How to Install the Planetary Reducer Correctly

- Feb 27, 2019-

In the reducer family, the planetary reducer has a small volume (same as the motor diameter), high transmission efficiency (85 to 90%), wide deceleration range (1:3 to 100), high precision (small backlash), etc. Many advantages, and is widely used in the drive system of servo, stepping, DC brushless and other control motors (hereinafter referred to as drive motors). Under the premise of ensuring precision transmission, the speed can be reduced, the torque can be increased, and the moment of inertia ratio between the load and the drive motor can be reduced. However, in actual use, faults caused by improper installation often occur, and the reducer and the drive motor broken shaft are one of the main fault types. 


The analysis of the broken shaft mechanism is beneficial to our customers to understand how to properly install the planetary reducer and better play the role of the planetary reducer.


First, The Broken Axis Problem Occurs in Inconcentric


Some users have broken the output shaft of the drive motor after the equipment has been running for a while. Why is the output shaft of the drive motor twisted? When we look closely at the cross-section of the output shaft of the drive motor, we will find that the outer ring of the cross-section is brighter, and the darker the cross-section to the axis, the last to the axis is the broken trace (dotted mark). This phenomenon is mostly caused by the difference between the drive motor and the reducer.


When the concentricity between the drive motor and the reducer is guaranteed to be good, the output shaft of the drive motor is only subjected to the rotational force (torque), and the operation will be smooth and without pulsation. At different times, the drive motor output shaft is also subjected to radial forces (bending moments) from the input of the reducer. The effect of this radial force will cause the output shaft of the drive motor to be forced to bend, and the direction of the bend will change as the output shaft rotates. If the error of concentricity is large, the radial force causes the local temperature of the output shaft of the motor to rise, and the metal structure is continuously destroyed, which will eventually cause the output shaft of the drive motor to be broken due to local fatigue. The greater the error of the concentricity of the two, the shorter the time for the output shaft of the drive motor to break. While the output shaft of the drive motor is broken, the input end of the reducer will also withstand the radial force from the output shaft of the drive motor. If this radial force exceeds the maximum radial load that the input end of the reducer can withstand, The result will also cause deformation or even breakage at the input of the reducer or damage to the input support bearing. Therefore, it is important to ensure concentricity during assembly!


From the assembly process analysis, if the drive motor shaft and the reducer input are concentric, the drive motor shaft surface and the reducer input end hole surface will be very consistent, their contact surfaces are closely attached, no radial force and deformation space. If the assembly is not centered, there will be no matching or gap between the contact surfaces, and there will be radial force and space for deformation.


Similarly, the output shaft of the reducer also has a broken or bent phenomenon, which is caused by the same reason as the broken shaft of the drive motor. However, the output of the reducer is the product of the output of the drive motor and the reduction ratio. Compared with the motor, the output is larger, so the output shaft of the reducer is more easily broken. Therefore, when using the reducer, the user should pay more attention to the concentricity of the output assembly.


Second, the Broken Shaft Problem Occured by Too Small Output of the Reducer 


If the drive shaft is not broken, but the output shaft of the reducer is broken, in addition to the reasons for the poor concentricity of the output of the reducer, there are the following possible reasons.


First of all, the wrong selection results in insufficient output of the gear unit. Some users mistakenly believe that as long as the rated output torque of the selected reducer meets the working requirements, it is not. First, the rated output torque of the equipped drive motor is multiplied by the upper speed ratio. The obtained value is in principle smaller than the corresponding rated output torque provided by the reducer product sample. Second, it is also necessary to consider the overload capability of the drive motor and the actual application. Maximum working torque. In theory, the maximum working torque required by the user must be less than 2 times the rated output torque of the reducer. In particular, in some applications, this criterion must be strictly observed. This is not only the protection of the internal gears and shafting of the reducer, but also the interruption of the output shaft of the reducer. If these factors are not taken into account, once the equipment is installed, the output shaft of the reducer is stuck by the load. At this time, the overload capability of the drive motor will continue to increase its output until the output shaft of the reducer is subjected to more force. Its maximum output torque will cause the shaft to break. If the rated output torque of the reducer has a certain margin, then the condition of the broken output shaft will be avoided.


Secondly, during the acceleration and deceleration, if the instantaneous impact torque of the output shaft of the reducer exceeds twice its rated output torque, and the acceleration and deceleration are too frequent, the reducer will eventually be broken. . If this happens, you should carefully calculate the increase in torque margin.


Third, the Correct Installation of the Reducer


Proper installation, use and maintenance of the reducer is an important part of ensuring the normal operation of mechanical equipment. Therefore, when you install the planetary reducer, be sure to carefully assemble it in strict accordance with the installation sequence below.


Step 1: Before installation, confirm that the motor and reducer are intact, and strictly check whether the dimensions of the parts connected to the drive motor and the reducer match. This refers to the size and fit tolerances between the positioning boss and the shaft diameter of the drive motor flange and the positioning groove and the bore of the reducer flange; the dirt and burrs of the mating surface are wiped.


Step 2: Unscrew the screw plug on the process hole on the side of the flange of the reducer, turn the input end of the reducer, align the hexagon socket screw cap with the process hole, and insert the hexagonal tool to loosen the hexagon socket screw. .


Step 3: Hand-held drive motor, so that the keyway on the shaft is perpendicular to the input end hole of the reducer, and the drive motor shaft is inserted into the input end of the reducer. When inserting, it must be ensured that the concentricity of the two is the same and the flanges of the two sides are parallel. As the heart is inconsistent or the two sides of the flange are not parallel, you must find out the cause. In addition, it is strictly forbidden to use hammering during installation, that is, the axial force or the radial force of the hammering can be prevented from damaging the two bearings, and the fitting feeling can be used to judge whether the two are suitable. The method for judging the contracted heart and the flange of the two is as follows: after the two are inserted into each other, the flanges of the two are basically close and the gap is consistent.


Step 4: In order to ensure uniform force on the flange connection, first screw the drive motor fastening screw, but do not tighten it; then gradually tighten the four fastening screws according to the diagonal position; finally tighten the reducer The input hole holds the screw. Be sure to tighten the drive motor fastening screw before tightening the input shaft hole of the reducer to tighten the screw.


Note: The correct installation between the gear unit and the mechanical equipment is similar to the correct installation between the gear unit and the drive motor. The key is to ensure that the output shaft of the reducer is concentric with the input shaft of the driven part.


Fourth, the Conclusion


With the continuous development of control motor applications, planetary reducers will be used more and more in the field of motion control transmission. Guangdong Saini Intelligent hopes that you can ensure the correct installation of the planetary reducer before use, bringing reliable and safe operation to your equipment!


Guangdong Saini Intelligent Equipment Technology Co., Ltd., is now a leading professional manufacturer integrated with production, R & D and marketing on speed reducer product in China.We have production workshop over 10,000 square meters based in Dongguan and Shenzhen with more than 50 engineers and over 300 employees.


The brand G+ is now a leading speed reducer in china market, our product Hollow Rotary Table, Cam Indexer, High Precision Right Angle Gearbox and Motorized Stages ranks top 3 in china market. Now, we are making efforts on expanding the international markets, providing more high quality and high cost performance precision speed reducer to the clients worldwide.


Since its establishment, Saini Intelligent has been committed to providing customers with high quality and high performance products from China and the world. The G+ speed reducer has been trusted by reputable companies and factories in china and the world. The clients includes Huawei, Johnson Electric, Han’s Laser, DJI, Foxconn, United Winners, BYD Auto, etc.


You are warmly welcomed to cooperate with us to realize the win-win cooperation.