Analysis of coupling failure

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发布时间：2021-04-16 11:54

　　The selection of a coupling primarily depends on the material; generally, there are three types: hard aluminum alloy, engineering plastics, and steel. Secondly, consider the size of the shaft diameter at both ends of the coupling, as well as the coupling's outer diameter and length. Most importantly, select a coupling with a rated torque that matches the actual operating torque of the motor or lead screw. If the selected coupling has insufficient torque and exceeds its rated range, it is easily prone to breakage. Failure Analysis of Gear Couplings: Failures in Lifting Accessory Couplings: ① Severe gear surface wear. ② Significant axial displacement of the inner gear ring, even to the point of disengagement. ③ Broken teeth. ④ Broken coupling connecting bolts. The main causes of the above failures are as follows: First, insufficient or lack of lubricant in the lifting accessory coupling, or improper use of grease, causing grease calcification, resulting in poor or no lubrication between gear surfaces and severe gear surface wear. This can be avoided by replacing the grease with new, qualified lubricating grease, regularly injecting sufficient grease, and preventing oil leakage. Second, excessive error in the horizontality and coaxiality of the two shafts, exceeding the coupling's compensation range, causing incorrect meshing between the shaft teeth and the inner teeth, resulting in partial contact and additional torque. This additional torque can be decomposed into axial force acting on the inner gear ring. The magnitude of this force is proportional to the deviation; the larger the deviation, the greater the force, leading to axial displacement of the inner gear ring in the lifting accessory coupling. If the displacement is too large, it will be uncontrollable, causing severe gear wear, even broken teeth, and disengagement of the inner and outer teeth, ultimately preventing transmission. This type of failure is difficult to handle and requires production downtime. That is, realignment is needed, either realigning the reducer side or the drum side. First, identify the location with the larger offset error. This requires measuring the offset direction of the coupling, i.e., measuring the horizontality and coaxiality of the main shaft and the horizontality and coaxiality of the reducer main shaft, and then realigning according to quality standards to eliminate the fault. In addition, large errors in the horizontality and concentricity of the two shafts cause binding during coupling rotation. This is similar to the reasons for gear wear in lifting accessory couplings mentioned above. The connecting bolts are subjected to additional bending moments in addition to normal forces, causing them to break. This is the main reason. This often occurs when there is a large height difference in the horizontality of the reducer main shaft. Furthermore, thinner bolt diameters, insufficient strength, or poor bolt material can also cause bolt breakage.

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