Gear meshing refers to how the teeth of two gears fit together so that they can rotate with each other. This process is called meshing. It is essential for the normal operation of mechanical transmission parts, transmissions, engines and other parts of machinery.
1. Types of gear meshing
Gear meshing is a key component of the operation of many machines and is widely used in various industries. According to different classification methods, the types of gear meshing transmission are as follows.

• According to whether the angular velocity of a pair of gear meshing transmission is constant, it can be divided into non-circular gear meshing transmission and circular gear meshing transmission.
• According to the shape of gear teeth, it can be divided into involute gear meshing transmission, circular arc gear meshing transmission, cycloid gear meshing transmission, etc.
• According to the shape of gear teeth, it can be divided into spur gear meshing transmission, helical gear meshing transmission and curved gear meshing transmission.
• According to the hardness of tooth surface, it can be divided into soft tooth surface gear meshing transmission and hard tooth surface gear meshing transmission.
• According to the working conditions of gears, it can be divided into open gear meshing transmission and closed gear meshing transmission. The former has no enclosed gearbox, the gear teeth are exposed, easily affected by dust, and the lubrication condition is poor; the latter has a closed gearbox.

2. Gear meshing conditions
From the meshing principle, for any gear, whether it is an involute gear or a double arc gear, if they are properly meshed, the meshing conditions are met: the normal vector of their contact point is perpendicular to the relative motion speed between them, and then they are correctly meshed.
However, different types of meshing gears have different meshing conditions. According to the classification of meshing gears, the meshing conditions are mainly the following.

• Spur gears: The modules of the two gears must be equal, and the tooth profile angles on the pitch circles of the two gears must also be equal.
• Helical cylindrical gears: The normal modules of the two gears are equal, the tooth profile angles are equal, the helix angles are equal, and the helix directions are opposite.
• Straight bevel gears: The large end modules and tooth profile angles of the two gears are equal respectively.
• The modules of the two gears must be equal, and the tooth profile angles on the pitch circles of the two gears must be equal. The normal modules of the two gears are equal, the tooth profile angles are equal, the helix angles are equal, and the helix directions are opposite. The large end modules and tooth profile angles of the two gears are equal respectively. Due to the standardization of gear processing tools, the gear meshing conditions must be equal to the module and pressure angle. The condition for continuous meshing of gears is that the contact degree must be greater than 1.

3. Factors affecting gear meshing failure
Due to the different application occasions, working conditions, gear materials, heat treatment processes, etc. of gear meshing transmission, its failure modes are varied, but the common failure modes are the following five.

• The gear teeth are broken

The gear under load in the running project is like a cantilever beam. When the root of the pulse cycle stress exceeds the fatigue limit of the gear material, cracks will occur at the root and gradually expand. When the rest of the part cannot withstand the transmission load, it will occur. Broken teeth phenomenon. Gears may also break due to severe impact, eccentric loading and uneven materials during work.

• Gear surface fatigue pitting

When the teeth of two meshing gears are in contact, the action and reaction forces between the tooth surfaces generate contact stress on the two working surfaces. As the position of the meshing point changes, the gears move periodically, so the contact stress changes with the pulsation cycle. Under the long-term action of this alternating contact stress on the tooth surface, fine cracks will appear at the cutter marks on the tooth surface. As time goes by, this crack will gradually expand laterally on the surface. After the crack forms a ring, a small area of ​​​​peeling occurs on the surface of the gear teeth, forming some fatigue shallow pits.

• Gear surface wear

For open gear transmission or closed gear transmission containing unclean lubricating oil, due to the relative sliding between the meshing tooth surfaces, some hard abrasive particles enter the friction surface, thereby changing the tooth shape and increasing the tooth gap. Make the gear too thin and break the teeth. Under normal circumstances, only when there are abrasive particles mixed in the lubricating oil will the abrasive wear of the tooth surface be caused during operation.

• Tooth surface glue

For high-speed and heavy gear transmission, due to the large friction force on the tooth surface, high relative speed, and excessively high temperature in the meshing area. Once the lubrication conditions are poor, the oil film between the tooth surfaces will disappear, causing the metal surfaces of the two teeth to contact directly, resulting in mutual bonding. When the two tooth surfaces continue to move relative to each other, the harder tooth surface will tear off part of the material on the softer tooth surface along the sliding direction, forming grooves.

• Plastic deformation of tooth surface

Under impact load or heavy load, the tooth surface is prone to local plastic deformation, which will cause the curved surface of the involute tooth profile to deform.
Before delivery, Tenfaye will also conduct a gear ring meshing test to further ensure the quality of the large gear ring and provide customers with more satisfactory products. High quality, please choose Tenfaye.