Contamination-free vibration welding for use in green technologies

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MAHLE Filter Systems (MAHLE) designs and manufactures a wide range of under-the-hood components. MAHLE currently uses vibration welding (VW) technology to join injection-moulded thermoplastic components used in air-intake manifolds. In order to expand into the fuel-cell market, MAHLE must find a technical solution to reduce both the size and amount of particulate contamination generated during the welding process.VW involves bringing two thermoplastic components together under pressure. One part is prevented from any lateral motion while the other is oscillated laterally at frequencies of the order of 200 Hz over amplitudes of approximately 1 mm. In the initial phase of the process, Coulomb friction causes the temperature of the interface to rise, ultimately reaching the polymer's melting point. Once a melt layer is formed, energy is generated by viscous dissipation causing more melting. Molten polymer flows from the weld interface (referred to here as flash) and the two components move toward each other (referred to here as meltdown). This project will study the characteristics of the flash. The flash generated during VW is often brittle and can contain particles such as "angel hair" that can break off resulting in particulate contamination of the assembly. The fuel cell market has very strict requirements on the amount and nature of flash-like contamination. This project will determine the effect of thermoplastic material parameters, VW process conditions as well as the weld geometry on the characteristics of the flash. It will allow users to select material, process conditions and weld designs in order to minimize the formation of particulate flash. It will achieve this through laboratory testing, pilot and industrial-scale welding and process modelling.