What are the machining methods for automotive gears?

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Gear hobbing: the most widely used method for rough machining external gears, which employs a hob and the workpiece’s generating motion to cut the gear tooth profile. It is highly efficient and cost-effective, making it suitable for cylindrical gears.

　　Shaving: Primarily used for internal gears, multi‑toothed gearsets, or applications where hobbing is impractical due to structural constraints; it involves the reciprocating up-and-down motion of a shaving cutter to perform the cutting operation.

　　Shaving: A finishing process performed prior to heat treatment, it employs the principle of free meshing to remove a small amount of stock, improving accuracy by 1–2 grades. While cost-effective, it cannot correct deformation caused by heat treatment.

　　Gear grinding: A high-precision finishing process performed after heat treatment, using a grinding wheel to correct tooth profile and helix errors. It can achieve accuracy levels of ISO 5 or higher, making it suitable for high-speed applications with stringent noise requirements; however, it comes at a relatively high cost.

　　Honing: A surface finishing process performed after heat treatment, in which an abrasive honing wheel engages with the gear to produce an intersecting cross‑hatch pattern, thereby enhancing lubrication and reducing noise, vibration, and harshness (NVH). It features low cutting forces and no thermal damage, making it widely used for gears in new‑energy vehicles.

　　Honing: Primarily used for the post‑heat finishing of spiral bevel gears, it achieves minute material removal via a honing compound. Its geometric correction capability is inferior to that of gear grinding, but its efficiency is relatively higher.

　　Gear milling/gear shaping: Primarily used for the form‑cutting of bevel gears—whether straight‑toothed or helical—relying on specialized machine tools and tool systems, such as the Gleason or Oerlikon systems.

　　Rolling (cold rolling/hot rolling): A chip-free forming process in which metal is plastically deformed by the action of rolls, producing gear teeth. It offers high productivity and yields continuous metal flow lines with superior strength, making it particularly suitable for small‑module gears.