Did you know that humanoid robots are gradually stepping out of science fiction and into reality, poised to become a pivotal force in shaping our future lives? Imagine a future where a humanoid robot in your home not only handles household chores with ease but also keeps you company, cares for the elderly and children, and even assists you with complex tasks at work. However, making this a reality hinges crucially on achieving lightweight designs for these robots.

A Showdown of Lightweight Materials

1. Aluminum: The Widely Used "Veteran"

Aluminum has long held a significant position in the realm of lightweight materials, boasting a high adoption rate—particularly in the automotive industry. According to estimates by Aladin, the aluminum content per new energy vehicle reached 218.88 kg in 2024, while the figure for traditional internal combustion engine vehicles is projected to hit approximately 180.04 kg by 2025. Aluminum’s advantages lie in its relatively affordable price and excellent processability; it is suitable for various manufacturing techniques such as stamping and CNC machining, and its surface is easily colored. However, in the robotics sector—where the pursuit of extreme lightweighting is paramount—aluminum appears to fall slightly short.

2. PEEK (Polyether Ether Ketone): The High-Performance "Elite Material"

PEEK is a high-temperature thermoplastic known for properties such as heat resistance, wear resistance, corrosion resistance, and self-lubrication. It is widely used in high-end sectors including electronics, automotive, aerospace, defense, and healthcare. In terms of performance, carbon fiber-reinforced PEEK composites offer high mechanical strength and low density—boasting the lowest density among the four lightweight materials discussed here. However, the cost of PEEK is often prohibitive: the global market leader, Victrex (UK), sells it for over 500,000 RMB per ton, while domestic producer Zhongyan sells it for over 300,000 RMB per ton—prices more than ten times higher than those of metals like magnesium and aluminum. This significantly limits PEEK's large-scale adoption, particularly in the cost-sensitive robotics industry.

3. Carbon Fiber Materials: The "Darling" of Aerospace

Carbon fiber materials have truly shone in the aerospace sector thanks to their high strength and low density. Composites made from carbon fiber are not only lightweight but also possess exceptional strength and rigidity, enabling them to withstand immense compressive and tensile forces. However, the complex manufacturing process and high costs associated with carbon fiber materials have limited their widespread application in the field of robotics.

4. Magnesium Alloys: The Rise of the Best Value-for-Money Option

As a rising star among lightweight materials, magnesium alloys are increasingly coming to the fore. In terms of pricing, magnesium is demonstrating a clear cost advantage over aluminum; while the magnesium-to-aluminum price ratio typically hovers between 1.1 and 1.3, it stood at 0.877 as of January 17, 2025—falling below the standard range and indicating exceptional cost-effectiveness.

Magnesium alloys also excel in performance. With a density of approximately 1.8 g/cm³, they weigh one-third less than aluminum alloys of the same volume; specifically, in passenger vehicle "body-in-white" applications, magnesium alloys offer a 33.4% weight reduction compared to aluminum. Furthermore, magnesium alloys outperform aluminum in vibration damping and heat dissipation. Magnesium is the structural material with the best damping properties, effectively controlling noise and enhancing structural stability—a fact reflected in the steadily increasing adoption rate of magnesium steering wheels over the past decade. Regarding heat dissipation, although the thermal conductivity of AZ91D magnesium alloy (54 W/m·K) is lower than that of A380 aluminum alloy (100 W/m·K), this characteristic actually creates a larger temperature differential between the base and the tip of heat sink fins. This accelerates convective airflow within the heat sink, thereby improving overall heat dissipation efficiency.

Unique Advantages of Magnesium Alloys in Robotic Components

• Lightweight Build, Agile Performance
  Agility is crucial for robots. The low density of magnesium alloys significantly reduces the weight of robotic components, thereby lowering the torque and power requirements for drive systems. Take Tesla’s humanoid robot as an example: the second-generation Optimus Gen 2 saw its total weight drop from 73 kg to 63 kg compared to the first generation. This resulted in a 30% increase in speed and significantly enhanced agility in parts such as the fingers.
• Energy Efficiency and Extended Runtime
  Given current limitations in battery energy density, operational runtime has long been a bottleneck for robot development. Magnesium alloys effectively reduce inertial forces during robot movement and alleviate the load on drive systems; this lowers system energy consumption and extends runtime. On December 20, 2024, Baowu Magnesium and Estun jointly launched the "ER4-550-MI," a new magnesium alloy robot. By replacing aluminum alloy with lighter magnesium alloy, the weight of comparable components was reduced by approximately 33%, and the total machine weight by 11%. The cycle speed increased by 5%, and component response became more agile and efficient. Additionally, total energy loss was reduced by 10%, allowing the robot to operate longer and perform more actions on the same amount of power, thereby avoiding the inconvenience of frequent charging.
• Robustness and Extended Service Life
  From a mechanical perspective, lightweight design reduces component mass, thereby minimizing friction and inertial forces. This reduces friction and wear between parts, extending the service life of humanoid robots. Furthermore, lightweighting alleviates stress on drive systems and structural components, reducing the likelihood of malfunctions and lowering maintenance costs. Magnesium alloys excel in this regard, providing a reliable foundation for the long-term, stable operation of robots.