a rate of 30 cm2 per second to ensure the surface is free of impurities. The thermoplastic and metal are heated in separate processes. This subsequently allows the melted plastic to penetrate the fine structures of the metal more easily and improves adhesion; a joining gun is used to press the two materials together. Attention was paid to robot compatibility even during tool development, with the result that the production process offers the most modern process automation options possible. Previous approaches to joining different components in lightweight construction, such as the Fronius cold metal transfer process (CMT) , were primarily limited to joining different metals such as steel and aluminum.