The gear shaft of the reducer is broken in use, and I don t know what the reason is

The main reasons are:

1. Whether there is a sudden impact load (sudden increase in load, high-speed start at full load, etc.).

2. Birth defects of the material (coarse crystalline structure of the internal metallographic).

3. The cracks left over by processing expand in the alternating load.

4. The transition interface of the hardness left by the heat treatment of the part is exactly at the position of the maximum shear stress.

5. The raw material is not the design material.

6. The heat treatment is not carried out in accordance with the design specifications.

6. The size of the design journal is not enough.

A gear shaft is a mechanical part that supports a rotating part and rotates with it to transmit motion, torque, or bending moment. It is generally in the shape of a metal rod, and each segment can have different diameters. The parts of the machine that make a rotary motion are mounted on the shaft.

Classify. Depending on the shape of the shaft, shafts can be divided into two categories: crankshafts and straight shafts. According to the bearing situation of the shaft, it can be divided into:

Rotating shafts, which bear both bending moment and torque when working, are the most common shafts in machinery, such as shafts in various reducers. The mandrel is used to support the rotating parts only to bear the bending moment and not transmit torque, some mandrel rotates, such as the axle of railway vehicles, etc., and some mandrel does not rotate, such as the shaft supporting the pulley, etc.

Transmission shafts are mainly used to transmit torque without bearing bending moments, such as long smooth shafts in crane moving mechanisms, driving shafts in automobiles, etc.

In addition to the reasons stated upstairs, there is one more important one:

Will there be a "stress concentration" at the fracture?

Agree with the previous answer, I have been engaged in the reducer industry for 5 years, and specific professionals have conducted on-site investigations.

The cause of reducer bearing fracture is characterized by vibration and noise. When the reducer is opened for inspection, it is often found that the gears meshing with each other in the reducer are broken, the tooth surface is seriously worn, the gap between the gears is too large, and some reducers can not produce oil film between the meshing teeth due to the lack of lubricating oil, and some bearings are damaged, which causes the vibration and noise of the reducer. These situations can be eliminated by simply adding lubricating oil to the reducer, adjusting the gap between gears, and replacing bearings and gears.

However, in some cases, the high-speed shaft of the reducer will also break, so let's take a look at several characteristics of high-speed shaft fracture

1) The fracture surface is neat, and the fracture is perpendicular to the axis of the high-speed axis.

2) The fracture surface appears at the stress concentration of the high-speed shaft, such as the shoulder, thread and near the bearing.

Analysis of the cause of the failure and the sudden failure of the reducer, especially the fracture of the high-speed shaft, will stop the production immediately, and require immediate treatment, analyze, judge and eliminate the cause of the failure, find the real cause, and take corresponding measures to enable the production to recover quickly.

The reasons for this are as follows:

1) The high-speed shaft is defective, and the high-speed shaft itself has quality problems that lead to breakage.

2) The reducer is a weak link in the whole belt design, and the safety factor of the design stress of the high-speed shaft is small. That is to say, in response to the above problems, the high-speed shaft can choose to replace a new high-speed shaft of the reducer, and after replacing the new high-speed shaft, track and observe the problems of loud noise and serious vibration, and report to the manufacturer at the same time. Generally, it can be solved by the following methods:

1) Replace a new high-speed shaft of the reducer.

2) Replace a high-power motor and matching coupling.

3) Strengthen the motor base and add six ribs.

Improper reducer selection.

When purchasing the reducer, due to the wrong judgment of the size of the torque, the torque of the output shaft is too large or too small, which can easily lead to the fracture of the reducer shaft. Some users in the selection, think that as long as the rated output torque of the reducer is selected to meet their own needs, this is the wrong selection, the rated output torque of the motor equipped with the reducer multiplied by the reduction ratio, the value obtained is in principle less than the rated output torque of the similar reducer provided by the product sample itself. At the same time, the overload capacity of the motor and the actual maximum operating torque required should also be considered.

Theoretically, the maximum operating torque required by the user. It must be less than 2 times of the rated output torque of the reducer.

Use a reducer for overload.

Overload operation is also a big killer of the reducer shaft breakage, which is a reason with the mantis blocking car, without this no great power can not be overloaded, the reasonable use of the reducer can not only reduce the occurrence of failure, but also make the life of the reducer longer.

The reducer is not installed properly.

Finally, the correct installation of the deceleration and the position of the instrument is very important, it is taboo to install the reducer in an unstable place, it is easy to break the reducer shaft in the fluctuation, and the maintenance and maintenance of the deceleration during use can also be well avoided.

The quality of the reducer in a reasonable situation will not be used according to the shaft breakage, before the use of the reducer first familiar with the manual or consult the relevant staff for guidance, can bring great convenience in the use of the process.

For mechanical products, there is a phenomenon of stress concentration, especially in places where the shape changes sharply, such as notches, holes, grooves, etc., and for gears, the root of the tooth is just the stress concentration point.

Stress concentration has a great impact on the fatigue life of the gear, and for the gear with long-term heavy load, the tooth root part receives a continuous change of stress impact, which is most likely to produce fatigue cracks, and eventually leads to the fracture of the tooth root. Therefore, from a design point of view, this situation should be avoided and rounded corners should be used at the root of the tooth.

At the same time, factors such as material selection, heat treatment, and actual working conditions should also be considered in the design to avoid gear failure.

Why the fracture of the gear teeth often occurs at the root of the tooth is because the bending stress is greatest at the root of the gear tooth, and there is a round root where the stress is concentrated.

FYI.

There are two main kinds of actual effects of gears, contact failure and bending failure, bending failure is broken, which mainly occurs in the root for two main reasons: 1. The transition fillet of the tooth root is too small, resulting in a large stress concentration at the root of the tooth; 2. In the process of gear processing, the root of the tooth is easy to produce steps and a large amount of digging, which will also lead to tooth breakage.

This is related to the force and the manufacture of the teeth. 1. When stressed, it is a tangential tensile force relative to the tooth. Second, in the processing of gear teeth, the root part of the tooth generally has a knife edge or crack. This area is most vulnerable to damage during prolonged use. For more details, you can see the mechanics of materials.

1. The design of the high-speed shaft of the reducer is not strong enough.

This situation generally occurs at the shaft shoulder, and because there is a transition fillet here, fatigue damage is very easy to occur, such as the fillet is too small, the reducer will break the shaft in a short time. The fracture after the shaft is usually relatively flat. In this case, the reducer should be replaced or the design of the reducer should be modified.

2 High-speed shafts are not concentric.

When the motor shaft and the high-speed shaft of the reducer are not concentricity, the radial load of the input shaft of the reducer will increase, and the bending moment on the shaft will be increased, and the shaft will be broken during long-term operation. During installation and maintenance, the position should be carefully adjusted to ensure that the two axes are concentric. In most cases, the motor shaft will not break the shaft, this is because the material of the motor shaft is generally 45 steel, the motor shaft is relatively coarse, and the stress concentration is better, so the motor shaft usually does not break.

3 Broken shaft in the case of dual motor drive.

Dual-motor drive means that two reducers and two motors are installed on the same drive drum. When the high-speed shaft design or selection margin of the reducer is small, it is easy to break the shaft. In the past, it was easy to use a fluid coupling for the drive of a belt conveyor, because it was difficult to ensure the synchronization of speed and force balance between the two motors when starting and running.

At present, most of the fluid couplings have been used, and the phenomenon of shaft breakage is rare, but it should be noted that the coupling should not be filled with too much oil when using, so as to make it have a torque limiting effect and improve the service life of the coupling.

4.There are too many impurities in the reducer.

There will be a lot of impurities in the reducer, and some impurities will cause the formation of the point stone of the gear if they are granular impurities, but how the particles of impurities are very large will easily cause serious damage to the inside of the reducer, and in serious cases, it will also cause the reducer to break the shaft. The gearbox cleaning machine uses the original oil supply and discharge system of the gearbox and the filtered lubricating oil to clean the gearbox, without changing any hardware facilities of the gearbox and adding any cleaning agent, which ensures the safe operation of the gearbox and prolongs the service life of the gearbox. The occurrence of shaft breakage of the reducer is reduced.

When the diameter of the gear is very small, in order to ensure the strength of the gear and shaft, the gear and the shaft are often made into one, which is called the gear shaft.

If it has been running at full load for many years, it is a fatigue broken tooth; Otherwise, it is a brittle broken tooth.

Looking at the tooth fracture, there is a clear fatigue arc (also known as beach pattern) is the fatigue tooth fracture.

If the fracture shows radial patterns (mostly herringbone patterns), it is a brittle broken tooth.

Fatigue broken teeth, indicating that the reducer gear "has reached the end of life"; Brittle broken teeth indicate that there may be a problem with the heat treatment of the gear, or the broken teeth may be caused by overload.

It should not be related to equipment overhaul and coupling misalignment. Unless the broken tooth is broken, it is extremely unlikely that a foreign object will fall into the reducer during maintenance.