Japan has a near monopoly on precision reducers used in industrial robots worldwide. In recent years, although China has also mass-produced RV reducers, few domestic robot companies have chosen to use them. Currently, reducers in the Chinese market are generally dependent on imports.
Japanese Yaskawa robot wields a knife to peel peas.
As traditional manufacturing powerhouses, Germany, Italy, Japan, and other countries lead the industry in terms of gearbox products in terms of materials, design, quality control, precision, power density, reliability, and service life.
In the field of mechanical transmission, a speed reducer is an intermediate device connecting the power source and the actuator. It typically reduces the speed of high-speed power from electric motors, internal combustion engines, etc., by meshing a small gear on the input shaft with a large gear on the output shaft, and transmits a larger torque.
Driven by the development of aerospace, robotics, and medical devices, the demand for high-performance precision reducers with simple and compact structures, high power transmission, low noise, and smooth transmission has increased. Among them, RV reducers and harmonic reducers are two important types of precision reducers.
A precision speed reducer is a power transmission mechanism that uses a gear speed converter to reduce the rotational speed of a motor to the desired rotational speed and obtain a larger torque.
Nabtesco gearbox
Currently, there are only a few manufacturers worldwide capable of producing large-scale, reliable precision reducers. The vast majority of the market share is held by Japanese companies: Nabtesco's RV reducers account for approximately 60%, Harmonica's harmonic reducers for approximately 15%, and Sumitomo Heavy Industries (whose market share was not found). Their dominance is particularly pronounced in the robotics field.
Disassembling the internal structure of a precision reducer
Nabtesco was formed by the merger of two Japanese companies: Teijin Seiki and Nabtesco (which produced Japan's first automatic door in 1956). As manufacturers of motion control systems and components, both companies possessed advanced core technologies in their respective business areas and controlled a significant market share.
As the world's largest manufacturer of precision cycloidal pinwheel reducers, Nabtesco produces high-performance reducers, hollow shaft reducers, as well as single-axis servo actuators and controllers.
The precision equipment it produces has high torque, high rigidity and high resistance to overload impact loads, while also having high precision and very low backlash. It is widely used in industrial automation fields such as satellites, radar antennas, industrial robots, semiconductors and welding technology.
Precision reducers are used in the joints of industrial robots.
Harmonic Drive Systems Inc. (HDSI) of Japan is a leading company in overall motion control. Its Harmonic Drive combined harmonic reducers are characterized by their lightweight, compact size, zero gear backlash, and high torque capacity. They are widely used in various cutting-edge fields such as industrial robots, humanoid robots, semiconductor LCD production equipment, photovoltaic equipment, optical instruments, and precision machine tools.
Internal structure of harmonic reducer
To cover the low reduction ratio range that harmonic reducers cannot achieve, HDSI's product line also includes the Harmonic Planetary, a precision planetary gearbox type harmonic reducer. A unique internal gear ring deformation process allows for tighter meshing of the planetary gears, eliminating backlash and achieving precision-level transmission accuracy.
Harmonic Planetary Gears
Harmonic drive reducers are gear transmission systems that use a wave generator to cause controllable elastic deformation of flexible gears, which then mesh with rigid gears to transmit motion and power.
Sumitomo is a construction machinery manufacturer under the Sumitomo Group, one of the world's top 500 companies with a history of over 400 years. Since Sumitomo developed and manufactured its first hydraulic excavator in 1967, Sumitomo hydraulic excavators have been active all over the world.
Sumitomo gearbox
Sumitomo gearboxes include various models such as large helical gear reducers, planetary gear reducers, worm gear reducers, etc. They feature large reduction ratios, high efficiency, and a pin-tooth meshing system with rolling friction and no relative sliding on the meshing surfaces; single-stage reduction efficiency can reach 94%.
As a pinnacle of precision machinery manufacturing, speed reducers have extremely high technical barriers. RV speed reducers are made entirely of high-precision components and meshing gears, which places extremely high demands on materials science, precision machining equipment, machining accuracy, assembly technology, and high-precision testing technology.
Domestic companies often obtain data through reverse engineering in their R&D, knowing only the "how" but not the "why." Therefore, although some domestic companies have made significant breakthroughs in technology, there are still R&D challenges in maintaining precision, precision lifespan, and product lifespan for domestically produced reducers. These challenges result in poor consistency among domestically produced reducers and low replicability between products.
On the other hand, the equipment for processing and manufacturing gearbox components is very expensive. For example, a Megeller surface grinder costs nearly ten million yuan per unit. Without sufficient production volume, the amortization cost of the equipment is frighteningly high.
Domestically produced precision speed reducers are more expensive than their foreign competitors, yet their performance is inferior, resulting in poor sales and an inability to achieve economies of scale and profitability. Without profitability and large-scale production, there are insufficient resources for technological improvement, research and development, quality control, and further improvements in technology and performance.
Currently, there are two main types of speed reducers used in the field of robotics: RV reducers and harmonic reducers. In articulated robots, RV reducers are generally placed in heavy-load positions such as the base, upper arm, and shoulder due to their higher rigidity and rotational accuracy, while harmonic reducers are placed in the forearm, wrist, or hand.
Japan has an absolute leading advantage in high-precision robot reducers. Currently, 75% of the precision reducers in the global robot industry are monopolized by two Japanese companies, Nabtesco and Harmonic Drive (commonly known in the industry as RV reducers and harmonic reducers). Reducers for major international robot manufacturers, including ABB, FANUC, and KUKA, are all supplied by these two companies.
According to industry insiders, major international robot manufacturers such as ABB, FANUC, Yaskawa, and KUKA all rely on these two Japanese companies for their speed reducers. Furthermore, they have very stringent cooperation conditions with these two companies, stipulating that they cannot use other companies' products while using these two companies' products, otherwise the cooperation will be terminated.
The development of core components has always been a constraint on the rapid development of robots in China. If we want to industrialize the robot industry, break free from the constraints of foreign robot companies, and gain independence in the field of robots, we must accelerate the localization of reducers.
