FTF – Fundamental Train Frequency – cage defect
Cage defects are characterized by the presence of the cage failure frequency (FTF) and its harmonic peaks in the spectrum. Generally, a defect in the cage is accompanied by defects in the ring tracks, and the FTF usually modulates one of these track failure frequencies, resulting in sum and/or difference frequencies.
E.g. for the SKF 22228 bearing, the frequencies are calculated for 1500 revolutions:
![SKF-bearing-fault-fgrequency](https://vibroguard.cz/wp-content/uploads/2023/05/SKF-bearing-fault-fgrequency.jpg)
So in the spectrum we would see 1x TFT peak at 10.8Hz and multiples of 2x, 3x, …
![Bearing_fault_FTF_Cage](https://vibroguard.cz/wp-content/uploads/2024/04/Bearing_fault_FTF_Cage.png)
A real case of diagnosing a damaged cage:
![poškození-klece-obálka](https://vibroguard.cz/wp-content/uploads/2023/06/poskozeni-klece-obalka.png)
![poškození-klece-čas1](https://vibroguard.cz/wp-content/uploads/2023/06/poskozeni-klece-cas1.png)
![porucha-klec-ložisko](https://vibroguard.cz/wp-content/uploads/2023/06/porucha-klec-lozisko.png)
Examples of cage damage: