Conventional construction of modern vehicles involves the assembly of myriad sections of stamped sheet metal that are joined together by welding, rivets, and epoxy to form the chassis structure of the car’s platform.
New cars like the Tesla Model 3 from the company’s German plant, the Maserati Grecale SUV, and the next generation of Volvo EVs depart from convention by building the cars atop just a few very large, very complex aluminum alloy castings. These bolt together to form the entire chassis, with front, center, and rear sections that replace, in Tesla’s case, 370 discrete parts that would need to be joined together to form the car’s chassis.
“Using a simple casting to replace assemblies is something that is quite common and there are a whole bunch of reasons why that is becoming far more prevalent,” noted American Foundry Society vice president of metalcasting technical services, Brian Began.
Global Industry Analysts, Inc. forecasts in a report on the industry that the global market for all types of die casting will total more than $100 billion by 2026, from $76.4 billion in 2022. “Demand for passenger cars and light commercial vehicles across the globe, more so importantly in developing markets, will especially drive robust demand for use of cast products for a range of automobile parts and components in the coming years,” the report explains. “The market is also expected to benefit immensely from the shift towards aluminum over steel and iron products among automakers.”
Tesla employs a casting press from Italian specialists Idra which that dubs a “gigapress” because of the very large size and high pressure employed, creating what Tesla calls a “megacasting” to form the Model 3’s platform.
Volvo’s press, from the Swiss company Bühler, doesn’t have a catchy name (they have the Carat 840 and 920, which operate at pressures of 84,000 kilonewtons and 92,000 kN, respectively) but the company does employ the term “megacasting” to describe the resulting products from these presses. Volvo has installed two Carat 840 presses in its Torslanda, Sweden plant.
Maserati, on the other hand, uses more traditional casting techniques for the Grecale’s chassis, so that company says these are large-scale castings, but not “megacastings.”
Volvo’s casting press supplier Bühler describes the benefits of using large-scale castings in cars on its web site. “New large die-casting solutions now make it possible for a whole body-in-white section to be created as a single piece, allowing automotive OEMs to simplify production, reduce costs, and create a more sustainable vehicle,” the company explains.
There are manufacturing benefits too, according to Began. “There is better modeling of performance and it really simplifies the supply chain,” he said. “There is just one piece for that whole weld assembly from a single source as opposed to numerous components, fastener nuts, and rivets coming from different places. You may go to a single supplier from dozens. A lot of those parts they may have been getting from overseas.”
“Megacasting is of utmost importance for the entire die-casting industry,” stated Cornel Mendler, Managing Director of Bühler Die Casting. “Megacasting gives the trend towards structural casting another push by extending the range of applications to complete body sections with the use of the new large Carat solutions with up to 92,000 kN locking force."
Bühler's site states:
“Megacastings reduce complexity in production by enabling between 70 to 100 parts to be replaced by a single die-cast part. These single-piece castings will generally be produced close to the automotive assembly line, which allows for better integration and reduced transport. Aluminum castings have the potential to be almost CO2 neutral when using low-CO2 aluminum alloys and biogas for the melting furnaces. The aluminum that goes into overflows can be remelted directly and reused in the die-casting cell, thereby avoiding transport and recycling. Thinking a step further, the usage of lighter aluminum parts can reduce the energy consumption of the cars over their entire lifecycle.”
Volvo explains the process in a video: “The process goes like this -- molten aluminum is forced into a high-pressure mold. It solidifies as it cools and is then dipped in water to speed up the cooling process. After some laser cutting and quality checks, the parts produced using this process will eventually become part of the floor structure in our new electric [model] range.”
“This process significantly reduces the number of parts produced and allows for greater design and production flexibility,” the video continues. “Megacasting also helps our sustainability ambitions, as it reduces our environmental footprint across production, gives greater potential for recycled content, and reduces the weight of our cars, which in turn reduces energy consumption and improved energy efficiency.”
Reaping these benefits has its hurdles, however. “These high-pressure die casts, they need bigger footprints,” Began explained. “Some require a deeper hole. A traditional foundry floor isn’t big enough.”
Began toured Mercury Marine to see its installation of a gigapress and was astounded. “I remember walking into that room and hearing that this was just for one machine,” he recalled. “Something like that would normally house three machines. The building needs things like bigger doors and higher ceilings.”
Bühler acknowledges this issue on its website. “Such large solutions require proper planning, looking at the entire process, from the ingot to the body shop,” it says. “These large cells, with integrated peripherals, require a well thought-through setup. It all starts with site planning and the set-up of a process for part handling within the die-casting cell and afterward. Also, the thermal management and spraying process, clever handling of the return material, and the integration of the right peripheral devices are key.”
“Especially for such large projects, thinking about the entire die-casting cells from the melting furnace to the handling of the final part is essential,” Mendler concluded. Click through the slide show to see the complexity of this process.