Appliance Design - February 2008 - (Page 44) JOINING ThrOuGh Thick aND Thin Typical SPr applications include (top photo) 1.20 mm aluminum/1.75 mm steel/1.20 mm aluminum; (lower right photo) 0.75 mm steel/1.00 mm steel/75 mm steel/2.00 mm steel; and (lower left photo) 2.0 mm plastic/ 2.0 mm aluminum. Self-piercing riveting joins dissimilar materials. by dean monday Dean Monday is sales and marketing manager at Henrob Corp., Novi, Mich. 44 applianceDESIGN February 2008 elf-pierce riveting (SPR) has been around for decades, so most are probably familiar with its basic premise. SPR is a cold joining process used to fasten two or more sheets of material by driving an engineered rivet through the top sheet(s) and upsetting the rivet, under the influence of a die, into the bottom sheet without breaking through it. What’s new is that, with a properly engineered system, SPR can produce high performance joints in diverse and thinner materials that are often used in today’s applications. Standard SPR can be used on materials 1.5 mm or 0.060 in. on a simple 2T joint. With more ductile materials, SPR can be used on joints down to 1 mm or 0.040-in. thick. In addition, special configurations can be designed for particularly demanding joints, such as the joining of a thick piece of plastic to thin metal or even plastic-to-plastic. Aluminum applications are common, as are those using stainless steel, pre-coated, pre-painted or pre-plated components. SPR has evolved since its humble begin- S nings, but still maintains all the benefits of the original technology. With SPR, no pre-punched/pre-drilled holes are required, and the process does not create a through-hole. No liquids or gases can pass through the resulting joint. This net-hole condition also adds stiffness to the product and provides better resistance to loosening. Unlike some mechanical fasteners, fall-out usually only occurs if the material immediately around the self-pierce rivet completely fails. SPR can easily join dissimilar materials, including aluminum, stainless steel, high-strength steel, and various plastics ranging from nylon and PP to SMC. SPR can be used on unprepared materials like pre-lubricated steel. SPR can also be used on pre-painted, pre-coated and pre-plated materials without secondary operations to improve appearance. For purposes of matching the joined materials, rivet heads can also be pre-painted, pre-coated and pre-plated. SPR can also be used on joints that include adhesives, sealants, or insulation. www.applianceDESIGN.com http://www.appliancedesign.com
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