Gear finishing processes: What is gear burnishing primarily used for in manufacturing practice?
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ASurface finishing
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BUnder-cut gears
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CCycloidal gears
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DRemoving residual stresses from teeth roots
Answer
Correct Answer: Surface finishing
Explanation
Introduction / Context:After gear tooth generation (hobbing, shaping), finishing processes improve surface texture, contact pattern, and noise performance. Burnishing is a chip-less cold working technique performed with hardened gear-like tools.
Given Data / Assumptions:
- Process occurs after basic tooth form exists.
- Burnishing tools are harder than the work gear and roll in mesh.
- No abrasive is used; the method relies on plastic deformation at asperities.
Concept / Approach:Burnishing smooths the flanks by plastically deforming surface peaks into valleys, reducing roughness, improving bearing area, and sometimes inducing beneficial compressive stresses near the surface for better pitting resistance.
Step-by-Step Solution:
Mount the gear and burnishing tool; mesh under controlled pressure.As they roll, localized yielding flattens asperities → lower Ra.Contact pattern improves; running-in is effectively performed off-line.Result: enhanced surface finish and reduced noise during service.Verification / Alternative check:Surface measurements before/after show reduced roughness; tooth contact analysis indicates improved pattern and load distribution.
Why Other Options Are Wrong:
- Under-cut gears and cycloidal gears describe geometry, not a finishing process.
- Residual stress removal is linked to thermal stress relief; burnishing typically adds near-surface compressive stress rather than removing it.
Common Pitfalls:Confusing burnishing with lapping or honing (abrasive methods). Burnishing is chip-less and relies on plastic flow.
Final Answer:Surface finishing