The Application Of Magnesium Alloy Materials In Lightweight Robots

1. The development and application status of robots

As the development of robots continues to mature, the application of robots has expanded from the earliest industrial fields to medical and health, life services, space and ocean exploration, military and entertainment, etc. Robotics will not only push the manufacturing industry into a new stage, but will also usher in the rapid development of non-manufacturing automation technology.

At present, the United States, Japan, Europe, South Korea and other industrial powers place breakthroughs in robotics technology and promote the development of the robotics industry in an important strategic position in the development of science and technology in all countries. In "Made in China 2025", China also regards "high-end CNC machine tools and robots" as one of the 10 key development areas, and proposes "focusing on industrial robots, specialties, such as automobiles, machinery, electronics, dangerous goods manufacturing, national defense, military, chemical, and light industries. 

The application needs of robots, as well as service robots such as medical and health, home services, education and entertainment, actively research and develop new products, and promote the standardization and modular development of robots." The "National Medium and Long-term Science and Technology Development Program Outline (2006-2020)" also clearly regards service robots as a strategic high-tech priority for future development, and proposes "focusing on service robot application requirements, research design methods, manufacturing processes, and intelligent control. Common basic technologies such as integration with application systems" [5]. 

At present, the average density of industrial robots used in the world's manufacturing industry is 55 units per 10,000 employees, while the density of industrial robots in China is only 36 units per 10,000 employees. In view of the above background, "machine substitution" has become the general trend. In Guangzhou, the representative of the manufacturing industry in the Pearl River Delta, the government has proposed that by 2020, more than 80% of the manufacturing enterprises in the city should use industrial robots and intelligent equipment.

In addition to being widely used in processes such as stamping, welding, and automated assembly lines in the manufacturing industry, robots can also be used to replace traditional manual tasks such as grinding, complex welding, and polishing. Apple uses two KUKA electronic robots to polish the appearance of the Mac Pro twice to produce a mirror-like surface. 

After the external polishing is completed, the robot will also polish the inside of the Mac Pro shell, as shown in Figure 1. Welding robots have played an extremely important role in high-quality and efficient hull welding production, and are gradually transforming to automation. South Korea has adopted a PDA-based mobile ship welding robot Rail Runner, which can enter the enclosed structure of a double-hull ship that needs to be welded, and work in the harsh welding environment of toxic gas and high temperature, instead of manual automatic welding. 

PTJ is a comprehensive high-tech enterprise that relies on the technical background of the Chinese Academy of Sciences and focuses on intelligent robot parts design optimization, manufacturing, and domestic and foreign sales. The company team was established in 2010 and has long been committed to the processing of high-precision, high-difficulty, and easily deformable metal and plastic parts, and the small and medium-sized production and manufacturing of light alloy and composite materials (such as magnesium-lithium alloy, magnesium-aluminum alloy, carbon fiber, etc.) parts. And robot parts procurement and customization services.

The application of robots in non-manufacturing industries is also becoming more and more diverse. Amazon has equipped more than 15,000 Kiva wheeled robots in its distribution center to realize warehouse automation, as shown in Figure 3. These robots move fast and quietly. After receiving digital instructions wirelessly transmitted by the central computer, they scan the bar code labels on the ground to walk through, slide under the shelves, and then send them to the pickers. The R2D4 underwater robot developed by Japan has a maximum diving depth of 4000m, can collect data autonomously, and can be used for submarine volcanoes, shipwrecks and mineral deposits. 

The CR-01 and CR-02 series of pre-programmed and controlled underwater robots, cooperating with Russia by the Shenyang Institute of Automation, Chinese Academy of Sciences, have a maximum diving depth of 6000m, and have completed the survey of the Pacific Ocean. In terms of space robots, Robonaut, a robot developed by NASA in the United States, will replace astronauts in extravehicular work, and its response speed is faster than that of humans, adapting to unforeseen emergencies.

At present, China has entered an aging society, and the problems of medical care, rehabilitation, and assistance for the disabled caused by the aging population structure have also brought huge economic and resource pressures to the entire society. Surgical robots represented by da Vinci robots represent the highest level of current medical robots, and also show the broad application prospects of medical robots. 

Exoskeleton robots have also shown their advantages in assisting the elderly and the disabled to walk. Application potential. In terms of medical robots, many hospitals such as Southwest Hospital in my country use capsule endoscopy robots instead of traditional gastroscopes for gastrointestinal examinations. The robot is only the size of a capsule. After the patient is taken orally, the doctor can observe the inside of the digestive tract 360° through the display screen, and the examination can be completed in about 15 minutes, which not only makes the patient more comfortable, but the disposable capsule also prevents cross-infection and is more hygienic and safe. . 

In terms of robots for the elderly, the Robot Suit HAL, an exoskeleton robot from Cyberdyne of Japan, can assist patients with walking difficulties to achieve rehabilitation, and is also suitable for assisting the elderly in walking. The robot can help the wearer complete standing, walking, grasping and lifting heavy objects, etc. Action, and the continuous working time can reach 280min.

2. Robot materials and their lightweight trends

At present, various grades of metal materials are the first choice of materials for various robot structural parts, such as cast iron, alloy steel, stainless steel, aluminum alloy, and titanium alloy. The first consideration in the design and use of professional robots represented by traditional industrial robots is that they need to have sufficient strength. Therefore, most of their structural parts are made of various types of cast iron, alloy steel and other materials, and some parts are made of aluminum alloy and composite materials. Wait.

Taking into account the high requirements of the detection and rescue robot for reducing its own weight, fast and stable movement, etc., after replacing the 45# steel with flax fiber natural fiber reinforced thermoplastic resin matrix or thermosetting resin composite material to make the main body of the detection robot, the mass of the main body is reduced to 45 kg, which is 190.5 kg less than the original car body mass, and the weight reduction rate is as high as 80.9%. Home service robots have slightly lower requirements for material strength, but have more requirements for robot weight or portability. Therefore, the basic structure of service robots mostly uses aluminum alloy materials. For example, the arm structure of a service robot for the elderly is made of 7075 aluminum alloy. 

The lightweight design of the arm is realized by optimizing the structure, and its performance requirements are guaranteed. As a representative of handicapped robots, exoskeleton robots have higher requirements for weight reduction and portability. For example, the EKSO (Figure 5) exoskeleton robot uses aluminum and titanium alloy as its mechanical structure, and its total weight is only about 23kg. The PRMI autonomous weight-reducing exoskeleton lower limb robot of the University of Electronic Science and Technology of my country is also made of aluminum alloy.

In short, in order to meet the needs of more lightweight, high-efficiency and convenient operation of robots, lightweight robots are the future development trend. In addition to lightweight structural design, lightweight materials are more important. Compared with the lightweight structure, the lightweight material makes the robot have a greater potential for weight reduction and a broader range of applications.

3.The application advantages of lightweight magnesium materials on robots

The metal materials that the robot can choose mainly include steel, aluminum alloy, magnesium alloy, titanium alloy, etc. As the density of steel materials is as high as 7.8g/cm3, although a small number of moving parts of the robot use titanium alloy materials (4.5g/cm3) or aluminum alloy materials (2.7g/cm3) instead of steel materials, the density of titanium alloys is still relatively high. High and expensive, the density of aluminum alloy is also higher than that of magnesium alloy.

As the lightest metal structural material, magnesium or magnesium alloy has a density of 2/3 that of aluminum, which is less than 1/4 of that of steel. For polycarbonate composites containing 30% glass fiber, the density of magnesium does not exceed Its 10%. In addition, my country’s iron and aluminum resource reserves only account for 18.7% and 2.3% of the world’s proportions, but my country’s magnesium ore resources are the richest in the world, and the application of magnesium materials has unique resource advantages. Therefore, magnesium and magnesium alloy materials have significant advantages in reducing weight, improving robot maneuverability, and endurance due to their light weight and high specific strength. They are one of the most ideal materials for manufacturing robots.

The lightweight of robot materials can greatly improve its maneuverability and increase its work efficiency, highlighting the advantages of robots in reducing motion inertia, improving operating speed and motion accuracy. The third-generation ASIMO (Figure 6) of Japan's Honda Company is made of lightweight alloy, and its shell is made of magnesium alloy. This greatly reduces the robot's self-weight, and its walking speed is increased from 1.6km/h to 2.5. km/h, the maximum running speed reached 3km/h.

Although magnesium alloy materials have been initially applied in robots, one of the important bottlenecks restricting the application of magnesium alloy materials in the field of robot parts is still that the strength and toughness of existing grades of magnesium alloys is lower than that of steel and aluminum alloys. There is still a gap in the performance requirements of robot materials, and it is impossible to completely replace steel, aluminum alloy and other materials. Therefore, the development of high-performance magnesium alloys and their forming and processing technologies for manufacturing robot parts is of great significance for reducing the quality of robot moving parts, improving the accuracy of motion, and achieving energy saving.

In October 2015, Beijing University of Technology launched the "Big Scientific Research Advancement Program-Intelligent Robots" in response to the current research status and development prospects in the field of robotics. In addition to the major common key technologies, key components, complete machine R&D, and integrated applications of intelligent robots, the program focuses on the research. A notable feature is that it highlights the “lightweight materials for robots” represented by magnesium alloy materials. key technology research". 

The "big research advancement plan" relies on the R&D team and R&D platform advantages of the School of Materials Science and Technology of Beijing University of Technology in the field of light magnesium alloy materials for more than ten years, and uses high-performance magnesium such as Mg-Zn-Er, Mg-Gd-Er-Zr, etc. Based on the research results of alloy material design, fine structure control, plastic forming mechanism, etc., aiming at the needs of high value-added medical robots and domestic robots in terms of material lightweighting, and developing new high-strength and high-toughness magnesium alloy materials as the goal to develop high-performance Magnesium alloy parts used in domestic service robots such as medical/housekeeping, etc., focus on the lightweight of such robot arms and other moving parts, and gradually realize the overall weight reduction of home service robots.

In the context of my country's manufacturing industry facing industrial upgrading and aging society transformation, in the next ten or even decades, the demand for traditional industrial robots and new domestic service robots will continue to rise, and the robot market application potential is very significant. The application of lightweight alloy materials represented by magnesium alloys in robots has the advantages of significantly improving the maneuverability of robots, reducing energy consumption, and increasing standby time. It is one of the important directions of robot research and development.

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