In July 2019, Tesla published the patent titled ‘MULTI-BODY Integrated Casting Machine and Automotive Frame-Related Casting Method.’

The patent proposes innovations in frame-type integrated die casting technology, die casting machine design, and related areas.

Tesla announced in September 2020 that the Model Y would feature an integrated die-cast rear floor assembly.

This process reduces the weight of lower body components by 30% and manufacturing costs by 40%.

The process immediately sparked great interest and discussion within the automotive industry.

Extra-large tonnage die-casting machines achieve integrated die-casting.

This process integrates many previously dispersed parts into a single structure.

It involves large-scale aluminum casting, which replaces the traditional method of first stamping and then welding or riveting multiple parts.

As a result, it subverts the traditional “stamping and welding” approach to car body manufacturing.

While simplifying the connection structure of the body, it also shortens the body manufacturing time.

Additionally, it effectively reduces body weight.

This allows the industry to see a new direction in lightweight body design.

New energy vehicles have been developing rapidly under the dual-carbon policy in recent years.

Due to the limitation of battery capacity, achieving better range requires the body to be as lightweight as possible.

The lightweight feature of integrated die-casting technology precisely meets the urgent needs of new energy vehicles.

Therefore, domestic new energy automobile brands have quickly conducted research and developed strategic plans.

They actively promote the further development and application of integrated die-casting in the manufacturing of car bodies.

Led by Tesla’s technology, against the backdrop of industry chain resource integration, the “integrated die-casting boom” swept the industry.

History of Integrated Die Casting Technology

One-piece die casting technology is derived from high-pressure die casting, a specialized casting method.

Its principle is to use high pressure to inject molten metal into a precise mold cavity, cool and solidify under pressure, and then obtain high-precision products.

Compared with the general casting method, the die-casting process shows the following characteristics:

① High production efficiency, product manufacturing speed;

② Can produce thin-walled, lightweight and high strength products, complex shape products, metal assemblies;

③ High dimensional accuracy of the product, small machining allowances, conducive to cost reduction and increase efficiency;

④ Products have excellent surface quality, to meet the higher use requirements;

⑤ Alloy type is aluminum-zinc alloy products;

⑥The process is not suitable for small batch production.

It is more suitable for large-scale industrialized production.

The integral die-casting process flow chart is shown in Figure 1.

Reviewing the history of the die-casting industry, we observe that its growth paralleled the rise of the automobile industry in the 19th century.

Large-scale Application

As early as 1904, the H.H. Franklin Company in the United States took the lead by producing an automobile connecting rod bearing frame using die-casting technology.

This marked an important milestone in the development and application of die-casting technology in the automotive industry.

Its large-scale application in the car mainly has the following stages:

（1）origin stage.

From 1904 to the early 1960s, workers relied on manual operation and primitive equipment to carry out various die-casting processes.

During this period, manufacturers mainly applied die-casting technology to produce small parts, such as automobile engine blocks.

The United States and Europe primarily used this technology in automobile manufacturing.

（2）Development stage.

From the 1960s to the early 1980s, automotive die-casting technology was widely used in the Americas, Europe, and Japan.

During this stage, producers mastered key technologies including casting pressure, mold design, and material properties.

Mastering these technologies enabled producers to improve the die-casting process and increase manufacturing speed.

At the same time, manufacturers gradually expanded the application of die-casting technology from small parts to large-scale casting manufacturing.

（3）Progress stage.

From the mid-1980s to 2000, the automobile industry rapidly developed die-casting technology.

This stage enabled manufacturers to achieve more efficient manufacturing and more accurate casting processes.

At the same time, manufacturers gradually applied die-casting technology to more auto and body parts, including wheels, doors, and other large components.

At this stage, die-casting technology is also gradually popularized in China.

（4）Innovation phase.

Between 2000 and 2019, this stage witnessed the development of advanced computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies.

Through the application of virtual simulation software, it has become possible to achieve more precise and efficient design and manufacturing of automotive parts.

At the same time, the state also made heavy investments to support the development of automotive die-casting technology.

Efforts were made to cultivate more die-casting professionals in the automotive manufacturing field and to promote the wider use of automotive die-casting technology.

Generally, manufacturers used this technology to produce single pieces, such as longitudinal beams, front joints of longitudinal beams, and vibration towers.

Manufacturers generally used a die-casting clamping force of 4,000 tons or less.

（5）Breakthrough phase.

So far in 2019, Tesla has pioneered the concept of one-piece die casting, where dozens of parts are die cast into one or two large components.

For example, the Model Y rear floor is made using the one-piece die-casting process.

It covers the inner rear wheel cover plates on the left and right sides of the car, the rear longitudinal beam, the floor joining plate, and the reinforcement plate in the beam.

Manufacturers have reduced the number of parts from 70 to one.

Manufacturers have reduced the number of weld joints from approximately 700–800 to around 50.

This reduction enables manufacturers to modify traditional manufacturing processes and integrate more advanced one-piece die-casting technology, as shown in Figure 2.

The successful application of Tesla’s integrated die-casting technology in the front cabin and rear floor of the Model Y has driven a change in the industry’s body manufacturing process.

Reasons of innovative breakthroughs

Analyzing the reasons behind its success reveals that it is primarily due to innovative breakthroughs in die-casting materials, processes, equipment, and industry chain integration.

The following aspects reflect these breakthroughs:

（1）Material.

Complex automotive structural parts generally feature thinner walls, larger dimensions, and more intricate structures.

Automakers require high mechanical properties for automobile structural parts to ensure vehicle safety during travel.

Manufacturers generally require structural components related to toughness to have a tensile strength exceeding 180 MPa and ductility above 10%.

Strength-related structural components generally require a tensile strength of over 210MPa and an elongation of over 7%.

Achieving a balance between complex structural component design and mechanical properties requires breakthroughs in both die casting methods and materials.

For this reason, in December 2015, Kooijmans led Tesla to develop a proprietary aluminum alloy for integrated die casting quickly.

This alloy has high yield strength, electrical conductivity, and high resistance to thermal tearing.

The alloy’s yield strength can increase from 90 to 150 MPa.

The new aluminum alloy enables Tesla’s die castings to demonstrate even greater stability, allowing them to proceed directly to the next process.

The new aluminum alloy allows Tesla’s die castings to exhibit greater stability.

This enables the parts to move directly to the next process.

Large parts of the car body can be die cast in one piece without requiring heat treatment after the die casting is complete.

(2)Die-casting method.

In conventional high-pressure casting of aluminum alloys, the minimum thickness of parts is usually over 3mm.

Tesla’s integrated die casting process adopts a unique mold layout.

It consists of a set of fixed molds in the center plus four sets of movable molds around the periphery.

Hydraulic presses force these molds to closely fit the movable molds with the fixed molds at the center, forming an airtight cavity structure.

Subsequently, the system presses molten aluminum alloy into the cavity through the gates of the four moving molds from all directions.

The alloy flows and merges to form large, one-piece die-cast structural components.

These components have different cross-sections and a minimum wall thickness of less than 3 mm.

(3)In terms of equipment and industry chain.

After comprehensive analysis and research, Tesla decided to cooperate with IDRA, a supplier controlled by Lijin Group, a Hong Kong company in China.

The goal was to solve the problem of large-scale die-casting equipment.

It took two years to research and develop the OL6200CS equipment, which measures up to 19.5m × 5.9m × 5.32m.

The dimensions of this large-scale die-casting machine are as big as a badminton court.

The effective dimensions of its platform are 2350mm × 2350mm, allowing it to produce parts of any length, width, and height within 2 meters.

With effective platform dimensions of 2350mm x 2350mm, it is capable of producing parts of any length, width and height up to 2 meters.

This equipment can effectively ensure the stability of mold cavity closing under high pressure, and its maximum clamping force reaches 6218t.

In addition, this equipment can output clamping force continuously, with multi-frequency, stable, and controllable performance.

It also provides real-time monitoring of the mold’s internal pressure, temperature, and other parameters.

At the same time, operators can adjust the die casting machine in real time according to changes in the mold.

As a result, Tesla completed the full car body development process—from personnel and equipment to materials and methods—by combining new material research with IDRA’s equipment technology.

Revolutionary Change

This achievement marked the first industrial application of integrated die-casting for large car body parts.

Integral die-casting technology brings a great impact and revolutionary change to the traditional automobile manufacturing process.

Its significance is mainly reflected in the following aspects:

(1)Take the rear floor as an example.

A steel rear floor of a certain model weighs 71.6 kg, while the integrated die-casting aluminum rear floor of the same size in a new model weighs 56 kg.

This represents a weight reduction of 15.6 kg, or about 21.8%.

According to statistics, for every 10% weight reduction of new energy vehicles, electric vehicles (including plug-in hybrids) can reduce electricity consumption by 6.3% and 9.5% respectively.

In terms of range, according to statistics, a 10% reduction in the weight of a new energy vehicle can increase its range by 14%.

Every breakthrough in lightweighting has greatly promoted the development of new energy vehicles.

(2)Safety performance advantages.

Integrated die-casting technology solves the aluminum alloy welding joint strength problems.

On one hand, it improves structural integrity and strengthens the body.

On the other hand, integrated die-casting technology improves automobile performance indicators due to its lightweight characteristics.

For example, reducing a new energy vehicle’s weight by 10% increases its 0 to 100 km/h acceleration performance by 8%.

In terms of braking distance, a 10% weight reduction shortens the braking distance by 2 to 7 meters.

(3)Efficient platform design.

Nowadays, the domestic automobile industry has fully embraced the era of frame-constructed vehicles.

Examples include the Great Wall Lemon Platform, Geely GPMA Architecture, Chang’an Ark Architecture, and Chuanqi GPMA Architecture.

Through the expansion from “same parts” at the physical level to “same method” in the design process and modularization in the manufacturing process, efficient collaboration is realized at multiple levels during the development of new models.

The development of modularized architecture requires uniform interface boundaries.

It also needs flexible positioning strategies, identical welding levels, and variable combination logic for platform parts.

Integrated die casting facilitates the unification of body module interface boundaries and positioning systems through integration and fewer parts.

It also achieves extreme simplification of the process chain, which meets the needs of modular manufacturing for platform architectures.

Moreover, through similarity design of platform structure and architecture bandwidth design, repetitive design work can be reduced.

This effectively improves the efficiency of platform product development and shortens the development cycle of new cars by 1 to 2 months.

(4)Decrease in manufacturing costs.

Take the Model Y with a one-piece die-cast rear floor as an example.

The number of parts is reduced by 79 compared with that of the Model 3.

Additionally, the number of welded joints is sharply reduced from about 700 to 800 down to 50.

In addition, the one-piece die-cast rear floor assembly is made of a new alloy material.

This material does not require heat treatment and is easily recycled.

As a result, the material utilization rate exceeds 95%.

At the same time, part production time has been reduced from one to two hours in the traditional press-welding process to three to five minutes.

Compared with the traditional process, it directly reduces the cost of processing, logistics, storage and labor in the production process.

Industrial Layout and Technical Challenges of One-Piece Die-Casting Technology

• One-piece die casting technology application status

Under the guidance of integrated die-casting technology, domestic and foreign mainstream automobile manufacturers—especially new energy vehicle companies—have started strategic layouts for integrated die-casting molding.

Some automobile manufacturers have already completed trial production of related products.

The use of integrated die-casting molding processes to manufacture car bodies has become a consensus within the industry.

Tesla, as a domestic leader in large-scale integrated die-casting technology, divides its integrated die-casting process route into three stages.

It is currently in the third stage, moving toward the integration of front and rear body development, as shown in Figure 3.

In terms of industrial layout, Tesla, as a pioneer, is overcoming difficulties in materials, equipment, and costs.

It is also challenging itself with higher-order technologies.

The ultimate goal is to realize integrated die-casting of the entire car body.

Following Tesla, domestic new car-making power groups have also advanced.

As of July 2023, the Azera ES6, Xiaopeng G6, and Krypton 009 models have been mass-produced.

Meanwhile, brands such as Qijie, Ideal, Xiaomi, FAW, Chang’an, Chery, Great Wall, and Volvo have planned their layouts.

Models with one-piece die-cast rear floors are expected to be mass-produced in the first half of 2024.

At present, Guangzhou Automobile Group, SAIC Group, BYD, Dongfeng Motor and others are mainly engaged in technical reserves, pending the layout and application.

• Integration of die-casting technology application difficulties and direction of efforts

Industry-integrated die-casting technology application difficulties and efforts in the following areas:

(1)Material.

The traditional die-casting aluminum alloy materials mentioned above require heat treatment and other processes to improve the internal mechanical properties of the parts.

However, the heating and cooling process can cause deformation errors and surface defects in the parts.

Therefore, there is a need to develop a new type of aluminum alloy material with high strength and toughness, excellent casting process performance, and no requirement for heat treatment.

This material would meet the needs of large-scale die casting production.

In the current industry, the research and application of new heat treatment-free die-casting aluminum alloys primarily focus on the Al-Si series and Al-Mg series.

These materials generally have medium strength and toughness.

The direction of material development is to enhance their strength and/or toughness.

This improvement aims to ensure good fluidity and casting performance.

Cooperation between domestic enterprises and colleges and universities is underway to develop new high-performance alloy materials that do not require heat treatment.

This development promotes the integration of the die-casting process.

As a result, it gradually becomes possible to apply integrated die casting to larger and more complex body structure parts.

(2)Equipment.

The core of the integrated die-casting equipment lies in the die-casting unit, it needs a long time, multi-frequency, stable and controllable output more than 6000t clamping force.

At the same time, real-time monitoring and adjustment of mold internal pressure, temperature, and other parameters are also needed.

These requirements make the equipment demands extremely high.

And with the die casting parts more and more large, more and more complex, the required die casting clamping force is also gradually increased.

In addition, integrated die-casting adopts an ultra-high vacuum die-casting process.

Its die-casting environment requires an ultra-high vacuum below 30 mbar.

This process needs to be matched with a high-capacity vacuum machine.

Body module integrated die casting forming force requirements as shown in figure 4.

Currently, die-casting equipment manufacturers are focusing their efforts on resolving technical issues related to control systems and hardware.

For example, Lijin Group has successfully developed intelligent die-casting islands with clamping forces of 4,000 t, 6,000 t, and 9,000 t.

It has solved key technical challenges in automation, including aluminum alloy melting, refining, and quantitative pouring.

It also features intelligent control of vacuum and temperature, robotic cover spraying, and automatic part pickup.

Additionally, it has realized a series of intelligent functions such as production management information systems and real-time intelligent control throughout the die-casting process.

In 2022, Lijin Group released a 12,000t super-large-scale intelligent die-casting unit.

This advancement brings more possibilities for integrated die-casting and molding of structural parts.

(3)Mold.

Die casting molds operate in a different environment compared to other molds.

The molten metal temperature ranges from 300 to 1000 ℃, with aluminum alloy specifically between 670 and 730 ℃.

The molten metal is injected into the cavity at very high speed within a very short time.

The movement of the injection punch drives this and occurs under high pressure, ranging from 150 to 500 MPa, to form the castings.

Die casting alloys cause significant erosion and impact on the mold.

During the die casting process, the mold must withstand temperature changes and enormous pressure.

This often leads to fatigue failure, making the mold’s life noticeably shorter than that of traditional molds.

Generally, mold life ranges from 8,000 to 100,000 pieces, resulting in a higher cost per part.

Currently, the host factory is collaborating with the mold supplier to enhance mold life.

They focus on mold material, mold structure, temperature control systems, forming technology, surface treatment, and other aspects.

One-Piece Die Casting Application Prospect Forecast

• Progressive popularization

Currently, the integrated body molding technology has become one of the 44 key special projects in the national key research and development plan.

This key special mainly to overcome the four key technologies of integrated die-casting technology:

First, aluminum alloy material properties research, new type of high-strength and tough die casting and no heat treatment;

Second, multi-material integrated body of multi-objective optimization design research;

Third, oversized, thin-walled die casting complex molds and processes;

Fourth, in new energy passenger cars, the application of oversized intelligent die-casting equipment for large-sized car bodies is accelerating.

This equipment integrates die-casting parts and environmental parts connections.

The goal is to realize one-piece structural parts and their die-casting forming process.

With national policy guidance supporting major high-end equipment and the new energy automobile industry, integrated die-casting is gradually benefiting from cost reduction and lightweight effects as its scale grows.

As a result, integrated die-casting will be gradually promoted across the industry.

According to current statistics, by 2024, 13 brands are expected to have mass-production models featuring integrated die-casting rear floors.

• Intelligent, large-scale integration

Through cooperation and promotion between vehicle and equipment enterprises, future integrated die-casting parts are expected to achieve a higher degree of integration and more complex structures.

This may even lead to the emergence of fully integrated die-casting car bodies.

Because of this, will give birth to larger, more intelligent integrated die casting equipment.

Currently, die-casting equipment clamping forces have successfully exceeded 6,000 t, 8,000 t, and 9,000 t.

Tesla is promoting the development of a 12,000t casting machine for the production of integrated car bodies.

On the domestic front, Guangdong Hongtu released a research and development plan for a 12,000t super die-casting unit in 2022.

This effort was in conjunction with relevant parties, including Lijin Group, Hongjin Aluminum, and Cavity Mould.

The industry is making efforts to promote one-piece die-casting equipment to large-scale integration and intelligent development.

• Promote the transformation and upgrading of traditional manufacturing processes

Tesla’s integrated die-casting approach to bodywork has revolutionized traditional manufacturing processes and opened up new ways of thinking about new model development.

Instead of being limited by existing market conditions—such as the maximum tonnage of equipment or the maximum size of parts that can be die-cast—and then proceeding to design and produce the car, the approach is reversed.

It starts with the optimal size and function of the part. From there, the necessary equipment, tooling, and materials to manufacture the part are determined.

New equipment, molds, and materials are then developed together with the supplier.

This kind of disruptive new thinking greatly promotes industrial innovation and creativity.

If we give more thought to this kind of thinking, I believe that the industry’s own demand for cost reduction and efficiency enhancement will drive change.

As a result, the industry will promote the transformation and upgrading of more traditional manufacturing processes.

This includes the exploration and application of new materials and their molding processes, as well as new connectivity methods and innovative bodywork and part topologies.

Conclusion

Integrated die-casting from the perspective of industrial mass production, need to do a lot of preliminary work, not overnight can be completed.

Relevant parties in scientific research and technological progress need to cooperate closely and complement each other.

This includes areas such as product design, materials, die-casting equipment, molds, die-casting technology, and casting production.

Currently, traditional enterprises need to invest more than 1 billion yuan to add or renovate a production line.

Integrated die-casting technology can reduce costs across the entire process, including design, technology, procurement, and manufacturing.

However, compared to current traditional technology, the cost difference for a single piece—such as a floor panel—can exceed 1,000 yuan.

The lightweight and simplified processing chain attributes of integrated die-casting meet the demand for whole-car weight reduction.

This is especially beneficial for new energy vehicles, as it can effectively increase their driving range.

Through the integration and cultivation of industry chain resources, the entire industry chain can achieve vertical collaboration and industrial scale effects.

This will effectively reduce manufacturing costs.

Such integration will mark a significant breakthrough in promoting the adoption of integrated die-casting.