Gear
Manufacture

The most common techniques for gear manufacturing are dies, sand, and investment casting; injection molding; powder metallurgy; blanking; and gear cutting.

As of 2014, an estimated 80% of all gearing produced worldwide is produced by net shape molding. Molded gearing is usually powder metallurgy, plastic injection, or metal die casting. Gears produced by powder metallurgy often require a sintering step after they are removed from the mold. Cast gears require gear cutting or other machining to shape the teeth to the necessary precision. The most common form of gear cutting is hobbing, but gear shaping, milling, and broaching may be used instead.

Metal gears intended for heavy duty operation, such as in the transmissions of cars and trucks, the teeth are heat treated to make them hard and more wear resistant while leaving the core soft but tough. For large gears that are prone to warp, a quench press is used.

Gears can be made by 3D printing; however, this alternative is typically used only for prototypes or very limited production quantities, because of its high cost, low accuracy, and relatively low strength of the resulting part.
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