When the Cybertruck was released at the end of 2019, Tesla said that new production technology was needed to produce the car, and the integrated die-casting machine was one of the key equipment.
In September 2020, Musk announced for the first time that the integrated die-casting technology will be used for the production of Model Y rear underbody plates, and will gradually replace more than 370 structural parts of the entire underbody with 2-3 large die-casting parts, which is a bold approach that opens up a new idea for vehicle manufacturing.
Subsequently, the tonnage of the integrated die-casting machine became larger and larger. In October 2022, itra Group, a die-casting machine supplier, announced that it has completed the construction and testing of the 9,000-ton die-casting machine Giga Press and can be put into use immediately, which will be used as the core tool for the production of the Tesla pickup truck Cybertruck.
From Model Y to Cybertruck, Tesla's integrated die-casting machine process has become the best model for automobile factories to improve scale and efficiency, and Tesla factories have also become the most revolutionary products in the car circle.
What is integrated die casting
Die casting technology is a special casting technology. The traditional automobile manufacturing process mainly includes stamping, welding, painting, final assembly and other four links, integrated die casting directly replaces the stamping and welding two processes, through the original design to assemble a number of independent parts to be redesigned, and the use of ultra-large die casting machine once die-casting, directly obtain complete parts, to achieve the original function.
At present, die-casting aluminum alloy products account for about 54%~70% of automotive aluminum. Musk has described integrated die-casting technology as allowing Tesla to build cars like building blocks.
▲ Summary and proportion of aluminum alloy die castings for automobiles
Integrated die-casting technology is an innovation of traditional automobile manufacturing process, and lightweight is the general trend of the development of the automotive industry under the background of double carbon. The application of integrated die-casting contributes to the realization of light weight, taking the Tesla Model Y as an example, the weight of the rear floor assembly is reduced by 30% after using integrated die-casting.
In addition, compared to the existing production process, integrated die casting improves the cycle time by simplifying the production process, thereby improving production efficiency. The application of integrated die-casting technology can also reduce production, land, labor and other costs. Tesla uses an integrated die-cast rear floor, and the manufacturing cost is reduced by about 40% compared with the original.
Technical barriers of integrated die casting
The key to the integrated die casting process can be summarized in 4 aspects:
❶ Material: Integrated die-casting technology relies on heat-free aluminum alloy materials. The heat treatment of aluminum alloy is divided into homogenization annealing of ingots, recrystallization annealing, solution (quenching) heat treatment, aging, deformation heat treatment, etc., traditional aluminum alloy needs to improve the strength, plasticity, toughness, corrosion resistance, fatigue and other comprehensive properties of aluminum alloy through heat treatment. Integrated die-cast large aluminum alloy parts have high precision requirements, and the heat treatment process is easy to cause dimensional deformation and surface defects of auto parts, so heat-free aluminum alloy materials are the key to large-scale integrated die-casting structural parts.
❷ Equipment: Integrated die-casting has high requirements for the clamping force of the die-casting machine, and the die-casting machine has technical barriers for customized design and development and relatively high capital expenditure.
❸ Process: Since the integrated die-casting technology is in its infancy, it requires rich experience and technical accumulation in the vacuum die-casting process to ensure the yield of mass production.
❹ Mold aspect: Integrated die-casting parts, complex structure, high manufacturing cost, long preparation cycle, for the production of die-casting mold put forward higher requirements.
▲ Guangdong Hongtu self-developed self-made heat-free aluminum alloy materials and obtained invention patent authorization
The integrated die-casting process is actually a vacuum die-casting process with a high-vacuum control system, which requires high-precision sensors to control the vacuum extraction process. The process flow is mold closing, pouring, vacuum opening, cavity vacuum exhaust, injection, mold opening, picking, spraying, mold closing again, etc.
In the die casting process, the vacuum tank, the casting vent valve and the cavity vent valve are controlled by high-precision vacuum sensors and four contact points are triggered by parameter setting: pouring vacuum start, pouring vacuum end, cavity vacuum start and cavity vacuum end. The high-speed filling of die casting can easily lead to the gas in the pressure chamber or cavity can not be completely discharged, the gas rolled into the molten metal will exist in the form of pores in the casting, can not be welded, reduce the mechanical properties, so integrated die casting must be equipped with cavity vacuum system.
The mold needs to use a special mold temperature machine to control the mold temperature, and the mold temperature is generally controlled at 120~180 °C. Die casting process to start the vacuum system in time, punch sealed the gate immediately after the rapid vacuuming, the pressure chamber must meet the vacuum degree requirements before filling, try to extend the vacuum time, vacuum valve as far as possible delay closing, vacuum process is very important for the quality of integrated die-casting parts. This process requires the use of high-vacuum die-casting, which has the strongest sealing in vacuum die-casting, and the air pressure of the die-casting environment needs to reach less than 30mbar, while the traditional vacuum die-casting air pressure only needs to be less than 250mbar.
The upstream of the integrated die-casting industry chain is the die-casting machine, material and mold manufacturers, the midstream is the aluminum alloy die-casting plant, and the downstream is the main engine factory. Large die-casting machines are the basis for integrated die-casting in automobiles. Generally speaking, the clamping force of the die-casting machine required for integrated die-casting is more than 6,000 tons. In September 2022, LK Technology and Guangdong Hongtu released a 12,000-ton ultra-large intelligent die-casting unit, which is the world's largest tonnage die-casting machine so far, which is expected to help vehicle-level integrated die-casting parts.
At present, the large die-casting machine used in Tesla's Shanghai Gigafactory is a 6,000-ton die-casting machine jointly developed by Tesla and a subsidiary of LK Technology. In April 2021, LK Group launched the 9,000-ton giant intelligent die-casting machine in Ningbo, which made great breakthroughs in technology and structure, fully meeting the integrated production process of the automotive field, large and heavy die-casting parts and multiple components, and laying a solid foundation for the sustainable development of domestic and international die-casting equipment, which fully shows that Continental has reached the world's advanced level in the R&D and production of giant die-casting machines.
▲ LK Group's 9,000-ton giant intelligent die-casting machine
In addition to Lijin, Yizumi, Haitian Metal and other die-casting machine manufacturing enterprises have also joined the research and development of super-large die-casting equipment, which has greatly improved the production and manufacturing capacity of China's die-casting equipment and made domestic large-tonnage die-casting equipment have stronger international competitiveness.
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