Gear failures typically occur due to tooth breakage, surface fatigue, wear, or plastic deformation. Understanding these failure modes allows custom gear designers to implement preventive measures. Tooth breakage (bending fatigue) happens when applied stress exceeds the material’s endurance limit.
- Prevention: increase root fillet radius, use stronger materials (e.g., alloy steel instead of carbon steel), add shot peening to induce compressive residual stress, or increase face width. Pitting (surface fatigue) appears as small craters on tooth flanks due to repeated contact stress.
- Prevention: specify a higher hardness (e.g., 58–62 HRC instead of 40–45 HRC), use surface treatments like nitriding, improve lubrication filtration, or increase the pressure angle to reduce contact stress. Scoring occurs when lubricant film breaks down, causing local welding and tearing.
- Prevention: use profile crowning to reduce edge loading, specify smoother surface finishes (e.g., grinding to 0.4 µm Ra), or select anti-scoring materials like bronze for worm gears. Abrasive wear results from contaminated lubricant.
- Prevention: design for adequate filtration access and specify harder tooth surfaces. Overload deformation (cold flowing) happens when loads exceed yield strength.
- Prevention: increase module (tooth size) or use through-hardened steel instead of case-hardened where impact loads dominate.
By analyzing your application’s torque, speed, duty cycle, and environment, a custom gear manufacturer can optimize geometry, material, heat treatment, and surface finish to address these specific failure risks before production begins.