Precision reducers for industrial robots worldwide are essentially monopolized by Japan. While RV reducers have been mass-produced in China in recent years, few domestic robot companies have adopted them. Currently, the Chinese market generally relies on imports for reducers.
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▲A Japanese Yaskawa robot slicing peas
As traditional manufacturing powerhouses, reducer products from countries like Germany, Italy, and Japan lead the industry in terms of materials, design, quality control, precision, power density, reliability, and service life.
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In the field of mechanical transmission, reducers are intermediaries connecting the power source and the actuator. They typically reduce the speed of high-speed power from electric motors and internal combustion engines by meshing a small gear on the input shaft with a large gear on the output shaft, thereby transmitting greater torque.
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Driven by the development of aerospace, robotics, and medical devices, there is a growing demand for high-performance precision reducers with simple and compact structures, high power transmission, low noise, and smooth transmission. RV reducers and harmonic reducers are two of the most important types of precision reducers.
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A precision reducer is a power transmission mechanism that uses a gear speed converter to reduce the motor's rotational speed to the desired speed and generate high torque.
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▲Nabtesco Reducer
Currently, there are only a few global manufacturers of precision reducers that can provide large-scale and reliable performance. The vast majority of the market share is held by Japanese companies: Nabtesco's RV reducers account for approximately 60%, Harmonica's harmonic reducers account for approximately 15%, and Sumitomo Heavy Industries (SUMITOMO; the percentage is unknown). Their application in the robotics field is particularly overwhelming.
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▲Disassembly of the Internal Structure of a Precision Reducer
Nabtesco was formed through the merger of two Japanese companies, Teijin Seiki and Nabco (which produced Japan's first automatic door in 1956). As manufacturers of motion control systems and components, both companies possess advanced core technologies in their specific business areas and control a significant market share.
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As the world's largest manufacturer of precision cycloid reducers, Nabtesco produces high-performance reducers, hollow shaft reducers, and single-axis servo actuators and controllers.
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These precision equipment features high torque, high rigidity, and high overload and shock resistance, while also offering high precision and very low backlash. They are widely used in industrial automation applications such as satellites, radar antennas, industrial robots, semiconductors, and welding technology.
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▲Precision reducers for various joints of industrial robots
Harmonic Drive Systems Inc. (HDSI) of Japan is a leading company in integrated motion control. Its Harmonic Drive combination harmonic reducers feature lightweight, compact size, zero gear backlash, and high torque capacity. They are widely used in various cutting-edge applications such as industrial robots, humanoid robots, semiconductor liquid crystal production equipment, photovoltaic equipment, optical instruments, and precision machine tools.
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▲Internal structure of a harmonic reducer
To address low reduction ratios beyond the capabilities of harmonic reducers, HDSI's product line also includes precision planetary gearbox-type harmonic reducers. The unique internal ring gear deformation process allows for tighter meshing of the planetary gears, eliminating backlash and achieving precision transmission error.
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▲ Harmonic Planetary Gears
A harmonic drive reducer is a gear transmission system that uses a wave generator to induce controllable elastic deformation of a flexible gear, which then meshes with a rigid gear to transmit motion and power.
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▲ Harmonic Planetary Gears
Sumitomo, a Japanese construction machinery manufacturer under the Sumitomo Group, one of the Fortune 500 companies, boasts over 400 years of history. Since developing its first hydraulic excavator in 1967 using its own technology, Sumitomo hydraulic excavators are now used extensively around the world.
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▲ Sumitomo Reducer
Sumitomo reducers include a variety of models, such as Sumitomo large helical gearboxes, Sumitomo planetary gear reducers, Sumitomo helical gear reducers, and Sumitomo worm gear reducers. With a large reduction ratio and high efficiency, the pin-tooth meshing system uses sleeve-type rolling friction, eliminating relative slip on the meshing surfaces. The primary reduction efficiency can reach 94%.
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As a pinnacle of precision machinery, reducers possess extremely high technical requirements. RV reducers are composed entirely of high-precision components, with meshing gears. This places extremely high demands on materials science, precision machining equipment, machining accuracy, assembly techniques, and high-precision testing technology.
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Domestic companies often conduct R&D through reverse engineering, acquiring data without understanding the underlying principles. Therefore, while some domestic companies have achieved significant technological breakthroughs, domestic reducers face development challenges in terms of precision retention, precision lifespan, and product lifespan. These challenges result in poor consistency and limited reproducibility between products.
Furthermore, the equipment used to manufacture reducer components is extremely expensive. For example, a Meigler surface grinder costs nearly 10 million RMB per unit. Without sufficient production volume, the amortization cost of this equipment is prohibitively high.
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Domestic precision reducers cost more than their foreign competitors, yet their performance is inferior. Naturally, sales are low, and it's impossible to achieve economies of scale and profitability. Without profitability and volume, there are insufficient resources for technological improvement, research, and development, and there's no way to establish quality control, let alone improve technology and performance.
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Currently, there are two main types of reducers used in robotics: RV reducers and harmonic reducers. In articulated robots, RV reducers offer greater rigidity and rotational accuracy, so they're typically placed in heavy-load locations like the base, upper arms, and shoulders, while harmonic reducers are placed in the forearm, wrist, or hand.
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Japan holds a commanding lead in high-precision robot reducers. Currently, 75% of the global robotics industry's precision reducers are monopolized by Japanese companies Nabtesco and HarmonicDrive (commonly known in the industry as RV reducers and harmonic reducers). These two companies supply reducers to major international robot manufacturers, including ABB, FANUC, and KUKA.
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According to industry insiders, major international robot manufacturers such as ABB, FANUC, Yaskawa, and Kuka all rely on these two Japanese companies for their reducers. These companies also have very strict cooperation conditions: they cannot use products from other companies when using these two companies' products, or else their partnership will be terminated.
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Core components have long been a constraint on the rapid development of China's robotics industry. If we want to achieve industrialization, break free from the constraints of foreign robot companies, and achieve independence in the robotics field, we must accelerate the localization of reducers.
