What are the reasons for poor contact of gears in ZLY250-21.73-II reducer

The reasons for poor contact of gears in ZLY250-21.73-II reducer can be summarized into four categories: substandard manufacturing accuracy of components, assembly process deviation, improper lubrication and maintenance, and problems with working conditions and installation foundations, as follows:

1. Precision defects in component manufacturing

Gear machining errors: Accumulated errors in tooth profile, tooth direction, and tooth pitch exceed the design accuracy requirement of level 6, and the tooth surface roughness Ra value is too large, resulting in uneven contact during meshing; The deformation of the gear after carburizing and quenching is not corrected, and the tooth surface is warped.

Box processing deviation: The coaxiality and parallelism of the bearing holes exceed the tolerance (allowable value ≤ 0.02mm/m), and the center distance deviation exceeds the design range, resulting in gear axis position deviation and biased load during meshing.

Insufficient bearing accuracy: Select bearings with accuracy lower than P5 level, or bearings with excessive/insufficient clearance, causing shaft movement or tilting during operation, and damaging the gear meshing position.

2. Deviation in assembly process operation

Inappropriate axis calibration: During assembly, the parallelism of the input and output shafts was not calibrated using a laser tracker or precision level, or the thickness error of the gear axial positioning gasket was too large, resulting in biased contact in the tooth width direction.

Inadequate cleaning of components: residual iron filings, burrs, and oil stains on the tooth surface and bearing holes, foreign objects trapped on the meshing surface after assembly, causing stress concentration at local contact points and uneven distribution of spots.

Loose fasteners: The gear locking nut and bearing end cap bolt are not tightened to the specified torque, causing axial movement of the gear or displacement of the shaft system during operation, resulting in fluctuations in the contact state.

3. Improper lubrication and maintenance management

Incorrect selection of lubricating oil: Improper use of suitable extreme pressure gear oil (recommended L-CKD 320/460), insufficient viscosity of the oil or absence of extreme pressure additives, inability to form a stable oil film on the tooth surface, resulting in dry or semi dry friction.

Oil contamination and deterioration: The cleanliness of the oil does not meet the NAS level 8 standard, and impurities enter the tooth surface, causing abrasive wear; If the lubricating oil is not replaced for a long time, its lubrication performance will decrease after oxidation and deterioration, which will damage the contact state.

Abnormal oil level: Excessive oil level leads to high stirring resistance and increased oil temperature, while insufficient lubrication of the tooth surface can cause local poor contact.