Why is there a need for backlash between teeth? Taking planetary gearbox as an example, what is the return clearance?
Gear transmission, gear manufacturers seem to have been committed to improving gear accuracy, using different methods to enhance the precision of each gear and the accuracy of gear meshing:

Use more precise molds, injection molding machines, wear-resistant engineering plastics with higher dimensional stability, and more controlled injection molding processes ......

However, the gear clearance of meshing transmission is too small or there is no clearance, which brings disaster to the movement of the gears.

In fact, in order to achieve smooth and fluent rotational transmission in gear transmission, there needs to be side clearance. Side clearance refers to the clearance between the tooth surfaces of a pair of gears when they mesh. According to the measurement direction, it is classified as follows:

1. Circumferential side clearance

In a gear pair, the length of the pitch arc that one gear can rotate while the other gear is fixed is called the circumferential backlash.

2. Lateral clearance in normal direction:

The shortest distance between the non meshing tooth surfaces of two gears when they come into contact with each other is called the normal backlash.

3. Rotation angle side clearance

The maximum angle that one of the gears can rotate when the gear pair is fixed at the standard center distance.

4. Radial side clearance

The difference between the center distance and the predetermined center distance when the meshing side tooth surface and the non meshing side tooth surface are in contact at the same time is called lateral clearance.

5. Axial side clearance

The difference between the assembly distance and the predetermined assembly distance when the meshing and non meshing tooth surfaces of a bevel gear are in contact simultaneously is called axial backlash.

Factors affecting the backlash of planetary gearbox

According to the definition and calculation of backlash in planetary gearboxes mentioned above, the main influencing factors of backlash in planetary gearboxes are closely related to the influencing factors of backlash in gear pairs, mainly including the following three categories:

a、 The manufacturing errors of gears themselves, including pitch errors, tooth thickness tolerances, radial runout, helix deviation, etc. of each gear component in each planetary gear system;

b、 Manufacturing and installation errors related to gear components, including center distance error, ring gear installation error, sun gear installation error, planetary carrier installation error, planetary carrier pin hole position error, etc;

c、 Other influencing factors include bearing clearance, changes in operating temperature, and torsional deformation of shafts and gear components.