Fasteners and Sealing
Southco claims a leading position in the supply of equipment to tackle the access demands of this growing automotive sector with its range of Dzus quarter-turn fasteners, which offer an effective replacement to conventional threaded fastening devices and meet the underbody and protective shield requirements of today’s cars and trucks.
Resistance to vibration
The key benefits of Dzus quarter-turn fasteners include resistance to vibration, fatigue and temperature changes, resistance to corrosion, and the choice of a variety of head style options. And Dzus fasteners can be simply secured to steel, aluminium or composite chassis underbody components through pre-punched holes. Ulrike Sturman, industry marketing manager for
transportation at Southco, explained: “There is a perpetual contrast between fasteners based on traditional screw thread systems and those based on quick-release mechanisms. It has long been perceived that, for a robust and durable fastening system, threaded fasteners offer the most cost-effective solution.”
Although a threaded system might be cheap to buy, the
time it takes to lock and unlock the system makes it expensive in terms of initial installation. “The recovery gains of the Dzus quick access quarter-
turn system, made from reducing the time it takes to install and then from future access needed for servicing more than outweighs the upfront investment,” Sturman added. More recently, the company has developed a range of
new quarter-turns and accessories. These include a stud that has an orientated head feature to cam. This brings the added benefits of the head feature always engaging and locking in the same position. The lock position of panel fasteners can therefore be identified, and installation time is speeded up.
Self-piercing technology
Moving away from steel panels does present an assembly challenge for motor manufacturers as spot welding, possibly the most common joining technique used in car assembly, is at best problematical when assembling light alloy or composite materials. An alternative system to replace welding of lighter
materials is the self-piercing rivet (SPR). In its crudest forms, self-pierce fastening has been around for hundreds of years;
compare it to the traditional hammer and nails. The system has developed over the past few decades and this versatile and efficient fastening process is certainly one to watch in the future. The SPR technology originated in Australia and was
invented at a Brisbane University in the mid-1970s. Keith Jones, who is the owner of fastener supplier Henrob, was out in Australia on a business trip and came across the technology. Jones saw the technology as a real business opportunity so purchased the intellectual property and brought it back to Europe for further development. As a leader in this field, Henrob is committed to pushing
the boundaries of SPR technology. According to Henrob’s Phil Halsall, there is an important
difference in service life between a pre-drilled and riveted joint and one that is joined using SPR. The fatigue life of the SPR exhibits a tenfold improvement over the blind fastener and this is why SPR has been so readily adopted on many body- in-white vehicle applications. Thanks to the technology, the company has a full order
book and can plan with confidence. The market place has changed over the last three years and there has been complete swing in the way aluminium and high strength steel has been adopted in the automotive market place on a global basis and at every OEM. Henrob is determined to keep one step ahead of its competition and continue its rapid expansion. Halsall believes that the company needs to manage this growth and deliver a level of profitability that will allow future investment in the technology development and high production volumes.
Self-clinching option
As materials are formulated to be lighter, panels are made from harder material to maintain their strength. Harder materials are harder to join and as well as being less suitable for welding, they are tougher to pierce. A fastener using a pre- drilled or punched hole overcomes the problem. The PEM nut is an internally threaded fastener, that
when pressed into ductile metal, displaces the host material around the mounting hole, causing it to cold flow into a specially designed annular recess in the shank of the fastener. A serrated clinching ring prevents the fastener from rotating in the host material once it has been properly inserted. Thus the nut becomes a permanent part of the host material offering
Fig. 2. The five stage self-pierce riveting process described. 30
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