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【Industry news】Technical Analysis of Precision Reducer Used in Industrial Robots

From:liudriverelease time:2015-07-15

An industrial robot is a general-purpose machine equipped with a memory device and an end effect device that can perform various movements or processes to replace human labor. It is often used in production to replace workers with certain monotonous, frequent and repetitive long-term operations, or in hazardous and harsh environments. It can improve the efficiency of production and the quality of products, and is an effective solution for enterprises to supplement and replace labor.
At present, the development of industrial robots is characterized by high speed, precision, compact body, multiple degrees of freedom and increased rigidity. The key areas also require heavy load or fast response. For example, most of the welding robots produced by automobile vehicles are between 150-300Kg, while the assembly robots in the electronics field need to respond quickly to accessories on the assembly line.
In the field of mechanical transmission, the reducer is an intermediate device between the power source and the actuator. Usually, the high-speed power of the motor, the internal combustion engine and the like are transmitted through the pinion gear on the input shaft to mesh the large gear on the output shaft to achieve the purpose of deceleration. And pass more torque. The currently proven and standardized reducers are: spur gear reducers, turbine reducers, planetary reducers, planetary gear reducers, RV reducers, cycloidal pin reducers and harmonic reducers. Since the 1980s and 1990s, in the development of emerging industries such as aerospace, robotics and medical devices, high-performance precision reducers with simple and compact structure, high transmission power, low noise and stable transmission are needed, among which RV reducer is harmonious. Wave reducers are two important reducers in precision reducers.
RV (Rot-Vector) reducer
The RV reducer was developed on the basis of a cycloidal pinion transmission with a two-stage deceleration and a central disc support structure. Since it was put into the market in 1986, it has been the "master" reducer for robots due to its large transmission ratio, high transmission efficiency, high motion accuracy, low backlash, low vibration, high rigidity and high reliability.
Harmonic reducer
The harmonic reducer consists of three parts: the harmonic generator, the flexibility theory and the rigid wheel. The working principle is that the harmonic generator produces a controllable elastic deformation of the flexible wheel, and the flexible wheel and the rigid wheel mesh to transmit the power. And achieve the purpose of deceleration; according to the wave generator, there are cam type, roller type and eccentric disc type. The harmonic reducer has a large transmission ratio, a small profile, a small number of parts and a high transmission efficiency. The single-machine transmission ratio can reach 50-4000, and the transmission efficiency is as high as 92%-96%.

Planetary reducer
Planets, as the name suggests, are planetary reducers that have three planetary wheels that rotate around a sun gear. The planetary reducer is small in size, light in weight, high in load carrying capacity, long in service life, stable in operation and low in noise. It has the characteristics of power splitting and multi-tooth meshing. It is a versatile industrial product with comparable performance to other military grade planetary reducer products, but it has the price of industrial grade products and is used in a wide range of industrial applications. .
The role of precision reducer in industrial robots
The power source of an industrial robot is generally an AC servo motor. Because it is driven by a pulse signal, the servo motor itself can achieve speed regulation. Why do industrial robots also need a speed reducer? Industrial robots usually perform repetitive actions to complete the same process; in order to ensure that industrial robots can reliably perform process tasks in production and ensure process quality, the positioning accuracy and repeat positioning accuracy of industrial robots are very high. Therefore, to improve and ensure the accuracy of industrial robots requires the use of RV reducers or harmonic reducers. Another role of precision reducers in industrial robots is to deliver more torque. When the load is large, it is not cost-effective to increase the power of the servo motor. The output torque can be increased by the reducer in a suitable speed range. In addition, servo motors are prone to heat and low-frequency vibrations at low frequencies, which is not conducive to ensuring accurate and reliable operation for long-term and periodic industrial robots.
The presence of a precision reducer allows the servo motor to operate at a suitable speed and accurately reduce the speed to the speed required by various parts of the industrial robot, increasing the rigidity of the machine while outputting greater torque. Compared with universal reducers, robotic joint reducers require short drive chains, small size, high power, light weight and easy control. There are two main types of reducers that are widely used on articulated robots: RV reducers and harmonic reducers.
Compared to harmonic reducers, RV reducers have higher stiffness and rotational accuracy. Therefore, in the articulated robot, the RV reducer is generally placed at a heavy load such as the base, the boom, the shoulder, etc.; the harmonic reducer is placed on the arm, wrist or hand; the planetary reducer is generally used. On a Cartesian robot.
Market status of reducer
There are two main types of reducers currently used in the field of robots, one is the RV reducer and the other is the harmonic reducer. In the articulated robot, due to the higher rigidity and rotation accuracy of the RV reducer, the RV reducer is generally placed at a heavy load such as the base, the boom, the shoulder, etc., and the harmonic reducer is placed on the arm. , wrist or hand. For high-precision robot reducers, Japan has an absolute leading edge. At present, 75% of the precision reducers in the global robot industry are monopolized by Japan''s Nabtesco and Harmonic Drive (commonly known as RV reducers and harmonic reducers in the industry), including ABB and FANUC. The reducers of international mainstream robot manufacturers such as KUKA are provided by the above two companies. Among them, Harmonic Drive has a 15% market share in the field of industrial robot joints.

According to industry sources, the purchase price of a precision international reducer for the four international giants is 30,000 yuan to 50,000 yuan, and it is sold to domestic customers with a good relationship of about 70,000 yuan, and the average ordinary customer is about 120,000 yuan. The cost of a precision reducer is more than double that of the international giants, and it can be seen how much the profit difference is between them.
In 2013, the global industrial joint type robot reducer shipments were 730,000 units, an increase of 6% year-on-year. At present, the global precision reducer market is basically monopolized by Nabtesco of Japan and Harmonica Drive of Germany. According to the announcement of Shanghai Electromechanical, Nabtesco of Japan has a sales revenue of approximately 3 billion in 2012 and a global market share of 60%.
It is worth mentioning that Nabtesco Corporation of Japan has made a substantial breakthrough in the RV design from the early 1980s to the 1986 RV reducer research, which took 6-7 years; and Nantong Zhenkang and Hengfeng, the first in China. Thailand also spends 6-8 years; it can be seen that there is no shortcut to technology. In other words, the current development level of domestic RV reducers is still in the late 1980s in Japan.
According to unnamed persons in the industry, ABB, FANUC, Yaskawa, KUKA and other international mainstream robot manufacturers have provided reducers from the above two Japanese companies, and they have very strict cooperation conditions with the two companies. When using these two company products, you can no longer use other products, otherwise the partnership will be lifted.
Nantong Zhenkang''s annual output was more than 200 units last year. The products have been tested by many robot manufacturers, including foreign ABB, KUKA, FANUC and domestic Eft, Eston and other enterprises. Among them, Eft has purchased hundreds of RV reducer products after trial.
The core components have always limited the rapid development of this Chinese robot, so it is crucial to realize the localization of the accelerator at an early date.

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