Gear mesh frequency, which is also called tooth mesh frequency, is the frequency at which gear teeth mate together in a gearbox. There are three important frequencies involved in gearboxes: input speed, gear mesh frequency, and output speed. Gearboxes will always have a strong vibration component at the gear mesh frequency.Gear mesh frequency and output speed can be written as:
Gear mesh frequency = number of teeth x shaft speed
Output speed = input speed x input teeth/output teeth
When a gearbox has two or more teeth mesh stages, the calculation of the forcing frequencies become more challenging because there are multiple shaft speeds and gear mesh frequencies. It is thus more difficult to analyze specific faults.
The most common failures in gearboxes are due to:
Gear misalignment
Over load on tooth
Tooth wear
Gear eccentricity
Damaged teeth
Time domain or waveform is a very powerful tool to diagnose gear faults. There is a pulse (spike) in waveform as each tooth meshes.