Essential Knowledge About Gears: Types, Materials, Applications & Maintenance

1. Common Gear Types & Their Applications

• Spur Gears: Featuring straight teeth aligned parallel to the gear axis, they offer high transmission efficiency but generate more noise. Ideal for general machinery like pumps, conveyors, and simple gearboxes .

• Helical Gears: With spiral-shaped teeth, they engage smoothly with reduced noise and higher load-bearing capacity. Commonly used in high-speed, high-load systems such as car transmissions and wind turbines .

• Bevel Gears: Designed to connect intersecting shafts, they come in straight-tooth and spiral-tooth variants. Straight bevel gears suit low-speed applications like hand drills, while spiral bevel gears (quieter and more stable) are used in aerospace and marine machinery .

• Worm Gears: Comprising a worm (screw-like component) and a worm wheel, they provide high reduction ratios and self-locking functionality to prevent reverse rotation. Perfect for lifts, conveyors, and precision instruments .

• Rack and Pinion: Converts rotational motion into linear motion (or vice versa). Widely applied in car steering systems, linear actuators, and CNC machine tools .

• Planetary Gears: Consisting of a central sun gear, surrounding planet gears, and a ring gear, they offer compact size, high torque density, and versatile speed control. Used in EV drivetrains, automatic transmissions, and robotics .

2. Key Gear Materials & Selection Criteria

• Forged Steel: The preferred choice for high-performance gears, available in soft-tooth (HB < 350) and hard-tooth (HB > 350) variants. Materials like 40Cr and 20CrMnTi offer excellent strength and toughness, suitable for automotive, 机床，and aerospace gears .

• Cast Steel/Iron: Cast steel (e.g., ZG45) is used for large, complex-shaped gears (diameter > 400mm) where forging is impractical. Cast iron (e.g., gray iron) excels in anti-corrosion and cost-effectiveness, ideal for low-speed, light-load open transmissions .

• Non-Metallic Materials: Nylon, plastic, and wood are used for high-speed, light-load, low-noise applications. Common in food machinery, medical devices, and small appliances .

• Special Alloys: Stainless steel and copper alloys offer corrosion resistance and high thermal conductivity, suitable for harsh environments like marine or chemical equipment .

3. Common Gear Failures & Prevention

• Tooth Pitting: Small pits form on the tooth surface due to repeated contact stress. Prevent by using high-hardness materials, high-viscosity lubricants, and reducing surface roughness .

• Tooth Wear: Caused by friction or debris in the transmission. Mitigate with proper lubrication, closed transmission designs, and hardening treatments .

• Tooth Gluing: Metal adhesion between teeth due to insufficient lubrication and high temperatures. Avoid by using anti-gluing additives, different material combinations, and improving cooling .