POM / Acetal Gears

POM / acetal gear family

POM/acetal is frequently evaluated for plastic gearing because of its dimensional behavior and low-friction characteristics, but grade, geometry, mating material and temperature still determine suitability.

POM can be sensitive to aggressive press fits and to thermal growth relative to a metal shaft. Where the bore is critical, state the shaft material, fit intent and assembly temperature. For dry-running pairs, the mating flank material and finish should be part of wear testing.

Geometry and interface inputs for POM / Acetal Gears

• Exact POM grade if specified
• Gear geometry and bore/hub interface
• Mating gear material
• Temperature, chemicals and lubrication
• Molding or machining quantity/route

Geometry reference: Spur, bevel and other supported functional gear forms

Choosing the production route

POM gears may be molded or machined. Molded geometry should account for shrinkage and hub/wall transitions, while machined gears depend on available stock form and stable fixturing.

Packaged process reference: Injection molding or machining according to confirmed product configuration

Material direction: POM / polyacetal / acetal

Application-specific design review

Press fits, elevated temperature or a mismatched wear pair can create performance issues even when the base resin is appropriate.

Typical use: Automation, appliances, office equipment and compact transmissions. The final material and tolerance plan should be checked against the load path, mating components and environment in that assembly.

First sample and inspection focus

Define gear geometry, bore/runout and any functional roll or mesh checks. Compare parts in a controlled temperature/conditioning state when dimensions are critical.

Quotation decision: Use the real operating temperature, moisture, mating material, torque, speed, geometry and tolerance needs to decide whether POM is suitable.

What to send for a POM / Acetal Gears quotation

Send the latest drawing or CAD model together with production quantity and the application conditions that affect fit, wear or dimensional stability. If the part replaces an existing component, identify the features that must remain interchangeable and any known field issue the new part is intended to solve.

• Controlled drawing revision and 3D model when available
• Mating-part or transmission geometry
• Material requirement or service environment
• Sample quantity, production batch and expected annual demand
• Critical dimensions and functional acceptance method

Engineering specification to freeze before manufacture

A production drawing should convert the application into measurable inputs. The table below is the minimum review set for this product family; add any assembly-specific datum, finish or acceptance requirement that changes function.

Failure modes to prevent during design review

Common risks for this geometry include grade substitution without rechecking shrinkage or dimensions; service moisture/temperature outside the approval condition; wear-pair assumptions based on one material only. These are best addressed before the first sample by reviewing the complete mating interface, not by tightening every drawing tolerance.

Use tolerances selectively. Dimensions that establish the tooth mesh, chain engagement, shaft fit or assembly datum deserve explicit measurement methods; non-critical molded surfaces can often use a more practical general tolerance.

First-article and production acceptance

Agree the inspection condition, datums and measuring method before sampling. The first-article report should cover the drawing CTQs and then be paired with a functional check in the real assembly or a representative fixture. For gears and sprockets, that can include mesh or chain engagement, runout and bore relationship; for custom molded parts it can include fit, fastening and loaded features.

Production control should follow the same CTQs rather than replacing them with a long list of easy-to-measure cosmetic dimensions. If a bore, tooth, insert or mounting surface is secondary-machined, make clear which operation establishes the final datum.

POM / Acetal Gears FAQ