In 2024, the sales proportion of domestically produced industrial robots exceeded foreign brands for the first time, and the market share of domestic industrial robots continues to rise in 2025. The industrial robot industry mainly applies RV reducers and harmonic reducers. High-end applications such as automotive welding, high-precision assembly, and heavy-duty handling have stringent requirements for the long-term operational stability and positioning accuracy of reducers, generally requiring precision reducers to achieve within 60 arc-seconds (1 arc-minute). Currently, this type of precision reducer still relies heavily on foreign brands in the long term.
The key indicator affecting the accuracy gap of reducers is hidden in an extremely small angular unit—the arc-second.
What is an arc-second? A full circle is 360 degrees, 1 degree equals 60 arc-minutes, and 1 arc-minute equals 60 arc-seconds; 60 arc-seconds mean that the angular deviation of the reducer output end rotating one revolution does not exceed 1/60 of a degree. For precision reducers, a transmission accuracy of 60 arc-seconds (i.e., 1 arc-minute) is the clear watershed between the mid-to-low-end and high-end markets, and also a performance threshold that domestic manufacturers have long found difficult to break through.
According to research, although the accuracy of foreign brand harmonic reducers can reach within 60 arc-seconds, their flexspline is prone to fracture, making it difficult to apply in scenarios such as heavy-load and high-precision handling of industrial robots. Domestic manufacturers are generally concentrated in the mid-to-low-end market competition. Although RV reducers have strong load-bearing capacity, their accuracy is generally around 60 arc-seconds due to structural limitations. Precision planetary reducers from foreign brands, such as the Wittenstein Alpha series and the PSC products from Germany's MeliorMotion, generally achieve an accuracy of within 60 arc-seconds, occupying a certain market share in high-end industrial robots, machine tool rotary tables, and semiconductor precision equipment.
In the future, high-end manufacturing in the industrial robot industry will continue to impose high requirements on the accuracy and accuracy life of precision reducers. The 60 arc-second accuracy threshold is also the core barrier for most domestic reducer manufacturers to break through into the high-end market. It is difficult for domestic manufacturers to break the foreign monopoly solely by relying on traditional structures; innovation in underlying technological routes is required.
01. How to Define a Precision Reducer?
Compared with traditional reducers, precision reducers are upgraded products aimed at higher-precision control scenarios. According to general industry classification standards, the accuracy of precision reducers is usually ≤7 arc-minutes. Backlash is the core factor determining accuracy—backlash causes lost motion deviation between the input and output ends, directly affecting the positioning accuracy and repeatability of the equipment.
*Lost motion: The actual motion deviation between the input shaft and output shaft of the reducer, which determines the accuracy of the reducer in controlling equipment positioning.
According to the meshing method of the main transmission, precision reducers can be divided into four major categories:
Precision cycloid type: Represented by RV reducers and cycloid pinwheel reducers, featuring high load capacity and impact resistance, but with complex structures and high costs;
Harmonic type: Relying on the elastic deformation of the flexspline to transmit power, featuring high accuracy and small volume, but with weak rigidity and unsuitability for heavy-load scenarios;
Precision planetary type: Featuring high transmission efficiency, but traditional structures have a small single-stage reduction ratio and relatively low accuracy;
Precision worm type: Represented by roller cams and worm gears, featuring relatively high accuracy, but with larger volumes and low torque density.
02. Stratified Demands of Industrial Robots
Increasingly Stringent Performance Requirements for Reducers
The application scenarios of industrial robots have long formed clear segmented tracks, and the performance requirements for reducers vary significantly under different loads and different processes. Different types of industrial robots suitable for different industrial production scenarios, or even different joints, have different requirements for the transmission accuracy, torque, and rigidity of precision reducers:
Six-axis robots under 10kg: Volume and accuracy requirements are prioritized. All 6 joints basically adopt harmonic reducers. Harmonic reducers have the advantages of small volume, light weight, wide transmission ratio range, and high accuracy, which can meet the needs of light-load robots to achieve high-precision and high-speed motion control in limited spaces.
10-50kg medium-load six-axis robots: Commonly used in occasions such as handling of automotive parts and processing of metal products. They require a certain load capacity, as well as certain requirements for motion accuracy and stability. Such robots usually combine harmonic reducers and RV reducers. At the end-effector joints of the robot, harmonic reducers are used to ensure operational flexibility and accuracy.
Six-axis robots over 50kg: These robots require greater load-bearing capacity and higher accuracy retention, basically adopting RV reducers. RV reducers have a compact structure and can withstand large radial and axial forces. Their high rigidity and high accuracy characteristics can ensure that heavy-load robots have high stability and accuracy when handling and operating heavy workpieces.
SCARA robots of 20kg and below: Have extremely high requirements for positioning accuracy and repeat positioning accuracy, thus also requiring high transmission accuracy and response speed of the reducer. Harmonic reducers are usually used at the rotating joints, and a planetary reducer or belt is used for the up-and-down movement of the Z-axis.
Parallel (Delta) robots: Often have a relatively large output torque, featuring high speed and high rigidity. Most parallel robots apply planetary gear reducers with a smaller reduction ratio at the base joints to meet the needs of high-speed motion and low inertia of the robots. There are also cases where cycloid or harmonic reducers are used at the base joints. The additional axis at the end generally uses a planetary reducer, but in some high-precision assembly scenarios, to improve the positioning accuracy of the parallel robot, 1 harmonic reducer is also used at the end joint.
It can be seen that in most precision manufacturing scenarios, industrial robots mainly use harmonic reducers and RV reducers. Traditional planetary reducers are rarely used in industrial robots because their accuracy and structural miniaturization are not as good as the former two. Of course, in high-end scenarios, many precision planetary reducers from foreign enterprises are still applied relying on the high-precision advantage of within 60 arc-seconds. However, due to their disadvantages of higher prices and longer delivery times, they are gradually becoming disconnected from the rapidly growing industrial robot market.
However, in market research, we found that a few domestic manufacturers have broken the traditional transmission method of planetary reducers. Through self-backlash elimination technology, they have improved the accuracy, rigidity, and accuracy life of planetary reducers, and applied them in industrial robots and machine tools, greatly enhancing the comprehensive performance of industrial robots and machine tools.
03. Self-Backlash Elimination Technology Breaks the Dual Bottleneck of Accuracy and Life
Traditional reducers have an unavoidable pain point: wear inevitably leads to accuracy degradation. Continuous wear during gear meshing will continuously expand the backlash, leading to increased lost motion and decreased positioning accuracy, ultimately affecting the machining quality and service life of the equipment.
The emergence of self-backlash elimination technology provides an underlying solution to this pain point. Different from traditional passive backlash elimination structures, self-backlash elimination reducers can automatically compensate for backlash during gear wear through built-in adaptive adjustment mechanisms, maintaining stable transmission accuracy over the long term, and extending the accuracy life in principle.
Currently, there are two main routes for mainstream self-backlash elimination technology:
One is the tapered gear self-backlash elimination structure represented by the MeliorMotion PSC series, which achieves automatic wear compensation through tapered planetary gears and spring preloading mechanisms, with accuracy controllable within 60 arc-seconds. Europe and China are currently Melior Motion's most important sales markets globally. However, it is facing challenges in the Chinese market. The price war in the industrial robot industry is becoming increasingly fierce, but Melior Motion's costs remain high, making market expansion difficult.
The other is the modified planet carrier self-backlash elimination technology originally created by domestic manufacturers, with the representative product being the H3K series reducer. The H3K series planetary reducer from Aici Technology adopts an innovative structure of a deformable planet carrier and a self-locking tapered sleeve: when wear or initial machining errors occur on the tooth surface, the elastic system of the planet carrier will actively adjust the position of the planetary gears, keeping the planetary gears and the internal gear ring in a zero-backlash meshing state at all times.
For example, the angular transmission accuracy of Aici Technology's H3K-K series products is all within 50 arc-seconds. The torsional rigidity and main bearing overturning rigidity are both greater than those of robot reducers of the same level, and the efficiency is as high as 90%, far exceeding the accuracy of harmonic reducers and surpassing the rigidity and torque of RV reducers.
Aici Technology Reducer Products and Downstream Applications
In addition to planetary reducers, self-backlash elimination technology has also extended to the harmonic reducer track. The dual-flexspline self-backlash elimination harmonic reducer developed by Aici Technology can stably suppress backlash over the long term through the structural design of the inner and outer flexsplines and the limit ring, with the lost motion being about 1/2 of that of foreign harmonic reducers of the same level. The self-backlash elimination plastic harmonic launched for the lightweight needs of humanoid robots adopts PEEK material injection molding process, with a weight only 1/3 of that of traditional metal harmonics. At the same time, it relies on the backlash elimination structure to compensate for material wear, solving the industry pain point of fast accuracy degradation of plastic gears.
Conclusion
60 arc-seconds have never been just an accuracy value, but also a critical gateway for the independent and controllable development of core components in China's high-end manufacturing.
In the past, domestic reducers mostly chased along the mature technological routes of foreign enterprises, always finding it difficult to break through the ceiling of high-end performance. However, the maturity of original technological routes such as self-backlash elimination provides domestic manufacturers with the possibility of breakthrough through lane-changing. With the continuous iteration of underlying technologies by local enterprises such as Aici Technology, the high-end market landscape of precision reducers is loosening, and the boundary of domestic substitution is gradually extending from mid-to-low-end scenarios to the core links of high-end manufacturing.