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New fastener can solve conductivity issues in bonded lightweight assemblies
Story added July 2014
Driven by lower emissions and increased economy, lightweight vehicle assembly developments will inevitably create challenges for traditional techniques. Automotive OEMs are reducing vehicle weights by bonding thin sheet aluminium and whilst effective, this can create issues if electrical continuity needs to be maintained, but gets broken by the wafer thin sheet of glue between the metal sheets.
One solution is to ‘drive’ stainless steel fasteners through the sheets simply to reintroduce electrical pathways. However, the prerequisite of a pilot hole for each fastener makes this short-term solution time-heavy. EJOT UK has overcome this by utilising fastening technology originally developed for the company’s Construction Fastenings portfolio. Innovative twin thread geometry that displaces metal rather than cut it, was adapted – making it possible to reduce debris whilst generating faster installation speeds. More significantly the screw is manufactured with a ‘pierce-point’ tip which eliminates the need for a pilot hole – significantly shortening installation time.
Normally zinc plated fasteners require an organic coating to increase the corrosion resistance and to speed up installation. Adding an organic coat also drastically reduces conductivity by acting as an insulator. EJOT’s Applitec R & D team have found that adding Nickel to the Zinc plating successfully maintains electrical conductivity and comfortably achieves the 720 hours salt-spray testing requirements.
The resulting product has been named the EJOT E-connectivity fastener and is currently being trialed by several OEMs with an interest in light weight assembly processes.
Article first published in FAST Magazine, Summer 2014Back to News Page