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Installation and Maintenance of Planetary Gearbox

In the gearbox family, planetary gearboxes are widely used in the drive systems of servo, stepping and DC brushless motors (drive motors) because of their small size, high transmission efficiency (85~90%), wide speed reduction range (1:3~100) and high precision (small backlash). On the premise of ensuring precise transmission, it can reduce the rotating speed, increase the torque and reduce the ratio of inertia between load and driving motor. However, there are often failures due to improper installation in actual use. The broken shaft of planetary gearbox and driving motor is one of the main fault types. The analysis of broken shaft mechanism is helpful for customers to know how to install planetary gearbox correctly and give full play to the role of planetary gearbox.


1. Correct Installation of Planetary Gearbox


Correct installation, use and maintenance of planetary gearbox are important to ensure the normal operation of mechanical equipment. Therefore, when installing the planetary gearbox, it must be carefully assembled in strict accordance with the following installation sequence.


Step 1: Before installation, confirm whether the motor and gearbox are in good condition, and strictly check whether the sizes of all parts connected with the drive motor and gearbox match. It refers to the positioning of driving motor flange, the positioning of lug boss and shaft diameter and gearbox flange, the size and fit tolerance between groove and aperture. Wipe the dirt and burrs on the surface.


Step 2: Unscrew the screw plug on the process hole on the side of the gearbox flange, turn the input end of the gearbox to align the socket head cap with the process hole, and insert the socket head cap tool to tighten the socket head cap.


Step 3: Hold the drive motor by hand, make the keyway on its planetary gear shaft perpendicular to the holding screw at the input end hole of the reducer, and insert the drive motor shaft into the input end hole of the gearbox. When inserting, the concentricity must be consistent and the flanges on both sides should be parallel. If the concentricity is inconsistent or the flanges on both sides are not parallel, you should find out the reason. In addition, during installation, it is strictly prohibited to use hammering, which can prevent the axial force or radial force of hammering from damaging both bearings, and can judge whether the two fit properly through the assembly hand feeling. The method to judge the matching concentricity and flange parallelism is that the flanges of the two are basically close to each other and the gaps are consistent after the two are inserted into each other.


Step 4: In order to ensure the uniform receiving force of the flange connection, you should first screw the fastening screw of the driving motor arbitrarily, but do not tighten it. Then gradually tighten the four fastening screws at diagonal positions. Finally, tighten the screw at the input end hole of the gearbox. Be sure to tighten the fastening screw of the driving motor before tightening the screw at the input hole of the gearbox.


Note: The correct installation between gearbox and mechanical equipment is similar to the correct installation between gearbox and driving motor. The key is to ensure the consistency of concentricity between the output shaft of gearbox and the input shaft of the driven part.


2. The Main Failures of Planetary Gearbox in the Long-Term Operation


(1) The bearing chamber of the planetary gear box is worn, including the wear of the housing bearing box, the bearing chamber of the inner hole of the box body and the bearing chamber of the gearbox.

(2) The diameter of the gear shaft of the planetary gear box is worn. The main wear parts are the shaft head, keyway, etc.

(3) The shaft bearing of the transmission shaft in the planetary gearbox is worn.

(4) The joint surface of planetary gearbox is leaking.

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