Planetary Gearboxes

Failure Type

Failure Characteristics

Diagnostic Methods

Gear Tooth Breakage/Cracks

Abnormal vibration, metal debris, abnormal fluctuations in meshing frequency

Vibration spectrum analysis: Monitor changes in meshing frequency and its harmonics; Envelope demodulation analysis: Identify periodic impact components

Bearing Wear/Pitting

Abnormal temperature rise, high-frequency noise, increased radial vibration

Temperature monitoring: Real-time tracking of bearing zone temperature; Envelope demodulation analysis: Extract bearing fault characteristic frequencies

Lubricant Oil Leakage

Oil stains at the gearbox joints, oil level drop, lubrication failure

Visual inspection: Locate leakage points; Pressure testing: Verify the pressure resistance of seals

Planet Carrier Eccentricity

Output torque fluctuations, increased low-frequency vibration

Shaft center trajectory analysis: Evaluate the motion trajectory of the planet carrier; Phase analysis: Compare the phase difference between input and output shafts

Tooth Surface Pitting/Spalling

Continuous noise, vibration energy concentrated at meshing frequency

Sideband analysis: Detect sideband components on both sides of the meshing frequency; Refined spectrum analysis: Improve resolution of low-amplitude fault signals

Repair of broken teeth/cracks in gears

Stop the machine immediately and disassemble the faulty component. Use a three-coordinate measuring instrument to test the shape and position tolerance of the tooth surface.

If the crack depth is ≤ 10% of the tooth width, laser cladding technology can be adopted for repair. If the limit is exceeded, replace the gear set.

When assembling, the side clearance of the gear pair needs to be calibrated to 0.05-0.15mm and coated with anti-micro-pitting lubricant.

Bearing maintenance plan

Replace grease-lubricated bearings regularly (every 5000 hours), and for oil-lubricated bearings, monitor the viscosity index of the oil (ISO VG 320).

When installing, the hydraulic press-fitting method is adopted to control the interference fit. The recommended fit tolerance between the outer ring of the bearing and the seat hole is H7.

Upgrade of the sealing system

For the dynamic sealing part, a double-lip skeleton oil seal (NBR material) is adopted instead, and a labyrinth sealing structure is added.

The static sealing surface is coated with Loctite 587 flat sealant, and after curing, its pressure resistance capacity can reach 25MPa.

Planetary carrier calibration process

The coaxiality of the input shaft and the planet carrier was adjusted using a laser alignment instrument, with the error controlled within 0.02mm.

After assembly, a no-load running-in test was conducted to monitor the effective value of the vibration velocity (≤4.5mm/s).

Tooth surface strengthening treatment

The new gears need to undergo carburizing quenching (HRC58-62) and superfinishing (surface roughness Ra≤0.4μm).

During operation, extreme pressure additives (sulfur-phosphorus type) should be added regularly to enhance the anti-sticking ability of the tooth surface.