At 7:04.957, the Xiaomi SU7 Ultra mass-produced version made its debut in New York City, becoming the fastest mass-produced electric vehicle in New York City's history! From prototype cars to production versions, the application of carbon fiber is not only about material selection, but also a systematic engineering that integrates material science, process aesthetics, and safety verification.
This seemingly simple "black gold" carbon fiber material has undergone a complete transformation from fiber filaments to high-performance vehicle exterior parts in Xiaomi's technology system, with each process engraved with Xiaomi's exploration of performance boundaries.
01 Exploring "Black Gold": The Selection Method of Carbon Fiber
In the era of pursuing ultimate performance and lightweight, carbon fiber has become an indispensable key material in many high-end fields due to its outstanding characteristics, and is known as the "black gold". A seemingly ordinary carbon fiber front hatch requires nearly 11 complex processes from raw materials to finished products before leaving the factory. The path of its formation can be summarized as three key elements: carefully selected materials, complex processes, and rigorous strength verification.
▍Precision research and manufacturing, building a solid foundation of quality
The complexity of the carbon fiber market is beyond imagination, and the primary challenge is the difficulty in distinguishing between genuine and fake. The common carbon fiber stickers and water transfer carbon fiber products on the market may appear fake on the surface, but they are fundamentally different from real carbon fiber. True carbon fiber is the darling of the aerospace industry, favored by high-end equipment such as airplanes and rockets. And it is precisely because of its excellent durability, wear resistance, and corrosion resistance, as well as its ability to maintain stable performance even in extreme environments, that it has become the core reason why we choose carbon fiber.
So in practical applications, how to accurately select materials and clarify processes is particularly crucial. In the selection of carbon fiber products, full carbon and non full carbon are key indicators. Some so-called carbon fiber products on the market are actually "carbon cloth patches", with only one layer of carbon fiber on the surface and filled with materials such as resin and fiberglass inside, not all carbon structures. This type of "carbon cloth patch" product, although marketed as carbon fiber, has a significant gap in performance compared to all carbon products, making it difficult to meet the high performance requirements of application scenarios.
The curing process of carbon fiber also requires great attention, mainly divided into two types: dry carbon and wet carbon. The wet carbon process is relatively simple, but it has many drawbacks, such as difficult control of resin content, use of unsaturated resin, strong odor and non-compliance with production standards, resulting in high product weight, low strength, and easy damage. The dry carbon process adopts pre impregnation technology, which precisely controls the resin content in advance, and then solidifies under high pressure and high temperature to make the product lighter and stronger. Different curing processes can directly affect the final performance and quality of carbon fiber products, so extra caution is needed when choosing.
The "fineness" of carbon fiber is divided by the number of single fibers, and common specifications include 3K, 6K, and 12K. A strand of 3K carbon fiber contains 3000 single filaments, resembling an "embroidery grade" craftsmanship, characterized by delicacy, lightness, high strength, and toughness. On the other hand, 12K carbon fiber contains 12000 single fibers per strand, which is relatively thick and has a rough texture due to the large number of single fibers. It is usually suitable for making large components.
Due to the difference in the number of monofilaments, carbon fiber has significant differences in appearance, performance, and applicable scenarios, so it needs to be carefully considered when selecting materials. Meanwhile, the choice of brand is also crucial. We have chosen the industry-leading Dongli carbon fiber, which is also adopted by luxury brands such as Ferrari. On the carbon fiber front cabin cover of Xiaomi SU7 Ultra, both the outer and inner panels are covered with 3 layers of carbon fiber, with an outer surface area of 1.73 square meters, bringing a more advanced texture effect and more precise structural layout.
▍Carbon fiber assistance opens up a new chapter in performance
In the automotive field, the application of carbon fiber has played a huge value. The Xiaomi SU7 Ultra mass-produced car, prototype car and other models extensively use carbon fiber materials on some parts of the vehicle's interior and exterior decoration.
This high carbon content design has brought significant improvements to the vehicle in various aspects. It reduces the weight of the vehicle, making it more flexible during driving and greatly enhancing its handling; At the same time, it reduces energy consumption; In addition, it also enhances the strength and rigidity of the vehicle body, providing solid and powerful support for the vehicle to achieve excellent results on the track. In the research and development process, we always adhere to the attitude of striving for excellence, strictly controlling every detail of carbon fiber materials, and striving to achieve perfection in every aspect.
This is the material of carbon fiber, from the identification of authenticity, selection of dry and wet processes, to the consideration of full carbon and non full carbon, to the precise differentiation of the number of single fibers included, and finally to the strict screening of brands. Behind a carbon board, there is a comprehensive and authentic selection of materials. It is this persistent pursuit of every detail that has forged the excellent quality of our products.
02 Craftsmanship: Exquisite craftsmanship, forging extraordinary quality
The application of carbon fiber materials is only the starting point for the manufacturing of lightweight components. To convert the basic material into a carbon fiber front hatch cover, a series of precise and rigorous manufacturing processes are required.
Carbon fiber initially existed in the form of threads, and to transform it into a practical carbon fiber front hatch cover, it is first necessary to weave each carbon fiber into a carbon cloth. Subsequently, immerse the carbon cloth in the resin and freeze it at a low temperature of -18 degrees Celsius to ensure the stability of the resin. After thawing, take it out and cut it according to the design requirements. At this point, the carbon cloth has preliminarily solidified, like a piece of "fabric" ready for use, preparing for the subsequent molding process.
This process may seem simple, but in reality, it requires extremely high precision in craftsmanship and environmental control, and subtle differences in each step may affect the quality of the final product.
After the fabric is ready, it needs to be laid onto the mold. This stage has reached the extreme requirements for both molds and labor.
Taking the carbon fiber front hood of Xiaomi SU7 Ultra as an example, the inner and outer panels require two specially customized molds, all of which are made of high-strength P20 steel. P20 steel not only has high hardness and wear resistance, but more importantly, it can withstand the high temperature and high pressure environment inside the hot press tank. After the carbon cloth is laid, the entire mold needs to be sent to a hot press tank for molding. If the mold undergoes even the smallest deformation under high temperature and pressure, it will cause the carbon fiber front compartment cover to be directly scrapped.
For the Xiaomi SU7 Ultra model, over 100 sets of molds have been developed, each equipped with two skilled workers for manual laying. The entire process takes about six hours and must be completed in a clean space. Even more stringent is that carbon fiber needs to be accurately laid layer by layer, perfectly fitting at every corner, and even the texture of carbon fiber must be strictly aligned. Once the paving deviation exceeds 0.5 millimeters, it will have a serious impact on the appearance quality and may even lead to product scrap. Such exquisite craftsmanship requirements make it possible for a mold to only be laid twice a day, truly embodying the spirit of craftsmanship in slow work and meticulous craftsmanship.
After the tiling is completed, the carbon fiber front hatch needs to undergo further curing treatment, which cannot be separated from the hot press tank process. Unlike the room temperature curing method, the hot press can process used by Xiaomi cars tightly connects layers of carbon fibers through heating and pressure. In the hot press tank, the temperature needs to reach 145 degrees and the pressure needs to be 0.7 megapascals. The carbon fiber needs to withstand 6 hours of testing under these conditions. Based on this, the dimensional stability and appearance performance of the carbon fiber front hatch can reach the ideal state. Carbon fiber cured in a hot press can not only withstand more complex working conditions, but also has significant advantages of light weight and high strength.
After the product is removed from the hot press tank, it needs to undergo CNC machining (numerical control machining) to remove any burrs that may exist around it, and to machine the required hole positions for subsequent production. Continuing with sandblasting and polishing, each step aims to achieve the smoothest and most perfect surface of the product. In addition, due to the fact that the carbon fiber front hood is divided into an inner panel and an outer panel, high-precision bonding technology is required for the connection between the two. We use robots for bonding operations to ensure a tight bond between the inner and outer panels.
When all the above processes are completed, only a "blank" has been made, and key coating processes still need to be carried out. The painting of just one carbon fiber front hatch cover takes 3 days. Spray painting is divided into two options: transparent varnish and colored paint. Regardless of which paint is chosen, the requirements for the process are extremely complex.
Firstly, the adhesion of the paint should be considered. Due to the special nature of carbon fiber materials, carbon fiber specific paint needs to be specially adjusted for specific products. Xiaomi has specially adjusted carbon fiber specific paint for the SU7 Ultra model to ensure that the paint can firmly adhere to the surface of carbon fiber.
Secondly, it is necessary to ensure the uniformity of spraying. The surface of carbon fiber is different from metal and plastic parts, and it is difficult to spray. The Xiaomi SU7 Ultra adopts a color separation spraying method. For example, in the coating of colors such as space silver and lightning yellow, the carbon texture in the middle and the colored parts on both sides are sprayed separately. Even when zoomed in, there will be no jagged edges at the joints, achieving a completely uniform coating without any color difference.
Thirdly, after the painting is completed, the durability of the paint surface needs to be inspected. The adhesion, durability, and quality standards of the Xiaomi SU7 Ultra carbon fiber front hood paint surface are the same as those of sheet metal parts, which can effectively avoid problems such as weak paint surface in the aftermarket and being washed away by high-pressure water guns during car washing.
Although multiple rounds of testing have been conducted in each previous process, a comprehensive external inspection is still required before the product leaves the factory. Only by passing this strict inspection can the product truly be labeled as qualified before leaving the factory.
During the inspection process, even some defective products that appear almost perfect at first glance can be found to have potential flaws after careful examination. Even a tiny particle can be judged as unqualified. When the subsequent products enter the loading step, they also need to undergo two rounds of quality inspection. In Xiaomi's standards for carbon fiber, we always adhere to the principle of selecting the best from the best, and our requirements for quality are so strict that they are almost picky.
From carbon fiber materials to the birth of carbon fiber front hatch covers, a total of 11 process flows are required, including weaving, pre soaking, freezing, cutting, laying, hot press curing, cutting, sandblasting, bonding, coating, and external inspection. The standard production cycle is about 7 days. It is precisely these rigorous processes that have created the excellent quality of the carbon fiber front hatch cover.
03 Strict verification: forging a secure "shield"
From materials to craftsmanship, carbon fiber front hatch covers have undergone many tests, but the key to determining whether they can be put into use and ensure driving safety lies in the comprehensive and rigorous verification process.
▍Ultra high speed verification: Challenge the limits and ensure stable performance
As a high-performance car, the Xiaomi SU7 Ultra has 1548 horsepower and a speed of over 350 km/h, comparable to high-speed rail speed. In order to ensure that the carbon fiber front hatch can remain stable and durable under such extreme working conditions, it is necessary to conduct high-speed verification.
In order to conduct this test, the vehicle needs to be pulled to a professional testing site that has the testing conditions for the vehicle to reach a speed of 350 km/h. During the testing process, the vehicle needs to continuously drive at high speeds, and even perform high-speed cornering and other operations. At this point, the carbon fiber components of the vehicle body, including the carbon fiber front hood, must remain non bent and non deformed.
The cost of this ultra high speed verification is extremely high, with only a few experimental sites in the country able to meet the conditions, and the daily venue fee for booking a site can reach hundreds of thousands. However, it is precisely this cost saving investment that ensures the safety of vehicles when driving at high speeds. If the carbon fiber front hood has not been verified for ultra high speed, it may suddenly open during high-speed driving, posing a great safety hazard to the driver and passengers.
▍Pedestrian safety testing: Putting people first, safeguarding life safety
As a daily means of transportation, the pedestrian safety performance of vehicles is crucial. The Xiaomi SU7 and SU7 Ultra come standard with a pedestrian protection system, which can play an important role in low-speed collisions.
When a low-speed pedestrian collision occurs, the vehicle can quickly activate the pedestrian protection device, and the overall front hood is quickly raised. In this way, in the event of a pedestrian collision, if the pedestrian's head hits the raised front hatch, it can provide sufficient buffering distance, reduce the impact force, and minimize the harm suffered by pedestrians, thereby effectively protecting their safety.
During the testing process, we will simulate real collision scenarios. During a collision, the pedestrian protection device will instantly bounce up with a large force, and the carbon fiber front hatch needs to withstand a huge impact force. Xiaomi Auto has conducted extensive testing and optimization to ensure that the pedestrian protection system can function effectively at critical moments, truly safeguarding the safety of pedestrians.
In order to ensure the reliability of the carbon fiber front hood during long-term use, Xiaomi has also conducted a series of comprehensive durability tests.
On the Xiaomi SU7 Ultra model, a light durability test lasting up to 2000 hours was conducted to ensure that the product would not turn yellow, peel or crack under prolonged exposure to sunlight. At the same time, 16 paint tests were conducted to verify the paint's resistance to damage in daily use scenarios such as small stone impacts, ensuring that the paint is not easily peeled off. Even specialized mechanical tests were conducted on the adhesive used for bonding.
Only through repeated verification tests can the quality of the carbon fiber front hatch be truly ensured, making it a "shield" that ensures driving safety and enhances the driving experience.
Every application of Xiaomi SU7 Ultra mass-produced carbon fiber is an ultimate exploration of performance. When the New York North record of 7 minutes and 04.957 seconds was frozen, and when the 11 process carbon fiber front hatch guarded the journey, Xiaomi's triple breakthrough in materials, processes, and verification proved that carbon fiber is not only the "black gold" on the track, but also the technological sincerity within reach of mass-produced cars.
The Xiaomi SU7 Ultra hood comes from Aosheng Hi-tech
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