What’s Holding Your Car Together?

(Image courtesy of the author.)

The most recent North American Car Utility and Truck of the Year Awards were a heavy endorsement for aluminum body construction in the 2018 model year. The Lincoln Navigator, featuring an all-aluminium body, was selected as North American Truck of the Year. Meanwhile, the Honda Accord with its aluminum chassis was given the nod for North American Car of the Year. These vehicles represent the auto industry’s response to a growing need for fuel economy.

Aluminum is now finding its way into an increasing number of vehicles around the globe—Ford, Lincoln, Honda, KIA, Lexus and others have all introduced aluminum into their manufacturing processes. It’s not just Body in White (BIW); closures are also migrating to aluminium. Hoods, doors and decklids are all candidates for redesign to help lighten the load.

The shift toward aluminium presents a significant change to traditional manufacturing methods. Automakers originally chose steel to build their cars for a reason: it was strong, workable, easy to join and it didn’t need to fly. Aluminum was not a realistic alternative until the development of a process that could provide strong, reliable joints at a speed that met the requirements of a modern automotive production facility.

(Image courtesy of TWI Ltd.)

Self-piercing riveting (SPR) was the answer. Pioneered by Audi in the 1990s, SPR has become the first choice for manufacturers producing aluminum-intensive vehicles. SPR joins two or more layers of material by driving a rivet through the top sheet into a die held under the bottom sheet, locking them together.

There are several advantages to using this method, including:

Joining dissimilar or difficult-to-weld materials
Joining galvanized or pre-painted material without damage to the coating
No predrilled holes required
High strength, comparable or superior to welding
Visually checkable joint
Tools are long lasting
Low energy requirements
Low material waste
Low processing cost
Short cycle time for joints
The process can be fully automated
Compact gun designs easily carried by robots

The development of the self-piercing riveting process has made aluminum a practical consideration for auto body construction. The speed of a typical joining line employing robotically carried rivet guns is comparable to a traditional welding line without the sparks, fumes or need for cooling water that comes with the latter.

(Image courtesy of RIVTEC.)

As the pressure for increased fuel efficiency and lower emissions continues, more uses for aluminum and other lightweight materials will emerge. For this reason, the self-piercing riveting process will play an important role in the future of automotive manufacturing.

Learn more about SPR here.