The machining accuracy testing of hardened gear reducers is a systematic project that runs through the entire manufacturing process from raw materials to finished product assembly. The testing methods can be mainly divided into two categories: process testing and finished product testing to ensure that all indicators of the gear after processing, heat treatment and assembly can meet the design requirements.
1. Process testing
Process inspection is carried out during the gear processing and heat treatment stages, with the purpose of detecting and correcting deviations in time to ensure final accuracy.
1. Geometric accuracy detection
This is a measurement of the individual tooth profiles and overall geometric parameters of the gear.
Geometric accuracy testing items: Mainly include tooth shape error, tooth direction (spiral) error, tooth pitch cumulative error, radial runout, etc.
Geometric accuracy testing equipment: High-precision gear measurement centers are usually used. This type of equipment can automatically scan the tooth surface, accurately measure various deviations, and compare it with international standards (such as ISO, DIN, GB).
Accuracy requirements: For high-precision reducer gears (such as 6-7 level accuracy), the total deviation of tooth shape and tooth direction is usually required to be controlled at the micron (μm) level.
2. Material and heat treatment testing
The performance of hardened gears depends largely on the quality of the heat treatment.
Material and heat treatment testing items:
Surface hardness: Test the hardness of the tooth surface after carburizing and quenching. It is usually required to be in the range of 58-62 HRC.
Depth of hardened layer: Ensure that the depth of the hardened layer meets the design requirements (such as ≥0.8mm) to ensure the load-bearing capacity and fatigue life of the gear.
Metallographic structure: Observe the organizational morphology of the carburized layer through a metallographic microscope to ensure that there is no abnormal structure.
Material and heat treatment testing equipment: Rockwell hardness tester, Vickers hardness tester, metallographic microscope, etc.
3. Tooth surface roughness detection
The smoothness of the tooth surface directly affects the smoothness and wear resistance of the transmission.
Tooth surface roughness testing items: Measure the arithmetic mean deviation (Ra value) of the tooth surface profile.
Tooth surface roughness accuracy requirements: The tooth surface roughness Ra value of high-precision hard tooth surface gears is usually required to be controlled between 0.4-0.8 μm.
Tooth surface roughness testing equipment: stylus surface roughness meter.
2. Finished product testing
Finished product inspection is a comprehensive inspection performed after the reducer is assembled to verify its overall performance.
1. Contact spot detection (tooth grinding)
This is the most intuitive and critical method to evaluate the meshing quality of gear pairs.
Contact spot detection method: Apply red red powder or special colorant evenly on the tooth surface of the high-speed gear, and then rotate the reducer at low speed in forward and reverse directions to mesh the gears. After parking the vehicle, observe the contact marks left on the tooth surface of the driven gear.
Evaluation criteria: The contact spots should reach a certain proportion along the tooth length direction and tooth height direction, for example, ≥70% in the tooth length direction and ≥50% in the tooth height direction. If contact is poor, the gears may need to be paired ground.
