Plastic gears — machined from acetal (POM) or nylon, or injection molded in glass-filled grades — now power everything from automotive window regulators to medical pumps. They run quieter, require no lubrication, and cost a fraction of metal gears when manufactured in volume.
Why Plastic Gears Replace Metal
Acetal and nylon gears are self-lubricating — the material itself provides the low-friction surface that in metal gears requires an external lubricant film. Plastic gears also absorb vibration instead of transmitting it, cutting drivetrain noise by 10-15 dB compared to steel gears. In applications where a motor pinion drives a large output gear, the plastic gear isolates motor vibration and significantly extends the motor’s bearing life.
Manufacturing Methods
- CNC Gear Hobbing: Dedicated gear hobbing machines cut tooth profiles into acetal or nylon blanks. Best for precision gears (AGMA 8-10 quality) in volumes of 10-1,000 units.
- CNC Milling: Standard 5-axis machining centers cut spur gears and helical gears. Suitable for prototypes and low volumes (1-100 units). Less cost-efficient than hobbing above 100 units.
- Injection Molding: For volumes above 1,000 units/year, molded gears with glass-filled nylon (PA66-GF30) offer the lowest per-part cost. Molded gear quality depends on maintaining precise mold temperature and consistent material drying.
Material Selection for Gears
Acetal (POM): Best all-around gear material. Low friction, excellent dimensional stability, negligible moisture absorption. Our default recommendation for precision gears under 150°C operating temperature.
Nylon 6/66: Higher temperature capability (180°C vs 150°C for acetal) and better impact resistance. The downside: nylon absorbs moisture and swells, so teeth must be designed with extra backlash for humid environments.
PEEK: For gears operating above 200°C or in chemically aggressive environments. Expensive (~$100/kg rod stock) but unmatched thermal and chemical performance.
Frequently Asked Questions
What gear quality can you achieve?
AGMA Q8-Q10 for hobbed plastic gears — comparable to commercial steel gear quality. Tooth-to-tooth composite error typically under 0.025mm. For molded gears, AGMA Q6-Q8 depending on mold quality and process control.
Will plastic gears wear out faster than metal?
Properly designed nylon or acetal gears within their PV (pressure-velocity) limit last as long as lubricated steel gears in many applications. The key is staying below the material’s PV limit — for acetal, roughly 0.12 MPa·m/s unlubricated. Exceed this and wear accelerates dramatically.
Can you manufacture helical and worm gears in plastic?
Yes — CNC hobbing produces helical, spur, and worm gear profiles in acetal and nylon rod stock. The hobbing process for plastic is identical to metal gear hobbing, using the same cutter geometry but optimized speeds.
What’s the minimum order for custom plastic gears?
We machine gears from prototype quantities (1-10 pcs) through production runs (100-10,000 pcs). For high volumes, we also manufacture injection molds for gear production and can manage the full transition from CNC prototype to molded production.
Need custom plastic gears?
From single prototypes to full production runs, we hob and injection mold acetal and nylon gears to your specifications.
