Abstract:
Gear shaving, as a precision machining process, significantly impacts the meshing noise and strength of gears due to its accuracy. Our company identified tooth surface distortion issues during the gear shaving process. To address this, we developed an experimental scheme, collected data on various variables related to distortion through controlled single-variable testing, analyzed these data in conjunction with gear shaving principles, summarized a theoretical model for gear shaving distortion, and formulated solutions based on this model. Ultimately, we resolved the issue of tooth surface distortion in gear shaving.
1. Problem Description
The gear shaving process in our factory resulted in tooth surface distortion upon inspection of three cross-sections of the gears post-shaving. Converting the inspection report into a 3D model of the gear revealed the distortion. This distortion leads to two hazards during gear meshing: firstly, it causes the meshing point to shift in the tooth direction, resulting in gear misalignment and torque, which affects gear strength and lifespan. Secondly, it alters the actual tooth profile of the gear, impacting meshing noise.
2. Factors Influencing Gear Shaving Distortion
We identified potential factors influencing tooth surface distortion in gear shaving and established their hierarchical relationships. By locking all other variables and varying one at a time, we tested the distortion amount of the shaved gears to determine the relationship between each variable parameter and distortion. Through successive testing of each variable, we identified all factors influencing gear shaving distortion, analyzed them comprehensively with gear shaving principles, derived a theory of gear shaving distortion, and ultimately formulated solutions.
3. Experimental Procedure
Table 1: Verification of the Impact of Shaving Cutters on Distortion
| Tool Helix Angle | Distortion Amount (μm) |
|---|---|
| 10° | Data 1 |
| 12° | Data 2 |
| 15° | Data 3 |
(Note: Actual data values would be filled in here.)
The test results showed no inherent distortion in the cutting tools, indicating that the distortion in our products was not caused by distorted tools. The relationship between distortion amount and tool helix angle. As the helix angle increases, so does the distortion amount.
Similar experiments were conducted to verify the impact of shaving equipment, shaving types, cutting parameters, and gear modification parameters on distortion. The results are summarized.
4. Experimental Data Summary
Through the experiments, we drew the conclusion. Distortion only occurs with radial shaving, and the two influencing factors are the tooth flank crown amount and the tool helix angle. The difference between radial and axial shaving lies in the concave tooth flank amount of radial shaving tools. Therefore, the factors causing gear shaving distortion are summarized as: the tooth flank crown amount of the gear and the helix angle of the shaving cutter.
5. Theory of Gear Shaving Distortion
The principle of gear shaving involves a pair of gears meshing with relative tangential sliding motion between the tooth surfaces. The shaving cutter is manufactured to correctly mesh with the gear being processed, with a helix angle differing from that of the gear by a certain angle, known as the axis intersection angle. This results in axial component sliding during meshing, and scraping of the gear in the axial direction with teeth perpendicular to the axial direction.
The formula for calculating gear shaving distortion involves various parameters such as axial sliding amount (a), relative sliding amount of tooth surface (s), length of the meshing line (P), axis intersection angle (β), and others. The detailed formula and derivations are provided, indicating that gear shaving distortion is positively correlated with gear width, tooth flank crown amount, and tool helix angle.
6. Solutions to Gear Shaving Distortion
Based on the analysis, solutions to gear shaving distortion include:
- Eliminating radial shaving and using axial shaving.
- Not applying tooth flank crown to gears.
- Minimizing the tool helix angle to reduce distortion within an acceptable range.
- Applying reverse distortion grinding to the shaving cutter to compensate for the distortion and achieve the desired tooth surface.
Considering the efficiency and cost implications, our company chose to apply reverse distortion grinding to the shaving cutters.
Table 5: Summary of Solution Options
| Solution Option | Pros | Cons |
|---|---|---|
| Eliminate radial shaving | Eliminates distortion | Reduces production capacity, increases cost |
| No tooth flank crown | Eliminates distortion | Not feasible for design requirements |
| Minimize tool helix angle | Reduces distortion | Lowers cutting performance |
| Reverse distortion grinding | Compensates distortion | Requires precision grinding process |
The tool was ground with a base circle cylinder eccentricity during the meshing process between the shaving cutter and grinding wheel, causing distortion on the tooth surface of the shaving cutter. The grinding process simulated the meshing of helical gears, with the difference being that the relative motion was achieved solely by the tool.
7. Conclusion
By adopting a controlled single-variable experimental scheme to examine the relationship between each variable and gear shaving distortion, we identified the factors influencing distortion. Combining data analysis with gear shaving principles, we formulated a theory of gear shaving distortion and developed solutions based on this theory, ultimately resolving the issue of tooth surface distortion in gear shaving.
The research and solution process highlights the importance of systematic experimentation, data analysis, and theoretical modeling in addressing complex manufacturing issues, particularly in precision machining processes such as gear shaving.