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Replacing an assembly of 70 pressed parts and brackets with a single megacasting is proving to be a gamechanger in Tesla’s Model Y.
Always the innovator, Tesla CEO, Elon Musk, claims the idea of a “Megacasting” came to him when one day, considering a die-cast toy car on his desk, he wondered what the practical size limit for casting would be. After some research, he learned that there really is no size limit.
Of course, the idea of using die-cast parts in the construction of motor vehicles is not new, what is new is the scale of the casting. Imagine three castings spanning the entire underbody of the vehicle.
Fortunately for Musk, there was an Italian company in Brescia that was already working on a Giga press. The company, IDRA, had already recognized the potential for lightweight structural megacasting in electric Vehicle applications.
So driven by a vision of a highly automated and low-emissions process to produce large aluminum die-castings, IDRA set about building its first Giga press, the OL 6100, in 2017.
At 60 feet long by 24 feet wide and 18 feet high this die-cast press is as big as a house. Weighing 950,000 lb, it has a rated clamping force of 6,000 metric tons. This allows Tesla to cast a single-piece front or rear underbody for a Model Y, or as a multi-cavity machine, either of these pieces can be produced in two halves.
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Current passenger car bodies are made up of tens or hundreds of individual pressings and brackets, produced from a range of different materials that have to be joined together using welding, fasteners, or adhesives.
Tesla’s plan is to use two huge single castings for the front and rear underbody sections and to connect them with another casting for the battery pack that will also serve as a stressed member of the body structure. This innovation reduces weight and greatly simplifies vehicle assembly.
According to Musk, the megacasting will reduce the number of pressings from 70 parts to 1. Not only will this cut process time, it will also positively impact the capital expenditure and maintenance on the robots required to assemble the parts.
This rationalization of the assembly operation will likely save Tesla a further 20% in energy requirements compared to the current process, with a potential to reduce the length of the assembly line by about 20% as well.
What is more, the cost savings are not only associated with production, inspection, and checking fixture costs are also dramatically reduced. Instead of having to control the process and materials of 70 parts, the integrity of the assembly relies on a highly automated and repeatable single process.
The yield using the 6,000 ton Giga press producing a complete front or rear underbody megacasting is also greater than having to produce the part in two halves in a smaller press. Each part, whether it is the half or the full-size piece, requires an extra 40 pounds of surplus material to fully charge the system.
The single-piece casting also simplifies logistics and sequencing by eliminating a multitude of suppliers and part numbers, possibly in different locations each with its own unique constraints. In Tesla’s case, the Giga press is integrated into the manufacturing process with the possibility to supply the line directly.
As of February 2021, Tesla had three casting machines installed at Giga Shanghai, two machines at the Tesla Factory in California, and one machine partially installed at each of Giga Berlin and Giga Austin, with foundations in preparation for additional Giga Press machines.
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Although the specification of the Giga Press had been advertised in Idra's catalog since 2018, the first installation of a customized OL 6100 CS Giga Press took place in late-2020 for the production of chassis parts for the Tesla Model Y.
Die casting works by forcing molten metal alloy into a reusable mold, also known as a die, then removing the finished piece from the mold after it has solidified. The open mold is cooled to 365 °F and cleaned by robots before fresh molten aluminum is prepared for the next cycle to begin 1 to 2 minutes later.
For the Tesla's Giga Press-based casting operation, ingots and off-cuts of aluminum are melted in a natural gas-powered melting oven at 1,600 °F. The molten metal is then pumped through heated pipes to an enclosed warming oven heated to between 1,400 and 1,600 °F, using 540-hp of electrical power.
To produce the rear megacasting of the Model Y, a 180 lb shot of molten aluminum is injected into the cold chamber of the casting mold with a velocity of 22 mph. With a cycle time of approximately 80 to 90 seconds, 40 to 45 completed castings per hour can be produced, equating to about 1,000 castings per day.
As Tesla rolls out these new manufacturing processes and automated production, Musk’s vision of “the machine that builds the machine” is starting to come to life, making the Tesla Model Y's megacasting a gamechanger.
As an engineer with over 40 years of experience in the automotive industry Peter Els sums himself up in one sentence: "Automotive engineer by profession, gearhead by choice." Working from his home on the East Coast of South Africa, Peter spends most of his time analyzing and writing about cars and the exciting technologies driving the future of mobility. He shares his findings, opinions, and experience in several online publications, including a monthly column on the highly respected Automotive IQ portal, articles on FutureCar, Robotics Business Review, and product reviews on the Car Fix Book. When not writing about cars Peter is an avid motorsport follower. Having raced motorcycles for 10 years he still enjoys track-time - although now, on four wheels rather than two.