Volkswagen Magazine

THINK AHEAD

can we have a little bit less?

The new Passat is lighter than its predecessor. In order to achieve this, all of the components were put to the test. Even the parcel shelf.

 Text Marc Lüttgemann
Photos Volkswagen AG

The robot arm precisely grips a sheet of metal and guides it to the welding system. A loud whirring noise can be heard; light smoke rises and evaporates immediately when a spot weld is set. The smell of melting metal hangs in the air. Then it is done: an aluminium sheet is welded with two steel sheets. Two metals that don’t belong together have been joined – for hot-formed steel and aluminium cannot actually be welded. However, in the new bodywork production hall at the Volkswagen plant in Emden, 18 engineers have now made the impossible possible by means of what is known as “resistance element welding,” which sees Volkswagen writing a new chapter in the history of lightweight construction.

Light is good. A light car consumes less petrol, emits less carbon dioxide (CO2), and often has better handling characteristics. A further incentive: the European Union wants to see vehicles unburdened from unnecessary weight. It stipulates that, by 2020, all manufacturer’s new cars are on average allowed to emit 95 grams of CO2 or less. Because additional weight results in higher emissions, all auto manufacturers are also trying to make their models lighter.
For instance, by using light metals such as aluminium, magnesium, or titanium as well as plastics such as carbon and polyamide. The problem is that these materials are considerably more expensive than steel. For this reason, developers are exploiting all available options and are also trying to make smaller components lighter. It goes without saying that the weight savings here are lower than for big components – but so are the costs.

Titanium, carbon, aluminium – there are many lightweight materials. But they are expensive.

High-tech in the parcel shelf: a robot inserts steel rivets into the component.

The Passat plant.

50 years of Emden 50 years of Emden The Volkswagen plant in Emden has been in existence since 1964. At the beginning, employees there produced the Beetle and then later the T2, Golf I and the Santana, among others. Volkswagen has been building the Passat in Emden since 1977.
Emden is the fourth biggest Volkswagen plant in Germany after Wolfsburg, Kassel, and Hanover. In 2013, its 9,200 employees produced 208,800 vehicles on an area of 4.1 million square metres. And since the plant was founded 50 years ago, it has made a total of 10.7 million vehicles.

Think Blue.Factory. The “Think Blue.Factory.” programme is also being implemented in Emden. The goal is to reduce environmental impacts by 25 percent by 2018 (compared with 2010, measured by each produced vehicle and component part). This goal is also supported on the plant premises by the energy forest, among others. Its biomass is used as a CO₂-neutral fuel to generate heat.

The fact that lightweight construction is now a factor for the entire car can also be seen with the new Passat. For the new Passat, Volkswagen is using many different methods and materials. Engineers are making increased use of aluminium in the electrics. They have completely redesigned the air conditioning unit to make it lighter. The rear axle now weighs nearly five kilograms less than it used to, and the steering system is more than two kilos down on before. Volkswagen exclusively uses four-cylinder turbocharged engines in the Passat, which saves up to 40 kilograms of weight compared with its predecessor. Overall, the developers have managed to make the Passat up to 85 kilograms lighter.

 

It particularly pays off to save weight in the bodywork, if only because this makes up around 40 percent of the car’s weight. In the Passat, hot-formed steel is mainly used for this component. It not only makes it possible to have thinner walls with the same component strength and thus a lower weight than conventional steel, but is also cheaper than aluminium or carbon. A technical highlight with regards to light construction is the previously mentioned parcel shelf.

But what is happening exactly, and how were the engineers able to weld these materials, which are not supposed to be weldable? Christoffer Meyer, technology planner in joining technology at Volkswagen in Wolfsburg, knows the secret: “The resistance element welding process entailed firmly inserting 51 small steel rivets in the aluminium parcel shelf. During production, this sheet is then welded to the adjacent steel components using conventional resistance spot welding guns and is additionally glued.” The best thing about it is that steel and steel are welded by means of the rivets, which in turn joins the aluminium to the steel components of the bodywork.

what’s lighter, and why.

The new Passat weighs up to 85 kilograms less than its predecessor. From the engine to the electrics to the chassis – our infographic shows where Volkswagen developers were able to save weight.

It has been a long journey from laboratory to mass production. The topic of resistance element welding came up at Volkswagen more than ten years ago. Around 2010 it became clear that the technology could be suitable for mass production. The engineers’ first attempts at vehicle production were made in the centre console of the Tiguan; the next step was a floor panel in the footwell of the Polo R WRC. Due to the success of these test runs, the Executive Board gave the green light for resistance element welding in mass production – beginning with the new Passat.

By means of this new technology, the Passat saves more than a kilogram of weight. Far greater savings are conceivable in the future. The use of resistance element welding is being considered for future vehicle projects. “But for larger volumes,” reveals Meyer. This alone could save several kilograms in the bodywork – and thus continue the success story of lightweight construction at Volkswagen.

Far greater savings are conceivable in the future.