1. Traditional listening and appearance preliminary judgment method
When the equipment is running or just shut down, preliminary fault location can be made through the senses:
1. Screwdriver listening method: After stopping the machine, place the screwdriver tip against different parts of the reducer housing and put your ear close to the screwdriver handle to listen. If the upper part of the gear box is loud, the gear needs to be inspected; if the bearing seat is loud, the bearings need to be checked; if the whole vibrates evenly, the installation or resonance needs to be checked.
2. Abnormal sound recognition:
Continuous "buzzing" sound: mostly caused by gear wear, tooth surface gluing or excessive clearance.
Sharp "squeaking" sound or "rustling" sound: It is most likely that the bearing is short of oil and the raceway or rolling element is worn.
Intermittent "clang" banging sound: It may be that the gear teeth are broken or the connecting parts (bolts, key pins) are loose, and the machine needs to be stopped immediately.
"Gurgling" sound: Insufficient lubricating oil or deterioration of oil quality leads to dry friction.
2. Vibration and spectrum analysis positioning method
Use professional instruments such as vibration pens and spectrum analyzers for digital diagnosis:
1. Vibration amplitude and direction monitoring: measure the vibration speed, displacement or acceleration of the reducer bearing seat and input/output shaft. It is necessary to measure the horizontal, vertical and axial directions at the same time. For example, large vibration in the horizontal direction may be a gear meshing problem, and large vibration in the vertical direction may be a bearing problem.
2. Spectrum feature identification:
Gear failure: If the frequency spectrum is dominated by the gear meshing frequency and the amplitude increases, modulation sidebands appear at intervals with the gear shaft rotation frequency (in a "comb-like" structure), and the high-frequency noise component increases, which usually indicates gear wear, pitting, or poor alignment.
Bearing failure: If the characteristic frequency of the bearing (such as outer ring, inner ring, rolling element failure frequency) and its harmonics are prominent in the spectrum, and accompanied by an increase in the random noise floor, it points to bearing damage.
Resonance failure: a spike appears at a specific frequency, the amplitude at the natural frequency is abnormally large, and the noise decreases significantly after deviating from this speed.
Unbalance/misalignment: If 1x rotational frequency vibration dominates, it may be due to misalignment of the coupling, bent shaft or unbalanced rotor.
3. Transfer Path Analysis (TPA)
When faced with complex vibration and noise problems caused by multi-source coupling, transfer path analysis (TPA) technology can be used to quantify the contribution relationship of "excitation source-transmission path-response point":
Path identification: Divide the vibration transmission path into a structural path (gear-bearing-box-base) and an air path (direct radiation of gear noise).
Contribution sorting: By arranging multiple acceleration sensors and rotational speed sensors to collect data synchronously, a contribution cloud diagram is generated, and the energy proportion of each path in a specific frequency band (such as gear meshing frequency) is intuitively identified, thereby accurately locking the noise radiation area and main fault sources.
4. Comprehensive parameter investigation and disassembly verification
After locking the general direction, perform cross-validation in combination with other operating parameters:
Temperature and lubrication inspection: Use an infrared thermometer to measure the surface temperature of the bearing seat and box (normally should be ≤80°C). Check whether the oil level is within the scale range and whether the oil is black, has metal shavings or is emulsified. Poor lubrication or insufficient oil film thickness can significantly increase noise.
Installation and alignment inspection: Confirm whether the foundation bolts are loose, and check the coaxiality of the motor and reducer (excessive angular deviation such as >0.1mm/100mm will cause vibration).
Disassembly verification: If the above analysis points to an internal mechanical failure, it must be disassembled in the order of "from outside to inside". Focus on checking gear tooth surface wear/pitting, bearing clearance and rotation, shaft curvature, and seal status to ultimately identify the root cause of the failure.
