What is Gear Backlash?

Gear backlash refers to the small amount of play or clearance between the teeth of a pair of meshing gears, allowing one gear to move slightly when the other is held stationary. Its essentially the gap between the tooth profiles. The existence of backlash is to prevent interference during gear rotation, ensure smooth meshing, and reduce friction.

The core function of backlash is crucial:
First, it provides space for thermal expansion of the gears, preventing them and the housing from seizing due to expansion at elevated temperatures.
Second, it accommodates a lubricating oil film, ensuring adequate lubrication of the tooth surfaces and reducing wear.
Finally, it compensates for minor manufacturing and assembly errors, ensuring the transmission system operates flexibly without excessive noise and vibration.

However, this clearance must be precisely controlled. Insufficient backlash can cause gears to mesh too tightly, generating high temperatures, noise, and accelerated wear, even leading to seizure.

Excessive backlash, on the other hand, can cause impact, backlash error, and significant noise during gear reversal, affecting transmission accuracy and smoothness.

Therefore, in precision machinery (such as robots and CNC machine tools), backlash control is one of the key indicators for measuring its performance.