Innovations in Body Design
The new Porsche 911 with more Die Cast Aluminum Components
The increased use of die cast aluminum components in the Porsche 911 Cabriolet enables more efficient production. This not only reduces the weight of the component, but also eliminates the need for relevant production steps.
The 911 Cabriolet has a lot to offer: its body features more innovative lightweight components than ever before. The consistently evolved composite design – which now consists of more aluminum, less steel and new composite materials – once again cuts the weight of the bodyshell by around 7 %, without making any compromises in terms of stability, rigidity and safety, which are all at least at the same exemplary level set by the predecessor model.
An increase in the amount of aluminum used lies at the core of the evolved, lightweight design of the new 911 generation – in both the Coupé and the Cabriolet. Apart from the front and rear aprons, the outer skin is now made entirely from this light alloy. The new door design – made exclusively from aluminum sheet – reduces the weight of the bodyshell without negatively impacting stability and quality. The high degree of toolmaking competence at Porsche is also evident in the side wall of the Coupé, which is now made of aluminum to cut the overall weight by approximately 12 kg. This posed the challenge of developing the right tools and processes for the job as, compared with steel sheet, there is a significantly higher risk of tearing when drawing light alloys. A draw depth of around 30 centimetres is achieved during production of the 911 Coupé’s side wall.
In addition to high-strength steels, more extruded aluminum profiles were also used in the bodyshell, such as for the front and rear longitudinal members, inner and outer door sills and floor reinforcements. Their share has been increased from three to 25 percent. Porsche also uses more die cast aluminum parts in the new 911, for instance as part of the front spring strut mount, rear tunnel housing, rear longitudinal members and impact absorber mounts. The benefit of die casting is that even complex, geometrical components can be produced as one single component. Reinforcements or screw connections no longer have to be produced and welded individually. As a result, the component not only becomes lighter, but production steps also become obsolete, making production more efficient.
Up to now, one disadvantage of aluminum die cast parts had been the necessary thermal treatment following die casting. This step is required to lend components the desired material properties that are crucial for crash performance, for example. Thermal treatment therefore represented a separate and thus energy and time-consuming step in the production process. In the new 911, Porsche now utilises the temperatures generated during painting processes to perform final treatment of die cast parts.
Materials and production processes define the ideal connection technology: welding, bonding, clinching, screw connections – no less than ten methods are involved in assembling the body of a new 911. One new feature, for example, is friction welding with countersunk head bolts to link components made of aluminum and steel. In this process, the steel bolt is pressed through the aluminum at such a high speed that friction causes the countersunk head bolts to merge with the steel component, creating a particularly strong connection.
The body of the new 911 consists of a multi-material mix and is thus taking the next big step in intelligent lightweight design, advancing the weight reduction strategy started by the predecessor model. At the same time, the evolved body concept also guarantees higher rigidity. Compared with the predecessor model, the 911 Coupé delivers better torsion and bending values. As a result, the 911 stays unwaveringly on course even when driven with a sporty driving style on sections of road with different surfaces.
This article is based on a press release by Dr. Ing. h.c. F. Porsche AG.
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