What is a sprocket

A sprocket is a wheel with cog-type sprockets designed to engage precisely pitched blocks on a chain link or cable. Sprockets are widely used in chemical, textile machinery, escalators, wood processing, three-dimensional parking garages, agricultural machinery, food processing, instrumentation, petroleum and other industries for mechanical transmission.

Causes of sprocket wear

1) The greater the adhesive wear load, the higher the surface temperature, and the more serious the adhesion phenomenon. For a metal material with a certain hardness, the wear test is carried out under different pressures to obtain the relationship between the wear rate and the pressure. When the pressure reaches more than 1/3 of the material hardness, severe wear will occur. According to the stress distribution diagram, it can be known that the maximum stress contact point is the maximum pressure, and its value is 884.4 MPa. Because the quenching hardness at the chain nest is HRC48~52, the corresponding hardness value is 4800MPa. Therefore, the pressure is far less than 1/3 of the material hardness, so adhesive wear is not the main form of sprocket wear.

(2) Contact fatigue wear

The friction pair of sprocket and chain is under alternating contact stress, and fatigue pitting is easy to form on its friction surface. The index for judging the fatigue strength of metal contact is the contact fatigue limit, that is, the maximum stress at which pitting does not occur under a certain number of stress cycles. The contact fatigue limit of 40Cr after surface quenching treatment is σ0H=HRC17 +200, calculated to be σ0H=1016MPa. According to the stress distribution diagram, the maximum stress value of the sprocket socket is 884.4 MPa. Its value is very close to the allowable contact fatigue limit of the surface of the sprocket, and it is relatively easy to cause pitting failure at the maximum stress. However, due to the poor lubrication conditions of the sprocket and the chain, pitting corrosion has not been formed in time, and wear has already been caused. At this time, the main damage form is wear rather than pitting corrosion. Contact fatigue wear is the main form of sprocket wear, which basically determines the service life of the sprocket.

(3) Abrasive wear

Because the chain is inevitably in contact with coal powder, a little coal powder sticks on it and is brought to the contact point of the sprocket chain socket. The coal powder contains a little sharp and hard sand, which will cause the surface material of the sprocket to fall off during the friction process. This is abrasive wear. Abrasive wear is related to the hardness of the friction material and the hardness of the abrasive. From the diagram of the influence of abrasive hardness on wear, it can be seen that when the hardness of the abrasive is close to that of the friction material, the friction material will wear at a high speed. Because the coal powder is mixed with a little sharp and hard sand, this is also one of the main reasons for accelerating the wear of the sprocket.

Improvement measures proposed for the sprocket

(1) The design material of the original sprocket is 40Cr, the overall quenching and tempering hardness is HB220~250, and the teeth are quenched HRC48~52. This method basically cannot improve the wear resistance of the sprocket wheel because of the limited quenching hardness of the teeth. It is suggested to change the sprocket material to 20CrMnTi, carburized and quenched, the hardness of the chain nest can reach above HRC60, and its wear resistance is more than 2.5 times that of 40Cr material. This can greatly increase the service life of the sprocket, reduce the frequency of repairs, increase productivity and reduce production costs;

(2) The shape of the original sprocket chain socket is directly formed by forging, which has a large dimensional error and rough surface, which also reduces wear resistance. With the wide application of CNC machine tools and the reduction of processing costs, it is recommended to leave a small margin after forging and finish machining by digital milling to improve dimensional accuracy and surface roughness, so as to achieve the purpose of improving wear resistance.

Advantages of sprockets

As a new gear product, the transmission speed of the sprocket is high. In its specific application process, due to the advantage of high speed, the noise generated is very small, which is also conducive to the realization of a good processing environment. In its application, the sprocket not only has a relatively high installation accuracy, but also has an ideal machining accuracy, which saves a lot of trouble for future maintenance work. Moreover, the advantage of the compact structure of the sprocket makes it have a larger transmission ratio, and its own service life is also relatively high.

Maintenance of sprockets

1. The tightness of the sprocket should be appropriate. If it is too tight, it will increase power consumption and the bearing will be easily worn; if it is too loose, the sprocket will easily jump and come off the chain. The tightness of the sprocket is as follows: lift or press down from the middle of the sprocket, which is about 2%-3% of the center distance between the two sprockets.

2. The sprocket should not swing and skew when installed on the shaft. In the same transmission assembly, the end faces of the two sprockets should be in the same plane. When the center distance of the sprockets is less than 0.5 meters, the deviation can be 1 mm; when the center distance of the sprockets is more than 0.5 meters, the deviation can be 2 mm. However, there must be no friction on the tooth side of the sprocket. If the two wheels are offset too much, it is easy to cause off-chain and accelerated wear. Care must be taken to check and adjust the offset when changing sprockets.

3. After the sprocket is severely worn, the new sprocket and the new sprocket should be replaced at the same time to ensure good meshing. You cannot just replace a new sprocket or a new sprocket alone. Otherwise, it will cause poor meshing and accelerate the wear of the new sprocket or the new sprocket. After the tooth surface of the sprocket is worn to a certain extent, it should be turned over and used in time (referring to the sprocket used on the adjustable surface) to prolong the service time.

4. The new sprocket is too long or elongated after use, making it difficult to adjust. You can remove the chain links depending on the situation, but it must be an even number. The chain link should pass through the back of the sprocket, the locking piece should be inserted outside, and the opening of the locking piece should face the opposite direction of rotation.

5. The sprocket should be filled with lubricating oil in time during work. Lubricating oil must enter the fitting gap between the roller and the inner sleeve to improve working conditions and reduce wear.

6. The old sprocket cannot be mixed with some new sprockets, otherwise it is easy to produce impact in the transmission and break the sprocket.

7. When the machine is stored for a long time, the sprocket should be removed and cleaned with kerosene or diesel oil, then coated with engine oil or butter and stored in a dry place.

Link-B2B is a professional supplier listing service platform which will provide high quality and trustworthy supplier list to international buyers. If you are looking for sprocket suppliers, feel free to visit Link-B2B.com and send a request.