How to determine whether the alignment of the multi-stage reducer is good

To determine whether the centering of the multi-stage reducer is the core of detecting the relative position deviation of the axis of the input shaft, intermediate shafts at each stage, and output shaft (including parallelism and coaxiality), as well as the neutrality between the shaft and the coupling (or motor shaft) . Poor centering will lead to gear bias load, bearing overheating, and vibration abnormalities, which will shorten the life in the long run. The following are three aspects: 'Basic inspection (fast judgment)''Professional inspection (precise quantification)''''Centering bad characteristics' and provide ground-based judgment methods, covering on-site operation and professional tool application scenarios:

1. Basic inspection: No professional tools are required, quickly identify obvious bad habits

Suitable for daily inspections or preliminary investigations, and judge abnormalities through 'see, listen, touch, and test', with low operating threshold:

1. Observe appearance and component status

• Gear meshing traces : Open the reducer observation hole (requires shutdown and power outage), check the meshing contact spots of gears at all levels (can be applied to reddish powder for assisting observation):

• Good centering: The contact spots are evenly distributed in the middle of the tooth surface, accounting for more than 60% of the width of the tooth surface (cylindrical gear) or more than 50% of the tooth height (bevel gear);

• Centering poor: The contact spots are biased to one end of the tooth surface (such as toward the tooth top/root, or the side of the tooth width), or 'edge contact' occurs (only there are traces on the edge of the tooth surface), indicating that the axis parallelism deviation exceeds the standard.

• Shaft and radial jump : gently shake the coupling or shaft end (stop state) with your hand. If you feel obvious squirming (axial) or radial shaking, it may be due to bearing wear and the shaft system offset, which indirectly reflects the centering problem.

2. Monitor vibration and noise during operation

• Vibration judgment : Touch the reducer case with your hand (after running for 1 hour), if a certain bearing seat area vibrates significantly (compared with other bearing seats), or the overall vibration frequency is accompanied by 'periodic abnormal noise' (such as the meshing impact sound of 'clogs and clacks', it may be due to poor centering of the shaft system, which leads to uneven gear meshing clearance;

• Noise judgment : During normal centering, the operating noise of the reducer is 'uniform gear meshing sound'; if there is a 'sharp and harsh sound' (the biased load causes local wear on the tooth surface) or a 'low frequency roar' (the axis offset causes uneven bearing force), further inspection and centering are required.

3. Test bearing and oil temperature

• Bearing temperature : Use an infrared thermometer to measure the temperature of bearing seats at each level (after running for 30 minutes). When the centering is good, the temperature difference between the bearings on the same side should be ≤5℃; if the temperature of a certain bearing is significantly higher (such as exceeding the ambient temperature of 40℃, or above 10℃ higher than other bearings), it may be due to poor centering of the shaft system, which leads to excessive radial force of the bearing and intensifying friction;

• Changes in oil temperature : Poor centering will lead to an increase in gear meshing resistance and accelerate the oil temperature rise - Under normal operating conditions, the oil temperature is stable at 40-60℃; if the oil temperature continues to exceed 70℃ (no heavy load and normal ambient temperature), the problem of centering needs to be checked (at the same time, the poor lubrication factors are eliminated).

  
  

2. Professional testing: Accurately quantify the centering deviation, requiring tool assistance

When basic inspections suspect bad alignment, professional tools need to be used to quantify deviations (commonly after new machine installation, overhaul or vibration abnormalities), core detection 'axis parallelism' and 'coupling neutral':

1. Coupling neutral detection (connection with external devices for input/output shaft)

The input shaft of the multi-stage reducer is often connected to the motor coupling, and the output shaft is connected to the load (such as rollers, gear boxes) coupling. These two centering defects will be directly transmitted to the internal shaft system and need to be tested with a focus. Common tools are

Dial meter (dial meter) + magnetic meter holder

, the detection methods are divided into 'radial deviation' and 'end surface deviation':

Example : If the coupling diameter is 200mm, the total radial deviation must be ≤0.02mm (0.1mm/m × 0.2m), and the total end face deviation must be ≤0.01mm (0.05mm/m × 0.2m).

2. Internal shaft system parallelism detection (for multi-stage gear shafts)

There are 2-3 intermediate shafts (such as high-speed shaft, medium-speed shaft, and low-speed shaft) inside the multi-stage reducer. The parallelism of adjacent shafts (cylindrical gear transmission) or coaxiality (bevel gear transmission). Common tools are

Laser centering instrument

(High precision) or

Sharpener + ruler

(simple):

• Laser centering method (recommended, accuracy 0.001mm):

1. Install laser emitter and receiver respectively at the shaft ends of the adjacent two axes;

2. When rotating the shaft system, the laser will display the 'parallelism deviation' (X/Y direction) and 'axial offset' of the two axes in real time;

3. Qualification criteria: parallelism deviation ≤0.05mm/m, axial deviation ≤0.03mm/m (the requirements for hard tooth surface reducers are stricter, and they need to be ≤0.03mm/m).